__GFP_REPEAT was designed to allow retry-but-eventually-fail semantic to
the page allocator. This has been true but only for allocations
requests larger than PAGE_ALLOC_COSTLY_ORDER. It has been always
ignored for smaller sizes. This is a bit unfortunate because there is
no way to express the same semantic for those requests and they are
considered too important to fail so they might end up looping in the
page allocator for ever, similarly to GFP_NOFAIL requests.
Now that the whole tree has been cleaned up and accidental or misled
usage of __GFP_REPEAT flag has been removed for !costly requests we can
give the original flag a better name and more importantly a more useful
semantic. Let's rename it to __GFP_RETRY_MAYFAIL which tells the user
that the allocator would try really hard but there is no promise of a
success. This will work independent of the order and overrides the
default allocator behavior. Page allocator users have several levels of
guarantee vs. cost options (take GFP_KERNEL as an example)
- GFP_KERNEL & ~__GFP_RECLAIM - optimistic allocation without _any_
attempt to free memory at all. The most light weight mode which even
doesn't kick the background reclaim. Should be used carefully because
it might deplete the memory and the next user might hit the more
aggressive reclaim
- GFP_KERNEL & ~__GFP_DIRECT_RECLAIM (or GFP_NOWAIT)- optimistic
allocation without any attempt to free memory from the current
context but can wake kswapd to reclaim memory if the zone is below
the low watermark. Can be used from either atomic contexts or when
the request is a performance optimization and there is another
fallback for a slow path.
- (GFP_KERNEL|__GFP_HIGH) & ~__GFP_DIRECT_RECLAIM (aka GFP_ATOMIC) -
non sleeping allocation with an expensive fallback so it can access
some portion of memory reserves. Usually used from interrupt/bh
context with an expensive slow path fallback.
- GFP_KERNEL - both background and direct reclaim are allowed and the
_default_ page allocator behavior is used. That means that !costly
allocation requests are basically nofail but there is no guarantee of
that behavior so failures have to be checked properly by callers
(e.g. OOM killer victim is allowed to fail currently).
- GFP_KERNEL | __GFP_NORETRY - overrides the default allocator behavior
and all allocation requests fail early rather than cause disruptive
reclaim (one round of reclaim in this implementation). The OOM killer
is not invoked.
- GFP_KERNEL | __GFP_RETRY_MAYFAIL - overrides the default allocator
behavior and all allocation requests try really hard. The request
will fail if the reclaim cannot make any progress. The OOM killer
won't be triggered.
- GFP_KERNEL | __GFP_NOFAIL - overrides the default allocator behavior
and all allocation requests will loop endlessly until they succeed.
This might be really dangerous especially for larger orders.
Existing users of __GFP_REPEAT are changed to __GFP_RETRY_MAYFAIL
because they already had their semantic. No new users are added.
__alloc_pages_slowpath is changed to bail out for __GFP_RETRY_MAYFAIL if
there is no progress and we have already passed the OOM point.
This means that all the reclaim opportunities have been exhausted except
the most disruptive one (the OOM killer) and a user defined fallback
behavior is more sensible than keep retrying in the page allocator.
[akpm@linux-foundation.org: fix arch/sparc/kernel/mdesc.c]
[mhocko@suse.com: semantic fix]
Link: http://lkml.kernel.org/r/20170626123847.GM11534@dhcp22.suse.cz
[mhocko@kernel.org: address other thing spotted by Vlastimil]
Link: http://lkml.kernel.org/r/20170626124233.GN11534@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20170623085345.11304-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alex Belits <alex.belits@cavium.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: David Daney <david.daney@cavium.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: NeilBrown <neilb@suse.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrey reported a potential deadlock with the memory hotplug lock and
the cpu hotplug lock.
The reason is that memory hotplug takes the memory hotplug lock and then
calls stop_machine() which calls get_online_cpus(). That's the reverse
lock order to get_online_cpus(); get_online_mems(); in mm/slub_common.c
The problem has been there forever. The reason why this was never
reported is that the cpu hotplug locking had this homebrewn recursive
reader writer semaphore construct which due to the recursion evaded the
full lock dep coverage. The memory hotplug code copied that construct
verbatim and therefor has similar issues.
Three steps to fix this:
1) Convert the memory hotplug locking to a per cpu rwsem so the
potential issues get reported proper by lockdep.
2) Lock the online cpus in mem_hotplug_begin() before taking the memory
hotplug rwsem and use stop_machine_cpuslocked() in the page_alloc
code to avoid recursive locking.
3) The cpu hotpluck locking in #2 causes a recursive locking of the cpu
hotplug lock via __offline_pages() -> lru_add_drain_all(). Solve this
by invoking lru_add_drain_all_cpuslocked() instead.
Link: http://lkml.kernel.org/r/20170704093421.506836322@linutronix.de
Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since current_order starts as MAX_ORDER-1 and is then only decremented,
the second half of the loop condition seems superfluous. However, if
order is 0, we may decrement current_order past 0, making it UINT_MAX.
This is obviously too subtle ([1], [2]).
Since we need to add some comment anyway, change the two variables to
signed, making the counting-down for loop look more familiar, and
apparently also making gcc generate slightly smaller code.
[1] https://lkml.org/lkml/2016/6/20/493
[2] https://lkml.org/lkml/2017/6/19/345
[akpm@linux-foundation.org: fix up reject fixupping]
Link: http://lkml.kernel.org/r/20170621185529.2265-1-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reported-by: Hao Lee <haolee.swjtu@gmail.com>
Acked-by: Wei Yang <weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 3bc48f96cf ("mm, page_alloc: split smallest stolen page
in fallback") we pick the smallest (but sufficient) page of all that
have been stolen from a pageblock of different migratetype. However,
there are cases when we decide not to steal the whole pageblock.
Practically in the current implementation it means that we are trying to
fallback for a MIGRATE_MOVABLE allocation of order X, go through the
freelists from MAX_ORDER-1 down to X, and find free page of order Y. If
Y is less than pageblock_order / 2, we decide not to steal all pages
from the pageblock. When Y > X, it means we are potentially splitting a
larger page than we need, as there might be other pages of order Z,
where X <= Z < Y. Since Y is already too small to steal whole
pageblock, picking smallest available Z will result in the same decision
and we avoid splitting a higher-order page in a MIGRATE_UNMOVABLE or
MIGRATE_RECLAIMABLE pageblock.
This patch therefore changes the fallback algorithm so that in the
situation described above, we switch the fallback search strategy to go
from order X upwards to find the smallest suitable fallback. In theory
there shouldn't be a downside of this change wrt fragmentation.
This has been tested with mmtests' stress-highalloc performing
GFP_KERNEL order-4 allocations, here is the relevant extfrag tracepoint
statistics:
4.12.0-rc2 4.12.0-rc2
1-kernel4 2-kernel4
Page alloc extfrag event 25640976 69680977
Extfrag fragmenting 25621086 69661364
Extfrag fragmenting for unmovable 74409 73204
Extfrag fragmenting unmovable placed with movable 69003 67684
Extfrag fragmenting unmovable placed with reclaim. 5406 5520
Extfrag fragmenting for reclaimable 6398 8467
Extfrag fragmenting reclaimable placed with movable 869 884
Extfrag fragmenting reclaimable placed with unmov. 5529 7583
Extfrag fragmenting for movable 25540279 69579693
Since we force movable allocations to steal the smallest available page
(which we then practially always split), we steal less per fallback, so
the number of fallbacks increases and steals potentially happen from
different pageblocks. This is however not an issue for movable pages
that can be compacted.
Importantly, the "unmovable placed with movable" statistics is lower,
which is the result of less fragmentation in the unmovable pageblocks.
The effect on reclaimable allocation is a bit unclear.
Link: http://lkml.kernel.org/r/20170529093947.22618-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 20b2f52b73 ("numa: add CONFIG_MOVABLE_NODE for
movable-dedicated node") has introduced CONFIG_MOVABLE_NODE without a
good explanation on why it is actually useful.
It makes a lot of sense to make movable node semantic opt in but we
already have that because the feature has to be explicitly enabled on
the kernel command line. A config option on top only makes the
configuration space larger without a good reason. It also adds an
additional ifdefery that pollutes the code.
Just drop the config option and make it de-facto always enabled. This
shouldn't introduce any change to the semantic.
Link: http://lkml.kernel.org/r/20170529114141.536-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Kani Toshimitsu <toshi.kani@hpe.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm: per-lruvec slab stats"
Josef is working on a new approach to balancing slab caches and the page
cache. For this to work, he needs slab cache statistics on the lruvec
level. These patches implement that by adding infrastructure that
allows updating and reading generic VM stat items per lruvec, then
switches some existing VM accounting sites, including the slab
accounting ones, to this new cgroup-aware API.
I'll follow up with more patches on this, because there is actually
substantial simplification that can be done to the memory controller
when we replace private memcg accounting with making the existing VM
accounting sites cgroup-aware. But this is enough for Josef to base his
slab reclaim work on, so here goes.
This patch (of 5):
To re-implement slab cache vs. page cache balancing, we'll need the
slab counters at the lruvec level, which, ever since lru reclaim was
moved from the zone to the node, is the intersection of the node, not
the zone, and the memcg.
We could retain the per-zone counters for when the page allocator dumps
its memory information on failures, and have counters on both levels -
which on all but NUMA node 0 is usually redundant. But let's keep it
simple for now and just move them. If anybody complains we can restore
the per-zone counters.
[hannes@cmpxchg.org: fix oops]
Link: http://lkml.kernel.org/r/20170605183511.GA8915@cmpxchg.org
Link: http://lkml.kernel.org/r/20170530181724.27197-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The main allocator function __alloc_pages_nodemask() takes a zonelist
pointer as one of its parameters. All of its callers directly or
indirectly obtain the zonelist via node_zonelist() using a preferred
node id and gfp_mask. We can make the code a bit simpler by doing the
zonelist lookup in __alloc_pages_nodemask(), passing it a preferred node
id instead (gfp_mask is already another parameter).
There are some code size benefits thanks to removal of inlined
node_zonelist():
bloat-o-meter add/remove: 2/2 grow/shrink: 4/36 up/down: 399/-1351 (-952)
This will also make things simpler if we proceed with converting cpusets
to zonelists.
Link: http://lkml.kernel.org/r/20170517081140.30654-4-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Christoph Lameter <cl@linux.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I would like to stress that this patchset aims to fix issues and cleanup
the code *within the existing documented semantics*, i.e. patch 1
ignores mempolicy restrictions if the set of allowed nodes has no
intersection with set of nodes allowed by cpuset. I believe discussing
potential changes of the semantics can be better done once we have a
baseline with no known bugs of the current semantics.
I've recently summarized the cpuset/mempolicy issues in a LSF/MM
proposal [1] and the discussion itself [2]. I've been trying to rewrite
the handling as proposed, with the idea that changing semantics to make
all mempolicies static wrt cpuset updates (and discarding the relative
and default modes) can be tried on top, as there's a high risk of being
rejected/reverted because somebody might still care about the removed
modes.
However I haven't yet figured out how to properly:
1) make mempolicies swappable instead of rebinding in place. I thought
mbind() already works that way and uses refcounting to avoid
use-after-free of the old policy by a parallel allocation, but turns
out true refcounting is only done for shared (shmem) mempolicies, and
the actual protection for mbind() comes from mmap_sem. Extending the
refcounting means more overhead in allocator hot path. Also swapping
whole mempolicies means that we have to allocate the new ones, which
can fail, and reverting of the partially done work also means
allocating (note that mbind() doesn't care and will just leave part
of the range updated and part not updated when returning -ENOMEM...).
2) make cpuset's task->mems_allowed also swappable (after converting it
from nodemask to zonelist, which is the easy part) for mostly the
same reasons.
The good news is that while trying to do the above, I've at least
figured out how to hopefully close the remaining premature OOM's, and do
a buch of cleanups on top, removing quite some of the code that was also
supposed to prevent the cpuset update races, but doesn't work anymore
nowadays. This should fix the most pressing concerns with this topic
and give us a better baseline before either proceeding with the original
proposal, or pushing a change of semantics that removes the problem 1)
above. I'd be then fine with trying to change the semantic first and
rewrite later.
Patchset has been tested with the LTP cpuset01 stress test.
[1] https://lkml.kernel.org/r/4c44a589-5fd8-08d0-892c-e893bb525b71@suse.cz
[2] https://lwn.net/Articles/717797/
[3] https://marc.info/?l=linux-mm&m=149191957922828&w=2
This patch (of 6):
Commit e47483bca2 ("mm, page_alloc: fix premature OOM when racing with
cpuset mems update") has fixed known recent regressions found by LTP's
cpuset01 testcase. I have however found that by modifying the testcase
to use per-vma mempolicies via bind(2) instead of per-task mempolicies
via set_mempolicy(2), the premature OOM still happens and the issue is
much older.
The root of the problem is that the cpuset's mems_allowed and
mempolicy's nodemask can temporarily have no intersection, thus
get_page_from_freelist() cannot find any usable zone. The current
semantic for empty intersection is to ignore mempolicy's nodemask and
honour cpuset restrictions. This is checked in node_zonelist(), but the
racy update can happen after we already passed the check. Such races
should be protected by the seqlock task->mems_allowed_seq, but it
doesn't work here, because 1) mpol_rebind_mm() does not happen under
seqlock for write, and doing so would lead to deadlock, as it takes
mmap_sem for write, while the allocation can have mmap_sem for read when
it's taking the seqlock for read. And 2) the seqlock cookie of callers
of node_zonelist() (alloc_pages_vma() and alloc_pages_current()) is
different than the one of __alloc_pages_slowpath(), so there's still a
potential race window.
This patch fixes the issue by having __alloc_pages_slowpath() check for
empty intersection of cpuset and ac->nodemask before OOM or allocation
failure. If it's indeed empty, the nodemask is ignored and allocation
retried, which mimics node_zonelist(). This works fine, because almost
all callers of __alloc_pages_nodemask are obtaining the nodemask via
node_zonelist(). The only exception is new_node_page() from hotplug,
where the potential violation of nodemask isn't an issue, as there's
already a fallback allocation attempt without any nodemask. If there's
a future caller that needs to have its specific nodemask honoured over
task's cpuset restrictions, we'll have to e.g. add a gfp flag for that.
Link: http://lkml.kernel.org/r/20170517081140.30654-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The functions are not used in some configurations. Adding the attribute
fixes the following warnings when building with clang:
mm/page_alloc.c:409:19: error: function 'bad_range' is not needed and
will not be emitted [-Werror,-Wunneeded-internal-declaration]
mm/page_alloc.c:1106:30: error: unused function 'meminit_pfn_in_nid'
[-Werror,-Wunused-function]
Link: http://lkml.kernel.org/r/20170518182030.165633-1-mka@chromium.org
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Allow hash tables to scale with memory but at slower pace, when
HASH_ADAPT is provided every time memory quadruples the sizes of hash
tables will only double instead of quadrupling as well. This algorithm
starts working only when memory size reaches a certain point, currently
set to 64G.
This is example of dentry hash table size, before and after four various
memory configurations:
MEMORY SCALE HASH_SIZE
old new old new
8G 13 13 8M 8M
16G 13 13 16M 16M
32G 13 13 32M 32M
64G 13 13 64M 64M
128G 13 14 128M 64M
256G 13 14 256M 128M
512G 13 15 512M 128M
1024G 13 15 1024M 256M
2048G 13 16 2048M 256M
4096G 13 16 4096M 512M
8192G 13 17 8192M 512M
16384G 13 17 16384M 1024M
32768G 13 18 32768M 1024M
65536G 13 18 65536M 2048M
The effect of this change on runtime is undetectable as filesystem
growth is not proportional to machine memory size as is currently
assumed. The change effects only large memory machine. Additional
tuning might be needed, but that can be done by the clients of the
kmem_cache_create interface, not the generic cache allocator itself.
The adaptive hashing is disabled on 32 bit systems to avoid confusion of
whether base should be different for smaller systems, and to avoid
overflows.
[mhocko@suse.com: drop HASH_ADAPT]
Link: http://lkml.kernel.org/r/20170509094607.GG6481@dhcp22.suse.cz
[pasha.tatashin@oracle.com: UL -> ULL fix]
Link: http://lkml.kernel.org/r/1495300013-653283-2-git-send-email-pasha.tatashin@oracle.com
[pasha.tatashin@oracle.com: disable adaptive hash on 32 bit systems]
Link: http://lkml.kernel.org/r/1495469329-755807-2-git-send-email-pasha.tatashin@oracle.com
Link: http://lkml.kernel.org/r/1488432825-92126-5-git-send-email-pasha.tatashin@oracle.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Miller <davem@davemloft.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Babu Moger <babu.moger@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a new flag HASH_ZERO which when provided grantees that the hash
table that is returned by alloc_large_system_hash() is zeroed. In most
cases that is what is needed by the caller. Use page level allocator's
__GFP_ZERO flags to zero the memory. It is using memset() which is
efficient method to zero memory and is optimized for most platforms.
Link: http://lkml.kernel.org/r/1488432825-92126-3-git-send-email-pasha.tatashin@oracle.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Babu Moger <babu.moger@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__pageblock_pfn_to_page has two users currently, set_zone_contiguous
which checks whether the given zone contains holes and
pageblock_pfn_to_page which then carefully returns a first valid page
from the given pfn range for the given zone. This doesn't handle zones
which are not fully populated though. Memory pageblocks can be offlined
or might not have been onlined yet. In such a case the zone should be
considered to have holes otherwise pfn walkers can touch and play with
offline pages.
Current callers of pageblock_pfn_to_page in compaction seem to work
properly right now because they only isolate PageBuddy
(isolate_freepages_block) or PageLRU resp. __PageMovable
(isolate_migratepages_block) which will be always false for these pages.
It would be safer to skip these pages altogether, though.
In order to do this patch adds a new memory section state
(SECTION_IS_ONLINE) which is set in memory_present (during boot time) or
in online_pages_range during the memory hotplug. Similarly
offline_mem_sections clears the bit and it is called when the memory
range is offlined.
pfn_to_online_page helper is then added which check the mem section and
only returns a page if it is onlined already.
Use the new helper in __pageblock_pfn_to_page and skip the whole page
block in such a case.
[mhocko@suse.com: check valid section number in pfn_to_online_page (Vlastimil),
mark sections online after all struct pages are initialized in
online_pages_range (Vlastimil)]
Link: http://lkml.kernel.org/r/20170518164210.GD18333@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20170515085827.16474-8-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Tobias Regnery <tobias.regnery@gmail.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm: make movable onlining suck less", v4.
Movable onlining is a real hack with many downsides - mainly
reintroduction of lowmem/highmem issues we used to have on 32b systems -
but it is the only way to make the memory hotremove more reliable which
is something that people are asking for.
The current semantic of memory movable onlinening is really cumbersome,
however. The main reason for this is that the udev driven approach is
basically unusable because udev races with the memory probing while only
the last memory block or the one adjacent to the existing zone_movable
are allowed to be onlined movable. In short the criterion for the
successful online_movable changes under udev's feet. A reliable udev
approach would require a 2 phase approach where the first successful
movable online would have to check all the previous blocks and online
them in descending order. This is hard to be considered sane.
This patchset aims at making the onlining semantic more usable. First
of all it allows to online memory movable as long as it doesn't clash
with the existing ZONE_NORMAL. That means that ZONE_NORMAL and
ZONE_MOVABLE cannot overlap. Currently I preserve the original ordering
semantic so the zone always precedes the movable zone but I have plans
to remove this restriction in future because it is not really necessary.
First 3 patches are cleanups which should be ready to be merged right
away (unless I have missed something subtle of course).
Patch 4 deals with ZONE_DEVICE dependencies down the __add_pages path.
Patch 5 deals with implicit assumptions of register_one_node on pgdat
initialization.
Patches 6-10 deal with offline holes in the zone for pfn walkers. I
hope I got all of them right but people familiar with compaction should
double check this.
Patch 11 is the core of the change. In order to make it easier to
review I have tried it to be as minimalistic as possible and the large
code removal is moved to patch 14.
Patch 12 is a trivial follow up cleanup. Patch 13 fixes sparse warnings
and finally patch 14 removes the unused code.
I have tested the patches in kvm:
# qemu-system-x86_64 -enable-kvm -monitor pty -m 2G,slots=4,maxmem=4G -numa node,mem=1G -numa node,mem=1G ...
and then probed the additional memory by
(qemu) object_add memory-backend-ram,id=mem1,size=1G
(qemu) device_add pc-dimm,id=dimm1,memdev=mem1
Then I have used this simple script to probe the memory block by hand
# cat probe_memblock.sh
#!/bin/sh
BLOCK_NR=$1
# echo $((0x100000000+$BLOCK_NR*(128<<20))) > /sys/devices/system/memory/probe
# for i in $(seq 10); do sh probe_memblock.sh $i; done
# grep . /sys/devices/system/memory/memory3?/valid_zones 2>/dev/null
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Normal Movable
/sys/devices/system/memory/memory35/valid_zones:Normal Movable
/sys/devices/system/memory/memory36/valid_zones:Normal Movable
/sys/devices/system/memory/memory37/valid_zones:Normal Movable
/sys/devices/system/memory/memory38/valid_zones:Normal Movable
/sys/devices/system/memory/memory39/valid_zones:Normal Movable
The main difference to the original implementation is that all new
memblocks can be both online_kernel and online_movable initially because
there is no clash obviously. For the comparison the original
implementation would have
/sys/devices/system/memory/memory33/valid_zones:Normal
/sys/devices/system/memory/memory34/valid_zones:Normal
/sys/devices/system/memory/memory35/valid_zones:Normal
/sys/devices/system/memory/memory36/valid_zones:Normal
/sys/devices/system/memory/memory37/valid_zones:Normal
/sys/devices/system/memory/memory38/valid_zones:Normal
/sys/devices/system/memory/memory39/valid_zones:Normal Movable
Now
# echo online_movable > /sys/devices/system/memory/memory34/state
# grep . /sys/devices/system/memory/memory3?/valid_zones 2>/dev/null
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable
/sys/devices/system/memory/memory35/valid_zones:Movable
/sys/devices/system/memory/memory36/valid_zones:Movable
/sys/devices/system/memory/memory37/valid_zones:Movable
/sys/devices/system/memory/memory38/valid_zones:Movable
/sys/devices/system/memory/memory39/valid_zones:Movable
Block 33 can still be online both kernel and movable while all
the remaining can be only movable.
/proc/zonelist says
Node 0, zone Normal
pages free 0
min 0
low 0
high 0
spanned 0
present 0
--
Node 0, zone Movable
pages free 32753
min 85
low 117
high 149
spanned 32768
present 32768
A new memblock at a lower address will result in a new memblock (32)
which will still allow both Normal and Movable.
# sh probe_memblock.sh 0
# grep . /sys/devices/system/memory/memory3[2-5]/valid_zones 2>/dev/null
/sys/devices/system/memory/memory32/valid_zones:Normal Movable
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable
/sys/devices/system/memory/memory35/valid_zones:Movable
and online_kernel will convert it to the zone normal properly
while 33 can be still onlined both ways.
# echo online_kernel > /sys/devices/system/memory/memory32/state
# grep . /sys/devices/system/memory/memory3[2-5]/valid_zones 2>/dev/null
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable
/sys/devices/system/memory/memory35/valid_zones:Movable
/proc/zoneinfo will now tell
Node 0, zone Normal
pages free 65441
min 165
low 230
high 295
spanned 65536
present 65536
--
Node 0, zone Movable
pages free 32740
min 82
low 114
high 146
spanned 32768
present 32768
so both zones have one memblock spanned and present.
Onlining 39 should associate this block to the movable zone
# echo online > /sys/devices/system/memory/memory39/state
/proc/zoneinfo will now tell
Node 0, zone Normal
pages free 32765
min 80
low 112
high 144
spanned 32768
present 32768
--
Node 0, zone Movable
pages free 65501
min 160
low 225
high 290
spanned 196608
present 65536
so we will have a movable zone which spans 6 memblocks, 2 present and 4
representing a hole.
Offlining both movable blocks will lead to the zone with no present
pages which is the expected behavior I believe.
# echo offline > /sys/devices/system/memory/memory39/state
# echo offline > /sys/devices/system/memory/memory34/state
# grep -A6 "Movable\|Normal" /proc/zoneinfo
Node 0, zone Normal
pages free 32735
min 90
low 122
high 154
spanned 32768
present 32768
--
Node 0, zone Movable
pages free 0
min 0
low 0
high 0
spanned 196608
present 0
As a bonus we will get a nice cleanup in the memory hotplug codebase.
This patch (of 16):
init_currently_empty_zone doesn't have any error to return yet it is
still an int and callers try to be defensive and try to handle potential
error. Remove this nonsense and simplify all callers.
This patch shouldn't have any visible effect
Link: http://lkml.kernel.org/r/20170515085827.16474-2-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Tobias Regnery <tobias.regnery@gmail.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have seen an early OOM killer invocation on ppc64 systems with
crashkernel=4096M:
kthreadd invoked oom-killer: gfp_mask=0x16040c0(GFP_KERNEL|__GFP_COMP|__GFP_NOTRACK), nodemask=7, order=0, oom_score_adj=0
kthreadd cpuset=/ mems_allowed=7
CPU: 0 PID: 2 Comm: kthreadd Not tainted 4.4.68-1.gd7fe927-default #1
Call Trace:
dump_stack+0xb0/0xf0 (unreliable)
dump_header+0xb0/0x258
out_of_memory+0x5f0/0x640
__alloc_pages_nodemask+0xa8c/0xc80
kmem_getpages+0x84/0x1a0
fallback_alloc+0x2a4/0x320
kmem_cache_alloc_node+0xc0/0x2e0
copy_process.isra.25+0x260/0x1b30
_do_fork+0x94/0x470
kernel_thread+0x48/0x60
kthreadd+0x264/0x330
ret_from_kernel_thread+0x5c/0xa4
Mem-Info:
active_anon:0 inactive_anon:0 isolated_anon:0
active_file:0 inactive_file:0 isolated_file:0
unevictable:0 dirty:0 writeback:0 unstable:0
slab_reclaimable:5 slab_unreclaimable:73
mapped:0 shmem:0 pagetables:0 bounce:0
free:0 free_pcp:0 free_cma:0
Node 7 DMA free:0kB min:0kB low:0kB high:0kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:52428800kB managed:110016kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:320kB slab_unreclaimable:4672kB kernel_stack:1152kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
lowmem_reserve[]: 0 0 0 0
Node 7 DMA: 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB 0*8192kB 0*16384kB = 0kB
0 total pagecache pages
0 pages in swap cache
Swap cache stats: add 0, delete 0, find 0/0
Free swap = 0kB
Total swap = 0kB
819200 pages RAM
0 pages HighMem/MovableOnly
817481 pages reserved
0 pages cma reserved
0 pages hwpoisoned
the reason is that the managed memory is too low (only 110MB) while the
rest of the the 50GB is still waiting for the deferred intialization to
be done. update_defer_init estimates the initial memoty to initialize
to 2GB at least but it doesn't consider any memory allocated in that
range. In this particular case we've had
Reserving 4096MB of memory at 128MB for crashkernel (System RAM: 51200MB)
so the low 2GB is mostly depleted.
Fix this by considering memblock allocations in the initial static
initialization estimation. Move the max_initialise to
reset_deferred_meminit and implement a simple memblock_reserved_memory
helper which iterates all reserved blocks and sums the size of all that
start below the given address. The cumulative size is than added on top
of the initial estimation. This is still not ideal because
reset_deferred_meminit doesn't consider holes and so reservation might
be above the initial estimation whihch we ignore but let's make the
logic simpler until we really need to handle more complicated cases.
Fixes: 3a80a7fa79 ("mm: meminit: initialise a subset of struct pages if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set")
Link: http://lkml.kernel.org/r/20170531104010.GI27783@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> [4.2+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Roman Gushchin has reported that the OOM killer can trivially selects
next OOM victim when a thread doing memory allocation from page fault
path was selected as first OOM victim.
allocate invoked oom-killer: gfp_mask=0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null), order=0, oom_score_adj=0
allocate cpuset=/ mems_allowed=0
CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
Call Trace:
oom_kill_process+0x219/0x3e0
out_of_memory+0x11d/0x480
__alloc_pages_slowpath+0xc84/0xd40
__alloc_pages_nodemask+0x245/0x260
alloc_pages_vma+0xa2/0x270
__handle_mm_fault+0xca9/0x10c0
handle_mm_fault+0xf3/0x210
__do_page_fault+0x240/0x4e0
trace_do_page_fault+0x37/0xe0
do_async_page_fault+0x19/0x70
async_page_fault+0x28/0x30
...
Out of memory: Kill process 492 (allocate) score 899 or sacrifice child
Killed process 492 (allocate) total-vm:2052368kB, anon-rss:1894576kB, file-rss:4kB, shmem-rss:0kB
allocate: page allocation failure: order:0, mode:0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null)
allocate cpuset=/ mems_allowed=0
CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
Call Trace:
__alloc_pages_slowpath+0xd32/0xd40
__alloc_pages_nodemask+0x245/0x260
alloc_pages_vma+0xa2/0x270
__handle_mm_fault+0xca9/0x10c0
handle_mm_fault+0xf3/0x210
__do_page_fault+0x240/0x4e0
trace_do_page_fault+0x37/0xe0
do_async_page_fault+0x19/0x70
async_page_fault+0x28/0x30
...
oom_reaper: reaped process 492 (allocate), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
...
allocate invoked oom-killer: gfp_mask=0x0(), nodemask=(null), order=0, oom_score_adj=0
allocate cpuset=/ mems_allowed=0
CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
Call Trace:
oom_kill_process+0x219/0x3e0
out_of_memory+0x11d/0x480
pagefault_out_of_memory+0x68/0x80
mm_fault_error+0x8f/0x190
? handle_mm_fault+0xf3/0x210
__do_page_fault+0x4b2/0x4e0
trace_do_page_fault+0x37/0xe0
do_async_page_fault+0x19/0x70
async_page_fault+0x28/0x30
...
Out of memory: Kill process 233 (firewalld) score 10 or sacrifice child
Killed process 233 (firewalld) total-vm:246076kB, anon-rss:20956kB, file-rss:0kB, shmem-rss:0kB
There is a race window that the OOM reaper completes reclaiming the
first victim's memory while nothing but mutex_trylock() prevents the
first victim from calling out_of_memory() from pagefault_out_of_memory()
after memory allocation for page fault path failed due to being selected
as an OOM victim.
This is a side effect of commit 9a67f6488e ("mm: consolidate
GFP_NOFAIL checks in the allocator slowpath") because that commit
silently changed the behavior from
/* Avoid allocations with no watermarks from looping endlessly */
to
/*
* Give up allocations without trying memory reserves if selected
* as an OOM victim
*/
in __alloc_pages_slowpath() by moving the location to check TIF_MEMDIE
flag. I have noticed this change but I didn't post a patch because I
thought it is an acceptable change other than noise by warn_alloc()
because !__GFP_NOFAIL allocations are allowed to fail. But we
overlooked that failing memory allocation from page fault path makes
difference due to the race window explained above.
While it might be possible to add a check to pagefault_out_of_memory()
that prevents the first victim from calling out_of_memory() or remove
out_of_memory() from pagefault_out_of_memory(), changing
pagefault_out_of_memory() does not suppress noise by warn_alloc() when
allocating thread was selected as an OOM victim. There is little point
with printing similar backtraces and memory information from both
out_of_memory() and warn_alloc().
Instead, if we guarantee that current thread can try allocations with no
watermarks once when current thread looping inside
__alloc_pages_slowpath() was selected as an OOM victim, we can follow "who
can use memory reserves" rules and suppress noise by warn_alloc() and
prevent memory allocations from page fault path from calling
pagefault_out_of_memory().
If we take the comment literally, this patch would do
- if (test_thread_flag(TIF_MEMDIE))
- goto nopage;
+ if (alloc_flags == ALLOC_NO_WATERMARKS || (gfp_mask & __GFP_NOMEMALLOC))
+ goto nopage;
because gfp_pfmemalloc_allowed() returns false if __GFP_NOMEMALLOC is
given. But if I recall correctly (I couldn't find the message), the
condition is meant to apply to only OOM victims despite the comment.
Therefore, this patch preserves TIF_MEMDIE check.
Fixes: 9a67f6488e ("mm: consolidate GFP_NOFAIL checks in the allocator slowpath")
Link: http://lkml.kernel.org/r/201705192112.IAF69238.OQOHSJLFOFFMtV@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: Roman Gushchin <guro@fb.com>
Tested-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: <stable@vger.kernel.org> [4.11]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The previous patch ("mm: prevent potential recursive reclaim due to
clearing PF_MEMALLOC") has shown that simply setting and clearing
PF_MEMALLOC in current->flags can result in wrongly clearing a
pre-existing PF_MEMALLOC flag and potentially lead to recursive reclaim.
Let's introduce helpers that support proper nesting by saving the
previous stat of the flag, similar to the existing memalloc_noio_* and
memalloc_nofs_* helpers. Convert existing setting/clearing of
PF_MEMALLOC within mm to the new helpers.
There are no known issues with the converted code, but the change makes
it more robust.
Link: http://lkml.kernel.org/r/20170405074700.29871-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Chris Leech <cleech@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Lee Duncan <lduncan@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "more robust PF_MEMALLOC handling"
This series aims to unify the setting and clearing of PF_MEMALLOC, which
prevents recursive reclaim. There are some places that clear the flag
unconditionally from current->flags, which may result in clearing a
pre-existing flag. This already resulted in a bug report that Patch 1
fixes (without the new helpers, to make backporting easier). Patch 2
introduces the new helpers, modelled after existing memalloc_noio_* and
memalloc_nofs_* helpers, and converts mm core to use them. Patches 3
and 4 convert non-mm code.
This patch (of 4):
__alloc_pages_direct_compact() sets PF_MEMALLOC to prevent deadlock
during page migration by lock_page() (see the comment in
__unmap_and_move()). Then it unconditionally clears the flag, which can
clear a pre-existing PF_MEMALLOC flag and result in recursive reclaim.
This was not a problem until commit a8161d1ed6 ("mm, page_alloc:
restructure direct compaction handling in slowpath"), because direct
compation was called only after direct reclaim, which was skipped when
PF_MEMALLOC flag was set.
Even now it's only a theoretical issue, as the new callsite of
__alloc_pages_direct_compact() is reached only for costly orders and
when gfp_pfmemalloc_allowed() is true, which means either
__GFP_NOMEMALLOC is in gfp_flags or in_interrupt() is true. There is no
such known context, but let's play it safe and make
__alloc_pages_direct_compact() robust for cases where PF_MEMALLOC is
already set.
Fixes: a8161d1ed6 ("mm, page_alloc: restructure direct compaction handling in slowpath")
Link: http://lkml.kernel.org/r/20170405074700.29871-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Chris Leech <cleech@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Lee Duncan <lduncan@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The migrate scanner in async compaction is currently limited to
MIGRATE_MOVABLE pageblocks. This is a heuristic intended to reduce
latency, based on the assumption that non-MOVABLE pageblocks are
unlikely to contain movable pages.
However, with the exception of THP's, most high-order allocations are
not movable. Should the async compaction succeed, this increases the
chance that the non-MOVABLE allocations will fallback to a MOVABLE
pageblock, making the long-term fragmentation worse.
This patch attempts to help the situation by changing async direct
compaction so that the migrate scanner only scans the pageblocks of the
requested migratetype. If it's a non-MOVABLE type and there are such
pageblocks that do contain movable pages, chances are that the
allocation can succeed within one of such pageblocks, removing the need
for a fallback. If that fails, the subsequent sync attempt will ignore
this restriction.
In testing based on 4.9 kernel with stress-highalloc from mmtests
configured for order-4 GFP_KERNEL allocations, this patch has reduced
the number of unmovable allocations falling back to movable pageblocks
by 30%. The number of movable allocations falling back is reduced by
12%.
Link: http://lkml.kernel.org/r/20170307131545.28577-8-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When stealing pages from pageblock of a different migratetype, we count
how many free pages were stolen, and change the pageblock's migratetype
if more than half of the pageblock was free. This might be too
conservative, as there might be other pages that are not free, but were
allocated with the same migratetype as our allocation requested.
While we cannot determine the migratetype of allocated pages precisely
(at least without the page_owner functionality enabled), we can count
pages that compaction would try to isolate for migration - those are
either on LRU or __PageMovable(). The rest can be assumed to be
MIGRATE_RECLAIMABLE or MIGRATE_UNMOVABLE, which we cannot easily
distinguish. This counting can be done as part of free page stealing
with little additional overhead.
The page stealing code is changed so that it considers free pages plus
pages of the "good" migratetype for the decision whether to change
pageblock's migratetype.
The result should be more accurate migratetype of pageblocks wrt the
actual pages in the pageblocks, when stealing from semi-occupied
pageblocks. This should help the efficiency of page grouping by
mobility.
In testing based on 4.9 kernel with stress-highalloc from mmtests
configured for order-4 GFP_KERNEL allocations, this patch has reduced
the number of unmovable allocations falling back to movable pageblocks
by 47%. The number of movable allocations falling back to other
pageblocks are increased by 55%, but these events don't cause permanent
fragmentation, so the tradeoff should be positive. Later patches also
offset the movable fallback increase to some extent.
[akpm@linux-foundation.org: merge fix]
Link: http://lkml.kernel.org/r/20170307131545.28577-5-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The __rmqueue_fallback() function is called when there's no free page of
requested migratetype, and we need to steal from a different one.
There are various heuristics to make this event infrequent and reduce
permanent fragmentation. The main one is to try stealing from a
pageblock that has the most free pages, and possibly steal them all at
once and convert the whole pageblock. Precise searching for such
pageblock would be expensive, so instead the heuristics walks the free
lists from MAX_ORDER down to requested order and assumes that the block
with highest-order free page is likely to also have the most free pages
in total.
Chances are that together with the highest-order page, we steal also
pages of lower orders from the same block. But then we still split the
highest order page. This is wasteful and can contribute to
fragmentation instead of avoiding it.
This patch thus changes __rmqueue_fallback() to just steal the page(s)
and put them on the freelist of the requested migratetype, and only
report whether it was successful. Then we pick (and eventually split)
the smallest page with __rmqueue_smallest(). This all happens under
zone lock, so nobody can steal it from us in the process. This should
reduce fragmentation due to fallbacks. At worst we are only stealing a
single highest-order page and waste some cycles by moving it between
lists and then removing it, but fallback is not exactly hot path so that
should not be a concern. As a side benefit the patch removes some
duplicate code by reusing __rmqueue_smallest().
[vbabka@suse.cz: fix endless loop in the modified __rmqueue()]
Link: http://lkml.kernel.org/r/59d71b35-d556-4fc9-ee2e-1574259282fd@suse.cz
Link: http://lkml.kernel.org/r/20170307131545.28577-4-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
o Pretty much a full rewrite of the processing of function plugins.
i.e. echo do_IRQ:stacktrace > set_ftrace_filter
o The rewrite was needed to add plugins to be unique to tracing instances.
i.e. mkdir instance/foo; cd instances/foo; echo do_IRQ:stacktrace > set_ftrace_filter
The old way was written very hacky. This removes a lot of those hacks.
o New "function-fork" tracing option. When set, pids in the set_ftrace_pid
will have their children added when the processes with their pids
listed in the set_ftrace_pid file forks.
o Exposure of "maxactive" for kretprobe in kprobe_events
o Allow for builtin init functions to be traced by the function tracer
(via the kernel command line). Module init function tracing will come
in the next release.
o Added more selftests, and have selftests also test in an instance.
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Merge tag 'trace-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
"New features for this release:
- Pretty much a full rewrite of the processing of function plugins.
i.e. echo do_IRQ:stacktrace > set_ftrace_filter
- The rewrite was needed to add plugins to be unique to tracing
instances. i.e. mkdir instance/foo; cd instances/foo; echo
do_IRQ:stacktrace > set_ftrace_filter The old way was written very
hacky. This removes a lot of those hacks.
- New "function-fork" tracing option. When set, pids in the
set_ftrace_pid will have their children added when the processes
with their pids listed in the set_ftrace_pid file forks.
- Exposure of "maxactive" for kretprobe in kprobe_events
- Allow for builtin init functions to be traced by the function
tracer (via the kernel command line). Module init function tracing
will come in the next release.
- Added more selftests, and have selftests also test in an instance"
* tag 'trace-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (60 commits)
ring-buffer: Return reader page back into existing ring buffer
selftests: ftrace: Allow some event trigger tests to run in an instance
selftests: ftrace: Have some basic tests run in a tracing instance too
selftests: ftrace: Have event tests also run in an tracing instance
selftests: ftrace: Make func_event_triggers and func_traceonoff_triggers tests do instances
selftests: ftrace: Allow some tests to be run in a tracing instance
tracing/ftrace: Allow for instances to trigger their own stacktrace probes
tracing/ftrace: Allow for the traceonoff probe be unique to instances
tracing/ftrace: Enable snapshot function trigger to work with instances
tracing/ftrace: Allow instances to have their own function probes
tracing/ftrace: Add a better way to pass data via the probe functions
ftrace: Dynamically create the probe ftrace_ops for the trace_array
tracing: Pass the trace_array into ftrace_probe_ops functions
tracing: Have the trace_array hold the list of registered func probes
ftrace: If the hash for a probe fails to update then free what was initialized
ftrace: Have the function probes call their own function
ftrace: Have each function probe use its own ftrace_ops
ftrace: Have unregister_ftrace_function_probe_func() return a value
ftrace: Add helper function ftrace_hash_move_and_update_ops()
ftrace: Remove data field from ftrace_func_probe structure
...
Commit c0a32fc5a2 ("mm: more intensive memory corruption debugging")
changed to check debug_guardpage_minorder() > 0 when reporting
allocation failures. The reasoning was
When we use guard page to debug memory corruption, it shrinks
available pages to 1/2, 1/4, 1/8 and so on, depending on parameter
value. In such case memory allocation failures can be common and
printing errors can flood dmesg. If somebody debug corruption,
allocation failures are not the things he/she is interested about.
but this is misguided.
Allocation requests with __GFP_NOWARN flag by definition do not cause
flooding of allocation failure messages. Allocation requests with
__GFP_NORETRY flag likely also have __GFP_NOWARN flag. Costly
allocation requests likely also have __GFP_NOWARN flag.
Allocation requests without __GFP_DIRECT_RECLAIM flag likely also have
__GFP_NOWARN flag or __GFP_HIGH flag. Non-costly allocation requests
with __GFP_DIRECT_RECLAIM flag basically retry forever due to the "too
small to fail" memory-allocation rule.
Therefore, as a whole, shrinking available pages by
debug_guardpage_minorder= kernel boot parameter might cause flooding of
OOM killer messages but unlikely causes flooding of allocation failure
messages. Let's remove debug_guardpage_minorder() > 0 check which would
likely be pointless.
Link: http://lkml.kernel.org/r/1491910035-4231-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On SPARSEMEM systems page poisoning is enabled after buddy is up,
because of the dependency on page extension init. This causes the pages
released by free_all_bootmem not to be poisoned. This either delays or
misses the identification of some issues because the pages have to
undergo another cycle of alloc-free-alloc for any corruption to be
detected.
Enable page poisoning early by getting rid of the PAGE_EXT_DEBUG_POISON
flag. Since all the free pages will now be poisoned, the flag need not
be verified before checking the poison during an alloc.
[vinmenon@codeaurora.org: fix Kconfig]
Link: http://lkml.kernel.org/r/1490878002-14423-1-git-send-email-vinmenon@codeaurora.org
Link: http://lkml.kernel.org/r/1490358246-11001-1-git-send-email-vinmenon@codeaurora.org
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Acked-by: Laura Abbott <labbott@redhat.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__GFP_NOWARN, which is usually added to avoid warnings from callsites
that expect to fail and have fallbacks, currently also suppresses
allocation stall warnings. These trigger when an allocation is stuck
inside the allocator for 10 seconds or longer.
But there is no class of allocations that can get legitimately stuck in
the allocator for this long. This always indicates a problem.
Always emit stall warnings. Restrict __GFP_NOWARN to alloc failures.
Link: http://lkml.kernel.org/r/20170125181150.GA16398@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
GFP_NOFS context is used for the following 5 reasons currently:
- to prevent from deadlocks when the lock held by the allocation
context would be needed during the memory reclaim
- to prevent from stack overflows during the reclaim because the
allocation is performed from a deep context already
- to prevent lockups when the allocation context depends on other
reclaimers to make a forward progress indirectly
- just in case because this would be safe from the fs POV
- silence lockdep false positives
Unfortunately overuse of this allocation context brings some problems to
the MM. Memory reclaim is much weaker (especially during heavy FS
metadata workloads), OOM killer cannot be invoked because the MM layer
doesn't have enough information about how much memory is freeable by the
FS layer.
In many cases it is far from clear why the weaker context is even used
and so it might be used unnecessarily. We would like to get rid of
those as much as possible. One way to do that is to use the flag in
scopes rather than isolated cases. Such a scope is declared when really
necessary, tracked per task and all the allocation requests from within
the context will simply inherit the GFP_NOFS semantic.
Not only this is easier to understand and maintain because there are
much less problematic contexts than specific allocation requests, this
also helps code paths where FS layer interacts with other layers (e.g.
crypto, security modules, MM etc...) and there is no easy way to convey
the allocation context between the layers.
Introduce memalloc_nofs_{save,restore} API to control the scope of
GFP_NOFS allocation context. This is basically copying
memalloc_noio_{save,restore} API we have for other restricted allocation
context GFP_NOIO. The PF_MEMALLOC_NOFS flag already exists and it is
just an alias for PF_FSTRANS which has been xfs specific until recently.
There are no more PF_FSTRANS users anymore so let's just drop it.
PF_MEMALLOC_NOFS is now checked in the MM layer and drops __GFP_FS
implicitly same as PF_MEMALLOC_NOIO drops __GFP_IO. memalloc_noio_flags
is renamed to current_gfp_context because it now cares about both
PF_MEMALLOC_NOFS and PF_MEMALLOC_NOIO contexts. Xfs code paths preserve
their semantic. kmem_flags_convert() doesn't need to evaluate the flag
anymore.
This patch shouldn't introduce any functional changes.
Let's hope that filesystems will drop direct GFP_NOFS (resp. ~__GFP_FS)
usage as much as possible and only use a properly documented
memalloc_nofs_{save,restore} checkpoints where they are appropriate.
[akpm@linux-foundation.org: fix comment typo, reflow comment]
Link: http://lkml.kernel.org/r/20170306131408.9828-5-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Nikolay Borisov <nborisov@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Introduce two helpers, is_migrate_highatomic() and is_migrate_highatomic_page().
Simplify the code, no functional changes.
[akpm@linux-foundation.org: use static inlines rather than macros, per mhocko]
Link: http://lkml.kernel.org/r/58B94F15.6060606@huawei.com
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The backoff mechanism is not needed. If we have MAX_RECLAIM_RETRIES
loops without progress, we'll OOM anyway; backing off might cut one or
two iterations off that in the rare OOM case. If we have intermittent
success reclaiming a few pages, the backoff function gets reset also,
and so is of little help in these scenarios.
We might want a backoff function for when there IS progress, but not
enough to be satisfactory. But this isn't that. Remove it.
Link: http://lkml.kernel.org/r/20170228214007.5621-10-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jia He <hejianet@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
NR_PAGES_SCANNED counts number of pages scanned since the last page free
event in the allocator. This was used primarily to measure the
reclaimability of zones and nodes, and determine when reclaim should
give up on them. In that role, it has been replaced in the preceding
patches by a different mechanism.
Being implemented as an efficient vmstat counter, it was automatically
exported to userspace as well. It's however unlikely that anyone
outside the kernel is using this counter in any meaningful way.
Remove the counter and the unused pgdat_reclaimable().
Link: http://lkml.kernel.org/r/20170228214007.5621-8-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jia He <hejianet@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm: kswapd spinning on unreclaimable nodes - fixes and
cleanups".
Jia reported a scenario in which the kswapd of a node indefinitely spins
at 100% CPU usage. We have seen similar cases at Facebook.
The kernel's current method of judging its ability to reclaim a node (or
whether to back off and sleep) is based on the amount of scanned pages
in proportion to the amount of reclaimable pages. In Jia's and our
scenarios, there are no reclaimable pages in the node, however, and the
condition for backing off is never met. Kswapd busyloops in an attempt
to restore the watermarks while having nothing to work with.
This series reworks the definition of an unreclaimable node based not on
scanning but on whether kswapd is able to actually reclaim pages in
MAX_RECLAIM_RETRIES (16) consecutive runs. This is the same criteria
the page allocator uses for giving up on direct reclaim and invoking the
OOM killer. If it cannot free any pages, kswapd will go to sleep and
leave further attempts to direct reclaim invocations, which will either
make progress and re-enable kswapd, or invoke the OOM killer.
Patch #1 fixes the immediate problem Jia reported, the remainder are
smaller fixlets, cleanups, and overall phasing out of the old method.
Patch #6 is the odd one out. It's a nice cleanup to get_scan_count(),
and directly related to #5, but in itself not relevant to the series.
If the whole series is too ambitious for 4.11, I would consider the
first three patches fixes, the rest cleanups.
This patch (of 9):
Jia He reports a problem with kswapd spinning at 100% CPU when
requesting more hugepages than memory available in the system:
$ echo 4000 >/proc/sys/vm/nr_hugepages
top - 13:42:59 up 3:37, 1 user, load average: 1.09, 1.03, 1.01
Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.0 us, 12.5 sy, 0.0 ni, 85.5 id, 2.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem: 31371520 total, 30915136 used, 456384 free, 320 buffers
KiB Swap: 6284224 total, 115712 used, 6168512 free. 48192 cached Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
76 root 20 0 0 0 0 R 100.0 0.000 217:17.29 kswapd3
At that time, there are no reclaimable pages left in the node, but as
kswapd fails to restore the high watermarks it refuses to go to sleep.
Kswapd needs to back away from nodes that fail to balance. Up until
commit 1d82de618d ("mm, vmscan: make kswapd reclaim in terms of
nodes") kswapd had such a mechanism. It considered zones whose
theoretically reclaimable pages it had reclaimed six times over as
unreclaimable and backed away from them. This guard was erroneously
removed as the patch changed the definition of a balanced node.
However, simply restoring this code wouldn't help in the case reported
here: there *are* no reclaimable pages that could be scanned until the
threshold is met. Kswapd would stay awake anyway.
Introduce a new and much simpler way of backing off. If kswapd runs
through MAX_RECLAIM_RETRIES (16) cycles without reclaiming a single
page, make it back off from the node. This is the same number of shots
direct reclaim takes before declaring OOM. Kswapd will go to sleep on
that node until a direct reclaimer manages to reclaim some pages, thus
proving the node reclaimable again.
[hannes@cmpxchg.org: check kswapd failure against the cumulative nr_reclaimed count]
Link: http://lkml.kernel.org/r/20170306162410.GB2090@cmpxchg.org
[shakeelb@google.com: fix condition for throttle_direct_reclaim]
Link: http://lkml.kernel.org/r/20170314183228.20152-1-shakeelb@google.com
Link: http://lkml.kernel.org/r/20170228214007.5621-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reported-by: Jia He <hejianet@gmail.com>
Tested-by: Jia He <hejianet@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
guide for user-space API documents, rather sparsely populated at the
moment, but it's a start. Markus improved the infrastructure for
converting diagrams. Mauro has converted much of the USB documentation
over to RST. Plus the usual set of fixes, improvements, and tweaks.
There's a bit more than the usual amount of reaching out of Documentation/
to fix comments elsewhere in the tree; I have acks for those where I could
get them.
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Merge tag 'docs-4.12' of git://git.lwn.net/linux
Pull documentation update from Jonathan Corbet:
"A reasonably busy cycle for documentation this time around. There is a
new guide for user-space API documents, rather sparsely populated at
the moment, but it's a start. Markus improved the infrastructure for
converting diagrams. Mauro has converted much of the USB documentation
over to RST. Plus the usual set of fixes, improvements, and tweaks.
There's a bit more than the usual amount of reaching out of
Documentation/ to fix comments elsewhere in the tree; I have acks for
those where I could get them"
* tag 'docs-4.12' of git://git.lwn.net/linux: (74 commits)
docs: Fix a couple typos
docs: Fix a spelling error in vfio-mediated-device.txt
docs: Fix a spelling error in ioctl-number.txt
MAINTAINERS: update file entry for HSI subsystem
Documentation: allow installing man pages to a user defined directory
Doc/PM: Sync with intel_powerclamp code behavior
zr364xx.rst: usb/devices is now at /sys/kernel/debug/
usb.rst: move documentation from proc_usb_info.txt to USB ReST book
convert philips.txt to ReST and add to media docs
docs-rst: usb: update old usbfs-related documentation
arm: Documentation: update a path name
docs: process/4.Coding.rst: Fix a couple of document refs
docs-rst: fix usb cross-references
usb: gadget.h: be consistent at kernel doc macros
usb: composite.h: fix two warnings when building docs
usb: get rid of some ReST doc build errors
usb.rst: get rid of some Sphinx errors
usb/URB.txt: convert to ReST and update it
usb/persist.txt: convert to ReST and add to driver-api book
usb/hotplug.txt: convert to ReST and add to driver-api book
...
This reverts commit 374ad05ab6.
While the patch worked great for userspace allocations, the fact that
softirq loses the per-cpu allocator caused problems. It needs to be
redone taking into account that a separate list is needed for hard/soft
IRQs or alternatively find a cheap way of detecting reentry due to an
interrupt. Both are possible but sufficiently tricky that it shouldn't
be rushed.
Jesper had one method for allowing softirqs but reported that the cost
was high enough that it performed similarly to a plain revert. His
figures for netperf TCP_STREAM were as follows
Baseline v4.10.0 : 60316 Mbit/s
Current 4.11.0-rc6: 47491 Mbit/s
Jesper's patch : 60662 Mbit/s
This patch : 60106 Mbit/s
As this is a regression, I wish to revert to noirq allocator for now and
go back to the drawing board.
Link: http://lkml.kernel.org/r/20170415145350.ixy7vtrzdzve57mh@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Tariq Toukan <ttoukan.linux@gmail.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We currently have 2 specific WQ_RECLAIM workqueues in the mm code.
vmstat_wq for updating pcp stats and lru_add_drain_wq dedicated to drain
per cpu lru caches. This seems more than necessary because both can run
on a single WQ. Both do not block on locks requiring a memory
allocation nor perform any allocations themselves. We will save one
rescuer thread this way.
On the other hand drain_all_pages() queues work on the system wq which
doesn't have rescuer and so this depend on memory allocation (when all
workers are stuck allocating and new ones cannot be created).
Initially we thought this would be more of a theoretical problem but
Hugh Dickins has reported:
: 4.11-rc has been giving me hangs after hours of swapping load. At
: first they looked like memory leaks ("fork: Cannot allocate memory");
: but for no good reason I happened to do "cat /proc/sys/vm/stat_refresh"
: before looking at /proc/meminfo one time, and the stat_refresh stuck
: in D state, waiting for completion of flush_work like many kworkers.
: kthreadd waiting for completion of flush_work in drain_all_pages().
This worker should be using WQ_RECLAIM as well in order to guarantee a
forward progress. We can reuse the same one as for lru draining and
vmstat.
Link: http://lkml.kernel.org/r/20170307131751.24936-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Tested-by: Yang Li <pku.leo@gmail.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Relying on free_reserved_area() to call ftrace to free init memory proved to
not be sufficient. The issue is that on x86, when debug_pagealloc is
enabled, the init memory is not freed, but simply set as not present. Since
ftrace was uninformed of this, starting function tracing still tries to
update pages that are not present according to the page tables, causing
ftrace to bug, as well as killing the kernel itself.
Instead of relying on free_reserved_area(), have init/main.c call ftrace
directly just before it frees the init memory. Then it needs to use
__init_begin and __init_end to know where the init memory location is.
Looking at all archs (and testing what I can), it appears that this should
work for each of them.
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Adding a hook into free_reserve_area() that informs ftrace that boot up init
text is being free, lets ftrace safely remove those init functions from its
records, which keeps ftrace from trying to modify text that no longer
exists.
Note, this still does not allow for tracing .init text of modules, as
modules require different work for freeing its init code.
Link: http://lkml.kernel.org/r/1488502497.7212.24.camel@linux.intel.com
Cc: linux-mm@kvack.org
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Requested-by: Todd Brandt <todd.e.brandt@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Commit 13ad59df67 ("mm, page_alloc: avoid page_to_pfn() when merging
buddies") moved the check for memory holes out of page_is_buddy() and
had the callers do the check.
But this wasn't done correctly in one place which caused ia64 to crash
very early in boot.
Update to fix that and make ia64 boot again.
[ v2: Vlastimil pointed out we don't need to call page_to_pfn()
since we already have the result of that in "buddy_pfn" ]
Fixes: 13ad59df67 ("avoid page_to_pfn() when merging buddies")
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Update the .c files that depend on these APIs.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fix typos and add the following to the scripts/spelling.txt:
algined||aligned
While we are here, fix the "appplication" in the touched line in
drivers/block/loop.c. Also, fix the "may not naturally ..." to
"may not be naturally ..." in the touched line in mm/page_alloc.
Link: http://lkml.kernel.org/r/1481573103-11329-9-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
arch_zone_lowest/highest_possible_pfn[] is set to 0 and [ZONE_MOVABLE]
is skipped in the loop. No need to reset them to 0 again.
This patch just removes the redundant code.
Link: http://lkml.kernel.org/r/20170209141731.60208-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When @node_reclaim_node isn't 0, the page allocator tries to reclaim
pages if the amount of free memory in the zones are below the low
watermark. On Power platform, none of NUMA nodes are scanned for page
reclaim because no nodes match the condition in zone_allows_reclaim().
On Power platform, RECLAIM_DISTANCE is set to 10 which is the distance
of Node-A to Node-A. So the preferred node even won't be scanned for
page reclaim.
__alloc_pages_nodemask()
get_page_from_freelist()
zone_allows_reclaim()
Anton proposed the test code as below:
# cat alloc.c
:
int main(int argc, char *argv[])
{
void *p;
unsigned long size;
unsigned long start, end;
start = time(NULL);
size = strtoul(argv[1], NULL, 0);
printf("To allocate %ldGB memory\n", size);
size <<= 30;
p = malloc(size);
assert(p);
memset(p, 0, size);
end = time(NULL);
printf("Used time: %ld seconds\n", end - start);
sleep(3600);
return 0;
}
The system I use for testing has two NUMA nodes. Both have 128GB
memory. In below scnario, the page caches on node#0 should be reclaimed
when it encounters pressure to accommodate request of allocation.
# echo 2 > /proc/sys/vm/zone_reclaim_mode; \
sync; \
echo 3 > /proc/sys/vm/drop_caches; \
# taskset -c 0 cat file.32G > /dev/null; \
grep FilePages /sys/devices/system/node/node0/meminfo
Node 0 FilePages: 33619712 kB
# taskset -c 0 ./alloc 128
# grep FilePages /sys/devices/system/node/node0/meminfo
Node 0 FilePages: 33619840 kB
# grep MemFree /sys/devices/system/node/node0/meminfo
Node 0 MemFree: 186816 kB
With the patch applied, the pagecache on node-0 is reclaimed when its
free memory is running out. It's the expected behaviour.
# echo 2 > /proc/sys/vm/zone_reclaim_mode; \
sync; \
echo 3 > /proc/sys/vm/drop_caches
# taskset -c 0 cat file.32G > /dev/null; \
grep FilePages /sys/devices/system/node/node0/meminfo
Node 0 FilePages: 33605568 kB
# taskset -c 0 ./alloc 128
# grep FilePages /sys/devices/system/node/node0/meminfo
Node 0 FilePages: 1379520 kB
# grep MemFree /sys/devices/system/node/node0/meminfo
Node 0 MemFree: 317120 kB
Fixes: 5f7a75acdb ("mm: page_alloc: do not cache reclaim distances")
Link: http://lkml.kernel.org/r/1486532455-29613-1-git-send-email-gwshan@linux.vnet.ibm.com
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: <stable@vger.kernel.org> [3.16+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently alloc_contig_range assumes that the compaction should be done
with the default GFP_KERNEL flags. This is probably right for all
current uses of this interface, but may change as CMA is used in more
use-cases (including being the default DMA memory allocator on some
platforms).
Change the function prototype, to allow for passing through the GFP mask
set by upper layers.
Also respect global restrictions by applying memalloc_noio_flags to the
passed in flags.
Link: http://lkml.kernel.org/r/20170127172328.18574-1-l.stach@pengutronix.de
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alexander Graf <agraf@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We had considered all of the non-lru pages as unmovable before commit
bda807d444 ("mm: migrate: support non-lru movable page migration").
But now some of non-lru pages like zsmalloc, virtio-balloon pages also
become movable. So we can offline such blocks by using non-lru page
migration.
This patch straightforwardly adds non-lru migration code, which means
adding non-lru related code to the functions which scan over pfn and
collect pages to be migrated and isolate them before migration.
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As suggested by Vlastimil Babka and Tejun Heo, this patch uses a static
work_struct to co-ordinate the draining of per-cpu pages on the
workqueue. Only one task can drain at a time but this is better than
the previous scheme that allowed multiple tasks to send IPIs at a time.
One consideration is whether parallel requests should synchronise
against each other. This patch does not synchronise for a global drain
as the common case for such callers is expected to be multiple parallel
direct reclaimers competing for pages when the watermark is close to
min. Draining the per-cpu list is unlikely to make much progress and
serialising the drain is of dubious merit. Drains are synchonrised for
callers such as memory hotplug and CMA that care about the drain being
complete when the function returns.
Link: http://lkml.kernel.org/r/20170125083038.rzb5f43nptmk7aed@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Suggested-by: Tejun Heo <tj@kernel.org>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 682a3385e7 ("mm, page_alloc: inline the fast path of the
zonelist iterator") we replace a NULL nodemask with
cpuset_current_mems_allowed in the fast path, so that
get_page_from_freelist() filters nodes allowed by the cpuset via
for_next_zone_zonelist_nodemask().
In that case it's pointless to additionaly check __cpuset_zone_allowed()
in each iteration, which we can avoid by not adding ALLOC_CPUSET to
alloc_flags in that scenario.
This saves some cycles in the allocator fast path on systems with one or
more non-root cpuset configured. In the slow path, ALLOC_CPUSET is
reset according to __alloc_pages_slowpath(). Without configured
cpusets, this code is disabled by a static key.
Link: http://lkml.kernel.org/r/20170124150511.5710-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The allocation fast path contains two similar checks for zoneref->zone
being NULL, where zoneref points either to the first zone in the
zonelist, or to the preferred zone. These can be NULL either due to
empty zonelist, or no zone being compatible with given nodemask or
task's cpuset.
These checks are unnecessary, because the zonelist walks in
first_zones_zonelist() and get_page_from_freelist() handle a NULL
starting zoneref->zone or preferred_zoneref->zone safely. It's safe to
fallback to __alloc_pages_slowpath() where we also have the check early
enough.
Link: http://lkml.kernel.org/r/20170124150511.5710-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Many workloads that allocate pages are not handling an interrupt at a
time. As allocation requests may be from IRQ context, it's necessary to
disable/enable IRQs for every page allocation. This cost is the bulk of
the free path but also a significant percentage of the allocation path.
This patch alters the locking and checks such that only irq-safe
allocation requests use the per-cpu allocator. All others acquire the
irq-safe zone->lock and allocate from the buddy allocator. It relies on
disabling preemption to safely access the per-cpu structures. It could
be slightly modified to avoid soft IRQs using it but it's not clear it's
worthwhile.
This modification may slow allocations from IRQ context slightly but the
main gain from the per-cpu allocator is that it scales better for
allocations from multiple contexts. There is an implicit assumption
that intensive allocations from IRQ contexts on multiple CPUs from a
single NUMA node are rare and that the fast majority of scaling issues
are encountered in !IRQ contexts such as page faulting. It's worth
noting that this patch is not required for a bulk page allocator but it
significantly reduces the overhead.
The following is results from a page allocator micro-benchmark. Only
order-0 is interesting as higher orders do not use the per-cpu allocator
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Amean alloc-odr0-1 287.15 ( 0.00%) 219.00 ( 23.73%)
Amean alloc-odr0-2 221.23 ( 0.00%) 183.23 ( 17.18%)
Amean alloc-odr0-4 187.00 ( 0.00%) 151.38 ( 19.05%)
Amean alloc-odr0-8 167.54 ( 0.00%) 132.77 ( 20.75%)
Amean alloc-odr0-16 156.00 ( 0.00%) 123.00 ( 21.15%)
Amean alloc-odr0-32 149.00 ( 0.00%) 118.31 ( 20.60%)
Amean alloc-odr0-64 138.77 ( 0.00%) 116.00 ( 16.41%)
Amean alloc-odr0-128 145.00 ( 0.00%) 118.00 ( 18.62%)
Amean alloc-odr0-256 136.15 ( 0.00%) 125.00 ( 8.19%)
Amean alloc-odr0-512 147.92 ( 0.00%) 121.77 ( 17.68%)
Amean alloc-odr0-1024 147.23 ( 0.00%) 126.15 ( 14.32%)
Amean alloc-odr0-2048 155.15 ( 0.00%) 129.92 ( 16.26%)
Amean alloc-odr0-4096 164.00 ( 0.00%) 136.77 ( 16.60%)
Amean alloc-odr0-8192 166.92 ( 0.00%) 138.08 ( 17.28%)
Amean alloc-odr0-16384 159.00 ( 0.00%) 138.00 ( 13.21%)
Amean free-odr0-1 165.00 ( 0.00%) 89.00 ( 46.06%)
Amean free-odr0-2 113.00 ( 0.00%) 63.00 ( 44.25%)
Amean free-odr0-4 99.00 ( 0.00%) 54.00 ( 45.45%)
Amean free-odr0-8 88.00 ( 0.00%) 47.38 ( 46.15%)
Amean free-odr0-16 83.00 ( 0.00%) 46.00 ( 44.58%)
Amean free-odr0-32 80.00 ( 0.00%) 44.38 ( 44.52%)
Amean free-odr0-64 72.62 ( 0.00%) 43.00 ( 40.78%)
Amean free-odr0-128 78.00 ( 0.00%) 42.00 ( 46.15%)
Amean free-odr0-256 80.46 ( 0.00%) 57.00 ( 29.16%)
Amean free-odr0-512 96.38 ( 0.00%) 64.69 ( 32.88%)
Amean free-odr0-1024 107.31 ( 0.00%) 72.54 ( 32.40%)
Amean free-odr0-2048 108.92 ( 0.00%) 78.08 ( 28.32%)
Amean free-odr0-4096 113.38 ( 0.00%) 82.23 ( 27.48%)
Amean free-odr0-8192 112.08 ( 0.00%) 82.85 ( 26.08%)
Amean free-odr0-16384 110.38 ( 0.00%) 81.92 ( 25.78%)
Amean total-odr0-1 452.15 ( 0.00%) 308.00 ( 31.88%)
Amean total-odr0-2 334.23 ( 0.00%) 246.23 ( 26.33%)
Amean total-odr0-4 286.00 ( 0.00%) 205.38 ( 28.19%)
Amean total-odr0-8 255.54 ( 0.00%) 180.15 ( 29.50%)
Amean total-odr0-16 239.00 ( 0.00%) 169.00 ( 29.29%)
Amean total-odr0-32 229.00 ( 0.00%) 162.69 ( 28.96%)
Amean total-odr0-64 211.38 ( 0.00%) 159.00 ( 24.78%)
Amean total-odr0-128 223.00 ( 0.00%) 160.00 ( 28.25%)
Amean total-odr0-256 216.62 ( 0.00%) 182.00 ( 15.98%)
Amean total-odr0-512 244.31 ( 0.00%) 186.46 ( 23.68%)
Amean total-odr0-1024 254.54 ( 0.00%) 198.69 ( 21.94%)
Amean total-odr0-2048 264.08 ( 0.00%) 208.00 ( 21.24%)
Amean total-odr0-4096 277.38 ( 0.00%) 219.00 ( 21.05%)
Amean total-odr0-8192 279.00 ( 0.00%) 220.92 ( 20.82%)
Amean total-odr0-16384 269.38 ( 0.00%) 219.92 ( 18.36%)
This is the alloc, free and total overhead of allocating order-0 pages
in batches of 1 page up to 16384 pages. Avoiding disabling/enabling
overhead massively reduces overhead. Alloc overhead is roughly reduced
by 14-20% in most cases. The free path is reduced by 26-46% and the
total reduction is significant.
Many users require zeroing of pages from the page allocator which is the
vast cost of allocation. Hence, the impact on a basic page faulting
benchmark is not that significant
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Hmean page_test 656632.98 ( 0.00%) 675536.13 ( 2.88%)
Hmean brk_test 3845502.67 ( 0.00%) 3867186.94 ( 0.56%)
Stddev page_test 10543.29 ( 0.00%) 4104.07 ( 61.07%)
Stddev brk_test 33472.36 ( 0.00%) 15538.39 ( 53.58%)
CoeffVar page_test 1.61 ( 0.00%) 0.61 ( 62.15%)
CoeffVar brk_test 0.87 ( 0.00%) 0.40 ( 53.84%)
Max page_test 666513.33 ( 0.00%) 678640.00 ( 1.82%)
Max brk_test 3882800.00 ( 0.00%) 3887008.66 ( 0.11%)
This is from aim9 and the most notable outcome is that fault variability
is reduced by the patch. The headline improvement is small as the
overall fault cost, zeroing, page table insertion etc dominate relative
to disabling/enabling IRQs in the per-cpu allocator.
Similarly, little benefit was seen on networking benchmarks both
localhost and between physical server/clients where other costs
dominate. It's possible that this will only be noticable on very high
speed networks.
Jesper Dangaard Brouer independently tested this with a separate
microbenchmark from
https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/bench
Micro-benchmarked with [1] page_bench02:
modprobe page_bench02 page_order=0 run_flags=$((2#010)) loops=$((10**8)); \
rmmod page_bench02 ; dmesg --notime | tail -n 4
Compared to baseline: 213 cycles(tsc) 53.417 ns
- against this : 184 cycles(tsc) 46.056 ns
- Saving : -29 cycles
- Very close to expected 27 cycles saving [see below [2]]
Micro benchmarking via time_bench_sample[3], we get the cost of these
operations:
time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.232 ns (step:0)
time_bench: Type:spin_lock_unlock Per elem: 33 cycles(tsc) 8.334 ns (step:0)
time_bench: Type:spin_lock_unlock_irqsave Per elem: 62 cycles(tsc) 15.607 ns (step:0)
time_bench: Type:irqsave_before_lock Per elem: 57 cycles(tsc) 14.344 ns (step:0)
time_bench: Type:spin_lock_unlock_irq Per elem: 34 cycles(tsc) 8.560 ns (step:0)
time_bench: Type:simple_irq_disable_before_lock Per elem: 37 cycles(tsc) 9.289 ns (step:0)
time_bench: Type:local_BH_disable_enable Per elem: 19 cycles(tsc) 4.920 ns (step:0)
time_bench: Type:local_IRQ_disable_enable Per elem: 7 cycles(tsc) 1.864 ns (step:0)
time_bench: Type:local_irq_save_restore Per elem: 38 cycles(tsc) 9.665 ns (step:0)
[Mel's patch removes a ^^^^^^^^^^^^^^^^] ^^^^^^^^^ expected saving - preempt cost
time_bench: Type:preempt_disable_enable Per elem: 11 cycles(tsc) 2.794 ns (step:0)
[adds a preempt ^^^^^^^^^^^^^^^^^^^^^^] ^^^^^^^^^ adds this cost
time_bench: Type:funcion_call_cost Per elem: 6 cycles(tsc) 1.689 ns (step:0)
time_bench: Type:func_ptr_call_cost Per elem: 11 cycles(tsc) 2.767 ns (step:0)
time_bench: Type:page_alloc_put Per elem: 211 cycles(tsc) 52.803 ns (step:0)
Thus, expected improvement is: 38-11 = 27 cycles.
[mgorman@techsingularity.net: s/preempt_enable_no_resched/preempt_enable/]
Link: http://lkml.kernel.org/r/20170208143128.25ahymqlyspjcixu@techsingularity.net
Link: http://lkml.kernel.org/r/20170123153906.3122-5-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Dmitry has reported the following lockdep splat
lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3753
__mutex_lock_common kernel/locking/mutex.c:521 [inline]
mutex_lock_nested+0x24e/0xff0 kernel/locking/mutex.c:621
pcpu_alloc+0xbda/0x1280 mm/percpu.c:896
__alloc_percpu+0x24/0x30 mm/percpu.c:1075
smpcfd_prepare_cpu+0x73/0xd0 kernel/smp.c:44
cpuhp_invoke_callback+0x254/0x1480 kernel/cpu.c:136
cpuhp_up_callbacks+0x81/0x2a0 kernel/cpu.c:493
_cpu_up+0x1e3/0x2a0 kernel/cpu.c:1057
do_cpu_up+0x73/0xa0 kernel/cpu.c:1087
cpu_up+0x18/0x20 kernel/cpu.c:1095
smp_init+0xe9/0xee kernel/smp.c:564
kernel_init_freeable+0x439/0x690 init/main.c:1010
kernel_init+0x13/0x180 init/main.c:941
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
cpu_hotplug_begin
cpu_hotplug.lock
pcpu_alloc
pcpu_alloc_mutex
get_online_cpus+0x62/0x90 kernel/cpu.c:248
drain_all_pages+0xf8/0x710 mm/page_alloc.c:2385
__alloc_pages_direct_reclaim mm/page_alloc.c:3440 [inline]
__alloc_pages_slowpath+0x8fd/0x2370 mm/page_alloc.c:3778
__alloc_pages_nodemask+0x8f5/0xc60 mm/page_alloc.c:3980
__alloc_pages include/linux/gfp.h:426 [inline]
__alloc_pages_node include/linux/gfp.h:439 [inline]
alloc_pages_node include/linux/gfp.h:453 [inline]
pcpu_alloc_pages mm/percpu-vm.c:93 [inline]
pcpu_populate_chunk+0x1e1/0x900 mm/percpu-vm.c:282
pcpu_alloc+0xe01/0x1280 mm/percpu.c:998
__alloc_percpu_gfp+0x27/0x30 mm/percpu.c:1062
bpf_array_alloc_percpu kernel/bpf/arraymap.c:34 [inline]
array_map_alloc+0x532/0x710 kernel/bpf/arraymap.c:99
find_and_alloc_map kernel/bpf/syscall.c:34 [inline]
map_create kernel/bpf/syscall.c:188 [inline]
SYSC_bpf kernel/bpf/syscall.c:870 [inline]
SyS_bpf+0xd64/0x2500 kernel/bpf/syscall.c:827
entry_SYSCALL_64_fastpath+0x1f/0xc2
pcpu_alloc
pcpu_alloc_mutex
drain_all_pages
get_online_cpus
cpu_hotplug.lock
cpu_hotplug_begin+0x206/0x2e0 kernel/cpu.c:304
_cpu_up+0xca/0x2a0 kernel/cpu.c:1011
do_cpu_up+0x73/0xa0 kernel/cpu.c:1087
cpu_up+0x18/0x20 kernel/cpu.c:1095
smp_init+0xe9/0xee kernel/smp.c:564
kernel_init_freeable+0x439/0x690 init/main.c:1010
kernel_init+0x13/0x180 init/main.c:941
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
cpu_hotplug_begin
cpu_hotplug.lock
Pulling cpu hotplug locks inside the page allocator is just too
dangerous. Let's remove the dependency by dropping get_online_cpus()
from drain_all_pages. This is not so simple though because now we do
not have a protection against cpu hotplug which means 2 things:
- the work item might be executed on a different cpu in worker from
unbound pool so it doesn't run on pinned on the cpu
- we have to make sure that we do not race with page_alloc_cpu_dead
calling drain_pages_zone
Disabling preemption in drain_local_pages_wq will solve the first
problem drain_local_pages will determine its local CPU from the WQ
context which will be stable after that point, page_alloc_cpu_dead is
pinned to the CPU already. The later condition is achieved by disabling
IRQs in drain_pages_zone.
Fixes: mm, page_alloc: drain per-cpu pages from workqueue context
Link: http://lkml.kernel.org/r/20170207201950.20482-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The per-cpu page allocator can be drained immediately via
drain_all_pages() which sends IPIs to every CPU. In the next patch, the
per-cpu allocator will only be used for interrupt-safe allocations which
prevents draining it from IPI context. This patch uses workqueues to
drain the per-cpu lists instead.
This is slower but no slowdown during intensive reclaim was measured and
the paths that use drain_all_pages() are not that sensitive to
performance. This is particularly true as the path would only be
triggered when reclaim is failing. It also makes a some sense to avoid
storming a machine with IPIs when it's under memory pressure. Arguably,
it should be further adjusted so that only one caller at a time is
draining pages but it's beyond the scope of the current patch.
Link: http://lkml.kernel.org/r/20170123153906.3122-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Michal Hocko