__GFP_WAIT has been used to identify atomic context in callers that hold
spinlocks or are in interrupts. They are expected to be high priority and
have access one of two watermarks lower than "min" which can be referred
to as the "atomic reserve". __GFP_HIGH users get access to the first
lower watermark and can be called the "high priority reserve".
Over time, callers had a requirement to not block when fallback options
were available. Some have abused __GFP_WAIT leading to a situation where
an optimisitic allocation with a fallback option can access atomic
reserves.
This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
cannot sleep and have no alternative. High priority users continue to use
__GFP_HIGH. __GFP_DIRECT_RECLAIM identifies callers that can sleep and
are willing to enter direct reclaim. __GFP_KSWAPD_RECLAIM to identify
callers that want to wake kswapd for background reclaim. __GFP_WAIT is
redefined as a caller that is willing to enter direct reclaim and wake
kswapd for background reclaim.
This patch then converts a number of sites
o __GFP_ATOMIC is used by callers that are high priority and have memory
pools for those requests. GFP_ATOMIC uses this flag.
o Callers that have a limited mempool to guarantee forward progress clear
__GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
into this category where kswapd will still be woken but atomic reserves
are not used as there is a one-entry mempool to guarantee progress.
o Callers that are checking if they are non-blocking should use the
helper gfpflags_allow_blocking() where possible. This is because
checking for __GFP_WAIT as was done historically now can trigger false
positives. Some exceptions like dm-crypt.c exist where the code intent
is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
flag manipulations.
o Callers that built their own GFP flags instead of starting with GFP_KERNEL
and friends now also need to specify __GFP_KSWAPD_RECLAIM.
The first key hazard to watch out for is callers that removed __GFP_WAIT
and was depending on access to atomic reserves for inconspicuous reasons.
In some cases it may be appropriate for them to use __GFP_HIGH.
The second key hazard is callers that assembled their own combination of
GFP flags instead of starting with something like GFP_KERNEL. They may
now wish to specify __GFP_KSWAPD_RECLAIM. It's almost certainly harmless
if it's missed in most cases as other activity will wake kswapd.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@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>
We have memcg_kmem_charge and memcg_kmem_uncharge methods for charging and
uncharging kmem pages to memcg, but currently they are not used for
charging slab pages (i.e. they are only used for charging pages allocated
with alloc_kmem_pages). The only reason why the slab subsystem uses
special helpers, memcg_charge_slab and memcg_uncharge_slab, is that it
needs to charge to the memcg of kmem cache while memcg_charge_kmem charges
to the memcg that the current task belongs to.
To remove this diversity, this patch adds an extra argument to
__memcg_kmem_charge that can be a pointer to a memcg or NULL. If it is
not NULL, the function tries to charge to the memcg it points to,
otherwise it charge to the current context. Next, it makes the slab
subsystem use this function to charge slab pages.
Since memcg_charge_kmem and memcg_uncharge_kmem helpers are now used only
in __memcg_kmem_charge and __memcg_kmem_uncharge, they are inlined. Since
__memcg_kmem_charge stores a pointer to the memcg in the page struct, we
don't need memcg_uncharge_slab anymore and can use free_kmem_pages.
Besides, one can now detect which memcg a slab page belongs to by reading
/proc/kpagecgroup.
Note, this patch switches slab to charge-after-alloc design. Since this
design is already used for all other memcg charges, it should not make any
difference.
[hannes@cmpxchg.org: better to have an outer function than a magic parameter for the memcg lookup]
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
On systems with a KMALLOC_MIN_SIZE of 128 (arm64, some mips and powerpc
configurations defining ARCH_DMA_MINALIGN to 128), the first
kmalloc_caches[] entry to be initialised after slab_early_init = 0 is
"kmalloc-128" with index 7. Depending on the debug kernel configuration,
sizeof(struct kmem_cache) can be larger than 128 resulting in an
INDEX_NODE of 8.
Commit 8fc9cf420b ("slab: make more slab management structure off the
slab") enables off-slab management objects for sizes starting with
PAGE_SIZE >> 5 (128 bytes for a 4KB page configuration) and the creation
of the "kmalloc-128" cache would try to place the management objects
off-slab. However, since KMALLOC_MIN_SIZE is already 128 and
freelist_size == 32 in __kmem_cache_create(), kmalloc_slab(freelist_size)
returns NULL (kmalloc_caches[7] not populated yet). This triggers the
following bug on arm64:
kernel BUG at /work/Linux/linux-2.6-aarch64/mm/slab.c:2283!
Internal error: Oops - BUG: 0 [#1] SMP
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 4.3.0-rc4+ #540
Hardware name: Juno (DT)
PC is at __kmem_cache_create+0x21c/0x280
LR is at __kmem_cache_create+0x210/0x280
[...]
Call trace:
__kmem_cache_create+0x21c/0x280
create_boot_cache+0x48/0x80
create_kmalloc_cache+0x50/0x88
create_kmalloc_caches+0x4c/0xf4
kmem_cache_init+0x100/0x118
start_kernel+0x214/0x33c
This patch introduces an OFF_SLAB_MIN_SIZE definition to avoid off-slab
management objects for sizes equal to or smaller than KMALLOC_MIN_SIZE.
Fixes: 8fc9cf420b ("slab: make more slab management structure off the slab")
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org> [3.15+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit description is copied from the original post of this bug:
http://comments.gmane.org/gmane.linux.kernel.mm/135349
Kernels after v3.9 use kmalloc_size(INDEX_NODE + 1) to get the next
larger cache size than the size index INDEX_NODE mapping. In kernels
3.9 and earlier we used malloc_sizes[INDEX_L3 + 1].cs_size.
However, sometimes we can't get the right output we expected via
kmalloc_size(INDEX_NODE + 1), causing a BUG().
The mapping table in the latest kernel is like:
index = {0, 1, 2 , 3, 4, 5, 6, n}
size = {0, 96, 192, 8, 16, 32, 64, 2^n}
The mapping table before 3.10 is like this:
index = {0 , 1 , 2, 3, 4 , 5 , 6, n}
size = {32, 64, 96, 128, 192, 256, 512, 2^(n+3)}
The problem on my mips64 machine is as follows:
(1) When configured DEBUG_SLAB && DEBUG_PAGEALLOC && DEBUG_LOCK_ALLOC
&& DEBUG_SPINLOCK, the sizeof(struct kmem_cache_node) will be "150",
and the macro INDEX_NODE turns out to be "2": #define INDEX_NODE
kmalloc_index(sizeof(struct kmem_cache_node))
(2) Then the result of kmalloc_size(INDEX_NODE + 1) is 8.
(3) Then "if(size >= kmalloc_size(INDEX_NODE + 1)" will lead to "size
= PAGE_SIZE".
(4) Then "if ((size >= (PAGE_SIZE >> 3))" test will be satisfied and
"flags |= CFLGS_OFF_SLAB" will be covered.
(5) if (flags & CFLGS_OFF_SLAB)" test will be satisfied and will go to
"cachep->slabp_cache = kmalloc_slab(slab_size, 0u)", and the result
here may be NULL while kernel bootup.
(6) Finally,"BUG_ON(ZERO_OR_NULL_PTR(cachep->slabp_cache));" causes the
BUG info as the following shows (may be only mips64 has this problem):
This patch fixes the problem of kmalloc_size(INDEX_NODE + 1) and removes
the BUG by adding 'size >= 256' check to guarantee that all necessary
small sized slabs are initialized regardless sequence of slab size in
mapping table.
Fixes: e33660165c ("slab: Use common kmalloc_index/kmalloc_size...")
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reported-by: Liuhailong <liu.hailong6@zte.com.cn>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
alloc_pages_exact_node() was introduced in commit 6484eb3e2a ("page
allocator: do not check NUMA node ID when the caller knows the node is
valid") as an optimized variant of alloc_pages_node(), that doesn't
fallback to current node for nid == NUMA_NO_NODE. Unfortunately the
name of the function can easily suggest that the allocation is
restricted to the given node and fails otherwise. In truth, the node is
only preferred, unless __GFP_THISNODE is passed among the gfp flags.
The misleading name has lead to mistakes in the past, see for example
commits 5265047ac3 ("mm, thp: really limit transparent hugepage
allocation to local node") and b360edb43f ("mm, mempolicy:
migrate_to_node should only migrate to node").
Another issue with the name is that there's a family of
alloc_pages_exact*() functions where 'exact' means exact size (instead
of page order), which leads to more confusion.
To prevent further mistakes, this patch effectively renames
alloc_pages_exact_node() to __alloc_pages_node() to better convey that
it's an optimized variant of alloc_pages_node() not intended for general
usage. Both functions get described in comments.
It has been also considered to really provide a convenience function for
allocations restricted to a node, but the major opinion seems to be that
__GFP_THISNODE already provides that functionality and we shouldn't
duplicate the API needlessly. The number of users would be small
anyway.
Existing callers of alloc_pages_exact_node() are simply converted to
call __alloc_pages_node(), with the exception of sba_alloc_coherent()
which open-codes the check for NUMA_NO_NODE, so it is converted to use
alloc_pages_node() instead. This means it no longer performs some
VM_BUG_ON checks, and since the current check for nid in
alloc_pages_node() uses a 'nid < 0' comparison (which includes
NUMA_NO_NODE), it may hide wrong values which would be previously
exposed.
Both differences will be rectified by the next patch.
To sum up, this patch makes no functional changes, except temporarily
hiding potentially buggy callers. Restricting the checks in
alloc_pages_node() is left for the next patch which can in turn expose
more existing buggy callers.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Robin Holt <robinmholt@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mel Gorman <mgorman@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Cliff Whickman <cpw@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add the basic infrastructure for alloc/free operations on pointer arrays.
It includes a generic function in the common slab code that is used in
this infrastructure patch to create the unoptimized functionality for slab
bulk operations.
Allocators can then provide optimized allocation functions for situations
in which large numbers of objects are needed. These optimization may
avoid taking locks repeatedly and bypass metadata creation if all objects
in slab pages can be used to provide the objects required.
Allocators can extend the skeletons provided and add their own code to the
bulk alloc and free functions. They can keep the generic allocation and
freeing and just fall back to those if optimizations would not work (like
for example when debugging is on).
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
Commit c48a11c7ad ("netvm: propagate page->pfmemalloc to skb") added
checks for page->pfmemalloc to __skb_fill_page_desc():
if (page->pfmemalloc && !page->mapping)
skb->pfmemalloc = true;
It assumes page->mapping == NULL implies that page->pfmemalloc can be
trusted. However, __delete_from_page_cache() can set set page->mapping
to NULL and leave page->index value alone. Due to being in union, a
non-zero page->index will be interpreted as true page->pfmemalloc.
So the assumption is invalid if the networking code can see such a page.
And it seems it can. We have encountered this with a NFS over loopback
setup when such a page is attached to a new skbuf. There is no copying
going on in this case so the page confuses __skb_fill_page_desc which
interprets the index as pfmemalloc flag and the network stack drops
packets that have been allocated using the reserves unless they are to
be queued on sockets handling the swapping which is the case here and
that leads to hangs when the nfs client waits for a response from the
server which has been dropped and thus never arrive.
The struct page is already heavily packed so rather than finding another
hole to put it in, let's do a trick instead. We can reuse the index
again but define it to an impossible value (-1UL). This is the page
index so it should never see the value that large. Replace all direct
users of page->pfmemalloc by page_is_pfmemalloc which will hide this
nastiness from unspoiled eyes.
The information will get lost if somebody wants to use page->index
obviously but that was the case before and the original code expected
that the information should be persisted somewhere else if that is
really needed (e.g. what SLAB and SLUB do).
[akpm@linux-foundation.org: fix blooper in slub]
Fixes: c48a11c7ad ("netvm: propagate page->pfmemalloc to skb")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Debugged-by: Vlastimil Babka <vbabka@suse.com>
Debugged-by: Jiri Bohac <jbohac@suse.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org> [3.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch moves the initialization of the size_index table slightly
earlier so that the first few kmem_cache_node's can be safely allocated
when KMALLOC_MIN_SIZE is large.
There are currently two ways to generate indices into kmalloc_caches (via
kmalloc_index() and via the size_index table in slab_common.c) and on some
arches (possibly only MIPS) they potentially disagree with each other
until create_kmalloc_caches() has been called. It seems that the
intention is that the size_index table is a fast equivalent to
kmalloc_index() and that create_kmalloc_caches() patches the table to
return the correct value for the cases where kmalloc_index()'s
if-statements apply.
The failing sequence was:
* kmalloc_caches contains NULL elements
* kmem_cache_init initialises the element that 'struct
kmem_cache_node' will be allocated to. For 32-bit Mips, this is a
56-byte struct and kmalloc_index returns KMALLOC_SHIFT_LOW (7).
* init_list is called which calls kmalloc_node to allocate a 'struct
kmem_cache_node'.
* kmalloc_slab selects the kmem_caches element using
size_index[size_index_elem(size)]. For MIPS, size is 56, and the
expression returns 6.
* This element of kmalloc_caches is NULL and allocation fails.
* If it had not already failed, it would have called
create_kmalloc_caches() at this point which would have changed
size_index[size_index_elem(size)] to 7.
I don't believe the bug to be LLVM specific but GCC doesn't normally
encounter the problem. I haven't been able to identify exactly what GCC
is doing better (probably inlining) but it seems that GCC is managing to
optimize to the point that it eliminates the problematic allocations.
This theory is supported by the fact that GCC can be made to fail in the
same way by changing inline, __inline, __inline__, and __always_inline in
include/linux/compiler-gcc.h such that they don't actually inline things.
Signed-off-by: Daniel Sanders <daniel.sanders@imgtec.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
NOTE: this is not about __GFP_THISNODE, this is only about GFP_THISNODE.
GFP_THISNODE is a secret combination of gfp bits that have different
behavior than expected. It is a combination of __GFP_THISNODE,
__GFP_NORETRY, and __GFP_NOWARN and is special-cased in the page
allocator slowpath to fail without trying reclaim even though it may be
used in combination with __GFP_WAIT.
An example of the problem this creates: commit e97ca8e5b8 ("mm: fix
GFP_THISNODE callers and clarify") fixed up many users of GFP_THISNODE
that really just wanted __GFP_THISNODE. The problem doesn't end there,
however, because even it was a no-op for alloc_misplaced_dst_page(),
which also sets __GFP_NORETRY and __GFP_NOWARN, and
migrate_misplaced_transhuge_page(), where __GFP_NORETRY and __GFP_NOWAIT
is set in GFP_TRANSHUGE. Converting GFP_THISNODE to __GFP_THISNODE is a
no-op in these cases since the page allocator special-cases
__GFP_THISNODE && __GFP_NORETRY && __GFP_NOWARN.
It's time to just remove GFP_THISNODE entirely. We leave __GFP_THISNODE
to restrict an allocation to a local node, but remove GFP_THISNODE and
its obscurity. Instead, we require that a caller clear __GFP_WAIT if it
wants to avoid reclaim.
This allows the aforementioned functions to actually reclaim as they
should. It also enables any future callers that want to do
__GFP_THISNODE but also __GFP_NORETRY && __GFP_NOWARN to reclaim. The
rule is simple: if you don't want to reclaim, then don't set __GFP_WAIT.
Aside: ovs_flow_stats_update() really wants to avoid reclaim as well, so
it is unchanged.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Pravin Shelar <pshelar@nicira.com>
Cc: Jarno Rajahalme <jrajahalme@nicira.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Greg Thelen <gthelen@google.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>
To speed up further allocations SLUB may store empty slabs in per cpu/node
partial lists instead of freeing them immediately. This prevents per
memcg caches destruction, because kmem caches created for a memory cgroup
are only destroyed after the last page charged to the cgroup is freed.
To fix this issue, this patch resurrects approach first proposed in [1].
It forbids SLUB to cache empty slabs after the memory cgroup that the
cache belongs to was destroyed. It is achieved by setting kmem_cache's
cpu_partial and min_partial constants to 0 and tuning put_cpu_partial() so
that it would drop frozen empty slabs immediately if cpu_partial = 0.
The runtime overhead is minimal. From all the hot functions, we only
touch relatively cold put_cpu_partial(): we make it call
unfreeze_partials() after freezing a slab that belongs to an offline
memory cgroup. Since slab freezing exists to avoid moving slabs from/to a
partial list on free/alloc, and there can't be allocations from dead
caches, it shouldn't cause any overhead. We do have to disable preemption
for put_cpu_partial() to achieve that though.
The original patch was accepted well and even merged to the mm tree.
However, I decided to withdraw it due to changes happening to the memcg
core at that time. I had an idea of introducing per-memcg shrinkers for
kmem caches, but now, as memcg has finally settled down, I do not see it
as an option, because SLUB shrinker would be too costly to call since SLUB
does not keep free slabs on a separate list. Besides, we currently do not
even call per-memcg shrinkers for offline memcgs. Overall, it would
introduce much more complexity to both SLUB and memcg than this small
patch.
Regarding to SLAB, there's no problem with it, because it shrinks
per-cpu/node caches periodically. Thanks to list_lru reparenting, we no
longer keep entries for offline cgroups in per-memcg arrays (such as
memcg_cache_params->memcg_caches), so we do not have to bother if a
per-memcg cache will be shrunk a bit later than it could be.
[1] http://thread.gmane.org/gmane.linux.kernel.mm/118649/focus=118650
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
Sometimes, we need to iterate over all memcg copies of a particular root
kmem cache. Currently, we use memcg_cache_params->memcg_caches array for
that, because it contains all existing memcg caches.
However, it's a bad practice to keep all caches, including those that
belong to offline cgroups, in this array, because it will be growing
beyond any bounds then. I'm going to wipe away dead caches from it to
save space. To still be able to perform iterations over all memcg caches
of the same kind, let us link them into a list.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fallback_alloc is called on kmalloc if the preferred node doesn't have
free or partial slabs and there's no pages on the node's free list
(GFP_THISNODE allocations fail). Before invoking the reclaimer it tries
to locate a free or partial slab on other allowed nodes' lists. While
iterating over the preferred node's zonelist it skips those zones which
hardwall cpuset check returns false for. That means that for a task bound
to a specific node using cpusets fallback_alloc will always ignore free
slabs on other nodes and go directly to the reclaimer, which, however, may
allocate from other nodes if cpuset.mem_hardwall is unset (default). As a
result, we may get lists of free slabs grow without bounds on other nodes,
which is bad, because inactive slabs are only evicted by cache_reap at a
very slow rate and cannot be dropped forcefully.
To reproduce the issue, run a process that will walk over a directory tree
with lots of files inside a cpuset bound to a node that constantly
experiences memory pressure. Look at num_slabs vs active_slabs growth as
reported by /proc/slabinfo.
To avoid this we should use softwall cpuset check in fallback_alloc.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Zefan Li <lizefan@huawei.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.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>
Suppose task @t that belongs to a memory cgroup @memcg is going to
allocate an object from a kmem cache @c. The copy of @c corresponding to
@memcg, @mc, is empty. Then if kmem_cache_alloc races with the memory
cgroup destruction we can access the memory cgroup's copy of the cache
after it was destroyed:
CPU0 CPU1
---- ----
[ current=@t
@mc->memcg_params->nr_pages=0 ]
kmem_cache_alloc(@c):
call memcg_kmem_get_cache(@c);
proceed to allocation from @mc:
alloc a page for @mc:
...
move @t from @memcg
destroy @memcg:
mem_cgroup_css_offline(@memcg):
memcg_unregister_all_caches(@memcg):
kmem_cache_destroy(@mc)
add page to @mc
We could fix this issue by taking a reference to a per-memcg cache, but
that would require adding a per-cpu reference counter to per-memcg caches,
which would look cumbersome.
Instead, let's take a reference to a memory cgroup, which already has a
per-cpu reference counter, in the beginning of kmem_cache_alloc to be
dropped in the end, and move per memcg caches destruction from css offline
to css free. As a side effect, per-memcg caches will be destroyed not one
by one, but all at once when the last page accounted to the memory cgroup
is freed. This doesn't sound as a high price for code readability though.
Note, this patch does add some overhead to the kmem_cache_alloc hot path,
but it is pretty negligible - it's just a function call plus a per cpu
counter decrement, which is comparable to what we already have in
memcg_kmem_get_cache. Besides, it's only relevant if there are memory
cgroups with kmem accounting enabled. I don't think we can find a way to
handle this race w/o it, because alloc_page called from kmem_cache_alloc
may sleep so we can't flush all pending kmallocs w/o reference counting.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
Pull cgroup update from Tejun Heo:
"cpuset got simplified a bit. cgroup core got a fix on unified
hierarchy and grew some effective css related interfaces which will be
used for blkio support for writeback IO traffic which is currently
being worked on"
* 'for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: implement cgroup_get_e_css()
cgroup: add cgroup_subsys->css_e_css_changed()
cgroup: add cgroup_subsys->css_released()
cgroup: fix the async css offline wait logic in cgroup_subtree_control_write()
cgroup: restructure child_subsys_mask handling in cgroup_subtree_control_write()
cgroup: separate out cgroup_calc_child_subsys_mask() from cgroup_refresh_child_subsys_mask()
cpuset: lock vs unlock typo
cpuset: simplify cpuset_node_allowed API
cpuset: convert callback_mutex to a spinlock
The code goes BUG, but doesn't tell us which bits were unexpectedly set.
Print that out.
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
Currently we print the slabinfo header in the seq start method, which
makes it unusable for showing leaks, so we have leaks_show, which does
practically the same as s_show except it doesn't show the header.
However, we can print the header in the seq show method - we only need
to check if the current element is the first on the list. This will
allow us to use the same set of seq iterators for both leaks and
slabinfo reporting, which is nice.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some code in mm/slab.c and mm/slub.c use whitespaces in indent.
Clean them up.
Signed-off-by: LQYMGT <lqymgt@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
The bounds check for nodeid in ____cache_alloc_node gives false
positives on machines where the node IDs are not contiguous, leading to
a panic at boot time. For example, on a POWER8 machine the node IDs are
typically 0, 1, 16 and 17. This means that num_online_nodes() returns
4, so when ____cache_alloc_node is called with nodeid = 16 the VM_BUG_ON
triggers, like this:
kernel BUG at /home/paulus/kernel/kvm/mm/slab.c:3079!
Call Trace:
.____cache_alloc_node+0x5c/0x270 (unreliable)
.kmem_cache_alloc_node_trace+0xdc/0x360
.init_list+0x3c/0x128
.kmem_cache_init+0x1dc/0x258
.start_kernel+0x2a0/0x568
start_here_common+0x20/0xa8
To fix this, we instead compare the nodeid with MAX_NUMNODES, and
additionally make sure it isn't negative (since nodeid is an int). The
check is there mainly to protect the array dereference in the get_node()
call in the next line, and the array being dereferenced is of size
MAX_NUMNODES. If the nodeid is in range but invalid (for example if the
node is off-line), the BUG_ON in the next line will catch that.
Fixes: 14e50c6a9b ("mm: slab: Verify the nodeid passed to ____cache_alloc_node")
Signed-off-by: Paul Mackerras <paulus@samba.org>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Current cpuset API for checking if a zone/node is allowed to allocate
from looks rather awkward. We have hardwall and softwall versions of
cpuset_node_allowed with the softwall version doing literally the same
as the hardwall version if __GFP_HARDWALL is passed to it in gfp flags.
If it isn't, the softwall version may check the given node against the
enclosing hardwall cpuset, which it needs to take the callback lock to
do.
Such a distinction was introduced by commit 02a0e53d82 ("cpuset:
rework cpuset_zone_allowed api"). Before, we had the only version with
the __GFP_HARDWALL flag determining its behavior. The purpose of the
commit was to avoid sleep-in-atomic bugs when someone would mistakenly
call the function without the __GFP_HARDWALL flag for an atomic
allocation. The suffixes introduced were intended to make the callers
think before using the function.
However, since the callback lock was converted from mutex to spinlock by
the previous patch, the softwall check function cannot sleep, and these
precautions are no longer necessary.
So let's simplify the API back to the single check.
Suggested-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Commit bf0dea23a9 ("mm/slab: use percpu allocator for cpu cache")
changed the allocation method for cpu cache array from slab allocator to
percpu allocator. Alignment should be provided for aligned memory in
percpu allocator case, but, that commit mistakenly set this alignment to
0. So, percpu allocator returns unaligned memory address. It doesn't
cause any problem on x86 which permits unaligned access, but, it causes
the problem on sparc64 which needs strong guarantee of alignment.
Following bug report is reported from David Miller.
I'm getting tons of the following on sparc64:
[603965.383447] Kernel unaligned access at TPC[546b58] free_block+0x98/0x1a0
[603965.396987] Kernel unaligned access at TPC[546b60] free_block+0xa0/0x1a0
...
[603970.554394] log_unaligned: 333 callbacks suppressed
...
This patch provides a proper alignment parameter when allocating cpu
cache to fix this unaligned memory access problem on sparc64.
Reported-by: David Miller <davem@davemloft.net>
Tested-by: David Miller <davem@davemloft.net>
Tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Using __seq_open_private() removes boilerplate code from slabstats_open()
The resultant code is shorter and easier to follow.
This patch does not change any functionality.
Signed-off-by: Rob Jones <rob.jones@codethink.co.uk>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
Because of chicken and egg problem, initialization of SLAB is really
complicated. We need to allocate cpu cache through SLAB to make the
kmem_cache work, but before initialization of kmem_cache, allocation
through SLAB is impossible.
On the other hand, SLUB does initialization in a more simple way. It uses
percpu allocator to allocate cpu cache so there is no chicken and egg
problem.
So, this patch try to use percpu allocator in SLAB. This simplifies the
initialization step in SLAB so that we could maintain SLAB code more
easily.
In my testing there is no performance difference.
This implementation relies on percpu allocator. Because percpu allocator
uses vmalloc address space, vmalloc address space could be exhausted by
this change on many cpu system with *32 bit* kernel. This implementation
can cover 1024 cpus in worst case by following calculation.
Worst: 1024 cpus * 4 bytes for pointer * 300 kmem_caches *
120 objects per cpu_cache = 140 MB
Normal: 1024 cpus * 4 bytes for pointer * 150 kmem_caches(slab merge) *
80 objects per cpu_cache = 46 MB
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Slab merge is good feature to reduce fragmentation. If new creating slab
have similar size and property with exsitent slab, this feature reuse it
rather than creating new one. As a result, objects are packed into fewer
slabs so that fragmentation is reduced.
Below is result of my testing.
* After boot, sleep 20; cat /proc/meminfo | grep Slab
<Before>
Slab: 25136 kB
<After>
Slab: 24364 kB
We can save 3% memory used by slab.
For supporting this feature in SLAB, we need to implement SLAB specific
kmem_cache_flag() and __kmem_cache_alias(), because SLUB implements some
SLUB specific processing related to debug flag and object size change on
these functions.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
cache_free_alien() is rarely used function when node mismatch. But, it is
defined with inline attribute so it is inlined to __cache_free() which is
core free function of slab allocator. It uselessly makes
kmem_cache_free()/kfree() functions large. What we really need to inline
is just checking node match so this patch factor out other parts of
cache_free_alien() to reduce code size of kmem_cache_free()/ kfree().
<Before>
nm -S mm/slab.o | grep -e "T kfree" -e "T kmem_cache_free"
00000000000011e0 0000000000000228 T kfree
0000000000000670 0000000000000216 T kmem_cache_free
<After>
nm -S mm/slab.o | grep -e "T kfree" -e "T kmem_cache_free"
0000000000001110 00000000000001b5 T kfree
0000000000000750 0000000000000181 T kmem_cache_free
You can see slightly reduced size of text: 0x228->0x1b5, 0x216->0x181.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Our intention of __ac_put_obj() is that it doesn't affect anything if
sk_memalloc_socks() is disabled. But, because __ac_put_obj() is too
small, compiler inline it to ac_put_obj() and affect code size of free
path. This patch add noinline keyword for __ac_put_obj() not to distrupt
normal free path at all.
<Before>
nm -S slab-orig.o |
grep -e "t cache_alloc_refill" -e "T kfree" -e "T kmem_cache_free"
0000000000001e80 00000000000002f5 t cache_alloc_refill
0000000000001230 0000000000000258 T kfree
0000000000000690 000000000000024c T kmem_cache_free
<After>
nm -S slab-patched.o |
grep -e "t cache_alloc_refill" -e "T kfree" -e "T kmem_cache_free"
0000000000001e00 00000000000002e5 t cache_alloc_refill
00000000000011e0 0000000000000228 T kfree
0000000000000670 0000000000000216 T kmem_cache_free
cache_alloc_refill: 0x2f5->0x2e5
kfree: 0x256->0x228
kmem_cache_free: 0x24c->0x216
code size of each function is reduced slightly.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now, due to likely keyword, compiled code of cache_flusharray() is on
unlikely.text section. Although it is uncommon case compared to free to
cpu cache case, it is common case than free_block(). But, free_block() is
on normal text section. This patch fix this odd situation to remove
likely keyword.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now, we track caller if tracing or slab debugging is enabled. If they are
disabled, we could save one argument passing overhead by calling
__kmalloc(_node)(). But, I think that it would be marginal. Furthermore,
default slab allocator, SLUB, doesn't use this technique so I think that
it's okay to change this situation.
After this change, we can turn on/off CONFIG_DEBUG_SLAB without full
kernel build and remove some complicated '#if' defintion. It looks more
benefitial to me.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull cgroup fixes from Tejun Heo:
"This is quite late but these need to be backported anyway.
This is the fix for a long-standing cpuset bug which existed from
2009. cpuset makes use of PF_SPREAD_{PAGE|SLAB} flags to modify the
task's memory allocation behavior according to the settings of the
cpuset it belongs to; unfortunately, when those flags have to be
changed, cpuset did so directly even whlie the target task is running,
which is obviously racy as task->flags may be modified by the task
itself at any time. This obscure bug manifested as corrupt
PF_USED_MATH flag leading to a weird crash.
The bug is fixed by moving the flag to task->atomic_flags. The first
two are prepatory ones to help defining atomic_flags accessors and the
third one is the actual fix"
* 'for-3.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cpuset: PF_SPREAD_PAGE and PF_SPREAD_SLAB should be atomic flags
sched: add macros to define bitops for task atomic flags
sched: fix confusing PFA_NO_NEW_PRIVS constant
Since commit 4590685546 ("mm/sl[aou]b: Common alignment code"), the
"ralign" automatic variable in __kmem_cache_create() may be used as
uninitialized.
The proper alignment defaults to BYTES_PER_WORD and can be overridden by
SLAB_RED_ZONE or the alignment specified by the caller.
This fixes https://bugzilla.kernel.org/show_bug.cgi?id=85031
Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Andrei Elovikov <a.elovikov@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When we change cpuset.memory_spread_{page,slab}, cpuset will flip
PF_SPREAD_{PAGE,SLAB} bit of tsk->flags for each task in that cpuset.
This should be done using atomic bitops, but currently we don't,
which is broken.
Tetsuo reported a hard-to-reproduce kernel crash on RHEL6, which happened
when one thread tried to clear PF_USED_MATH while at the same time another
thread tried to flip PF_SPREAD_PAGE/PF_SPREAD_SLAB. They both operate on
the same task.
Here's the full report:
https://lkml.org/lkml/2014/9/19/230
To fix this, we make PF_SPREAD_PAGE and PF_SPREAD_SLAB atomic flags.
v4:
- updated mm/slab.c. (Fengguang Wu)
- updated Documentation.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Cc: Kees Cook <keescook@chromium.org>
Fixes: 950592f7b9 ("cpusets: update tasks' page/slab spread flags in time")
Cc: <stable@vger.kernel.org> # 2.6.31+
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This reverts commit a640616822 ("slab: remove BAD_ALIEN_MAGIC").
commit a640616822 ("slab: remove BAD_ALIEN_MAGIC") assumes that the
system with !CONFIG_NUMA has only one memory node. But, it turns out to
be false by the report from Geert. His system, m68k, has many memory
nodes and is configured in !CONFIG_NUMA. So it couldn't boot with above
change.
Here goes his failure report.
With latest mainline, I'm getting a crash during bootup on m68k/ARAnyM:
enable_cpucache failed for radix_tree_node, error 12.
kernel BUG at /scratch/geert/linux/linux-m68k/mm/slab.c:1522!
*** TRAP #7 *** FORMAT=0
Current process id is 0
BAD KERNEL TRAP: 00000000
Modules linked in:
PC: [<0039c92c>] kmem_cache_init_late+0x70/0x8c
SR: 2200 SP: 00345f90 a2: 0034c2e8
d0: 0000003d d1: 00000000 d2: 00000000 d3: 003ac942
d4: 00000000 d5: 00000000 a0: 0034f686 a1: 0034f682
Process swapper (pid: 0, task=0034c2e8)
Frame format=0
Stack from 00345fc4:
002f69ef 002ff7e5 000005f2 000360fa 0017d806 003921d4 00000000
00000000 00000000 00000000 00000000 00000000 003ac942 00000000
003912d6
Call Trace: [<000360fa>] parse_args+0x0/0x2ca
[<0017d806>] strlen+0x0/0x1a
[<003921d4>] start_kernel+0x23c/0x428
[<003912d6>] _sinittext+0x2d6/0x95e
Code: f7e5 4879 002f 69ef 61ff ffca 462a 4e47 <4879> 0035 4b1c 61ff
fff0 0cc4 7005 23c0 0037 fd20 588f 265f 285f 4e75 48e7 301c
Disabling lock debugging due to kernel taint
Kernel panic - not syncing: Attempted to kill the idle task!
Although there is a alternative way to fix this issue such as disabling
use of alien cache on !CONFIG_NUMA, but, reverting issued commit is better
to me in this time.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Current struct kmem_cache has no 'lock' field, and slab page is managed by
struct kmem_cache_node, which has 'list_lock' field.
Clean up the related comment.
Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>
It is better to represent allocation size in size_t rather than int. So
change it.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
BAD_ALIEN_MAGIC value isn't used anymore. So remove it.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now, there is no code to hold two lock simultaneously, since we don't
call slab_destroy() with holding any lock. So, lockdep annotation is
useless now. Remove it.
v2: don't remove BAD_ALIEN_MAGIC in this patch. It will be removed
in the following patch.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I haven't heard that this alien cache lock is contended, but to reduce
chance of contention would be better generally. And with this change,
we can simplify complex lockdep annotation in slab code. In the
following patch, it will be implemented.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now, we have separate alien_cache structure, so it'd be better to hold
the lock on alien_cache while manipulating alien_cache. After that, we
don't need the lock on array_cache, so remove it.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, we use array_cache for alien_cache. Although they are mostly
similar, there is one difference, that is, need for spinlock. We don't
need spinlock for array_cache itself, but to use array_cache for
alien_cache, array_cache structure should have spinlock. This is
needless overhead, so removing it would be better. This patch prepare
it by introducing alien_cache and using it. In the following patch, we
remove spinlock in array_cache.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Factor out initialization of array cache to use it in following patch.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In free_block(), if freeing object makes new free slab and number of
free_objects exceeds free_limit, we start to destroy this new free slab
with holding the kmem_cache node lock. Holding the lock is useless and,
generally, holding a lock as least as possible is good thing. I never
measure performance effect of this, but we'd be better not to hold the
lock as much as possible.
Commented by Christoph:
This is also good because kmem_cache_free is no longer called while
holding the node lock. So we avoid one case of recursion.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
node isn't changed, so we don't need to retreive this structure
everytime we move the object. Maybe compiler do this optimization, but
making it explicitly is better.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patchset does some cleanup and tries to remove lockdep annotation.
Patches 1~2 are just for really really minor improvement.
Patches 3~9 are for clean-up and removing lockdep annotation.
There are two cases that lockdep annotation is needed in SLAB.
1) holding two node locks
2) holding two array cache(alien cache) locks
I looked at the code and found that we can avoid these cases without any
negative effect.
1) occurs if freeing object makes new free slab and we decide to
destroy it. Although we don't need to hold the lock during destroying
a slab, current code do that. Destroying a slab without holding the
lock would help the reduction of the lock contention. To do it, I
change the implementation that new free slab is destroyed after
releasing the lock.
2) occurs on similar situation. When we free object from non-local
node, we put this object to alien cache with holding the alien cache
lock. If alien cache is full, we try to flush alien cache to proper
node cache, and, in this time, new free slab could be made. Destroying
it would be started and we will free metadata object which comes from
another node. In this case, we need another node's alien cache lock to
free object. This forces us to hold two array cache locks and then we
need lockdep annotation although they are always different locks and
deadlock cannot be possible. To prevent this situation, I use same way
as 1).
In this way, we can avoid 1) and 2) cases, and then, can remove lockdep
annotation. As short stat noted, this makes SLAB code much simpler.
This patch (of 9):
slab_should_failslab() is called on every allocation, so to optimize it
is reasonable. We normally don't allocate from kmem_cache. It is just
used when new kmem_cache is created, so it's very rare case. Therefore,
add unlikely macro to help compiler optimization.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use the two functions to simplify the code avoiding numerous explicit
checks coded checking for a certain node to be online.
Get rid of various repeated calculations of kmem_cache_node structures.
[akpm@linux-foundation.org: fix build]
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.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>
init_lock_keys is only called by __init kmem_cache_init_late
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit b1cb0982bd ("change the management method of free objects of
the slab") introduced a bug on slab leak detector
('/proc/slab_allocators'). This detector works like as following
decription.
1. traverse all objects on all the slabs.
2. determine whether it is active or not.
3. if active, print who allocate this object.
but that commit changed the way how to manage free objects, so the logic
determining whether it is active or not is also changed. In before, we
regard object in cpu caches as inactive one, but, with this commit, we
mistakenly regard object in cpu caches as active one.
This intoduces kernel oops if DEBUG_PAGEALLOC is enabled. If
DEBUG_PAGEALLOC is enabled, kernel_map_pages() is used to detect who
corrupt free memory in the slab. It unmaps page table mapping if object
is free and map it if object is active. When slab leak detector check
object in cpu caches, it mistakenly think this object active so try to
access object memory to retrieve caller of allocation. At this point,
page table mapping to this object doesn't exist, so oops occurs.
Following is oops message reported from Dave.
It blew up when something tried to read /proc/slab_allocators
(Just cat it, and you should see the oops below)
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in:
[snip...]
CPU: 1 PID: 9386 Comm: trinity-c33 Not tainted 3.14.0-rc5+ #131
task: ffff8801aa46e890 ti: ffff880076924000 task.ti: ffff880076924000
RIP: 0010:[<ffffffffaa1a8f4a>] [<ffffffffaa1a8f4a>] handle_slab+0x8a/0x180
RSP: 0018:ffff880076925de0 EFLAGS: 00010002
RAX: 0000000000001000 RBX: 0000000000000000 RCX: 000000005ce85ce7
RDX: ffffea00079be100 RSI: 0000000000001000 RDI: ffff880107458000
RBP: ffff880076925e18 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 000000000000000f R12: ffff8801e6f84000
R13: ffffea00079be100 R14: ffff880107458000 R15: ffff88022bb8d2c0
FS: 00007fb769e45740(0000) GS:ffff88024d040000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8801e6f84ff8 CR3: 00000000a22db000 CR4: 00000000001407e0
DR0: 0000000002695000 DR1: 0000000002695000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000070602
Call Trace:
leaks_show+0xce/0x240
seq_read+0x28e/0x490
proc_reg_read+0x3d/0x80
vfs_read+0x9b/0x160
SyS_read+0x58/0xb0
tracesys+0xd4/0xd9
Code: f5 00 00 00 0f 1f 44 00 00 48 63 c8 44 3b 0c 8a 0f 84 e3 00 00 00 83 c0 01 44 39 c0 72 eb 41 f6 47 1a 01 0f 84 e9 00 00 00 89 f0 <4d> 8b 4c 04 f8 4d 85 c9 0f 84 88 00 00 00 49 8b 7e 08 4d 8d 46
RIP handle_slab+0x8a/0x180
To fix the problem, I introduce an object status buffer on each slab.
With this, we can track object status precisely, so slab leak detector
would not access active object and no kernel oops would occur. Memory
overhead caused by this fix is only imposed to CONFIG_DEBUG_SLAB_LEAK
which is mainly used for debugging, so memory overhead isn't big
problem.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reported-by: Dave Jones <davej@redhat.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently we have two pairs of kmemcg-related functions that are called on
slab alloc/free. The first is memcg_{bind,release}_pages that count the
total number of pages allocated on a kmem cache. The second is
memcg_{un}charge_slab that {un}charge slab pages to kmemcg resource
counter. Let's just merge them to keep the code clean.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When we create a sl[au]b cache, we allocate kmem_cache_node structures
for each online NUMA node. To handle nodes taken online/offline, we
register memory hotplug notifier and allocate/free kmem_cache_node
corresponding to the node that changes its state for each kmem cache.
To synchronize between the two paths we hold the slab_mutex during both
the cache creationg/destruction path and while tuning per-node parts of
kmem caches in memory hotplug handler, but that's not quite right,
because it does not guarantee that a newly created cache will have all
kmem_cache_nodes initialized in case it races with memory hotplug. For
instance, in case of slub:
CPU0 CPU1
---- ----
kmem_cache_create: online_pages:
__kmem_cache_create: slab_memory_callback:
slab_mem_going_online_callback:
lock slab_mutex
for each slab_caches list entry
allocate kmem_cache node
unlock slab_mutex
lock slab_mutex
init_kmem_cache_nodes:
for_each_node_state(node, N_NORMAL_MEMORY)
allocate kmem_cache node
add kmem_cache to slab_caches list
unlock slab_mutex
online_pages (continued):
node_states_set_node
As a result we'll get a kmem cache with not all kmem_cache_nodes
allocated.
To avoid issues like that we should hold get/put_online_mems() during
the whole kmem cache creation/destruction/shrink paths, just like we
deal with cpu hotplug. This patch does the trick.
Note, that after it's applied, there is no need in taking the slab_mutex
for kmem_cache_shrink any more, so it is removed from there.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have only a few places where we actually want to charge kmem so
instead of intruding into the general page allocation path with
__GFP_KMEMCG it's better to explictly charge kmem there. All kmem
charges will be easier to follow that way.
This is a step towards removing __GFP_KMEMCG. It removes __GFP_KMEMCG
from memcg caches' allocflags. Instead it makes slab allocation path
call memcg_charge_kmem directly getting memcg to charge from the cache's
memcg params.
This also eliminates any possibility of misaccounting an allocation
going from one memcg's cache to another memcg, because now we always
charge slabs against the memcg the cache belongs to. That's why this
patch removes the big comment to memcg_kmem_get_cache.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When the slab or slub allocators cannot allocate additional slab pages,
they emit diagnostic information to the kernel log such as current
number of slabs, number of objects, active objects, etc. This is always
coupled with a page allocation failure warning since it is controlled by
!__GFP_NOWARN.
Suppress this out of memory warning if the allocator is configured
without debug supported. The page allocation failure warning will
indicate it is a failed slab allocation, the order, and the gfp mask, so
this is only useful to diagnose allocator issues.
Since CONFIG_SLUB_DEBUG is already enabled by default for the slub
allocator, there is no functional change with this patch. If debug is
disabled, however, the warnings are now suppressed.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kirill A. Shutemov