The optimistic fast path may use cpuset_current_mems_allowed instead of
of a NULL nodemask supplied by the caller for cpuset allocations. The
preferred zone is calculated on this basis for statistic purposes and as
a starting point in the zonelist iterator.
However, if the context can ignore memory policies due to being atomic
or being able to ignore watermarks then the starting point in the
zonelist iterator is no longer correct. This patch resets the zonelist
iterator in the allocator slowpath if the context can ignore memory
policies. This will alter the zone used for statistics but only after
it is known that it makes sense for that context. Resetting it before
entering the slowpath would potentially allow an ALLOC_CPUSET allocation
to be accounted for against the wrong zone. Note that while nodemask is
not explicitly set to the original nodemask, it would only have been
overwritten if cpuset_enabled() and it was reset before the slowpath was
entered.
Link: http://lkml.kernel.org/r/20160602103936.GU2527@techsingularity.net
Fixes: c33d6c06f6 ("mm, page_alloc: avoid looking up the first zone in a zonelist twice")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
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>
Geert Uytterhoeven reported the following problem that bisected to
commit c33d6c06f6 ("mm, page_alloc: avoid looking up the first zone
in a zonelist twice") on m68k/ARAnyM
BUG: scheduling while atomic: cron/668/0x10c9a0c0
Modules linked in:
CPU: 0 PID: 668 Comm: cron Not tainted 4.6.0-atari-05133-gc33d6c06f60f710f #364
Call Trace: [<0003d7d0>] __schedule_bug+0x40/0x54
__schedule+0x312/0x388
__schedule+0x0/0x388
prepare_to_wait+0x0/0x52
schedule+0x64/0x82
schedule_timeout+0xda/0x104
set_next_entity+0x18/0x40
pick_next_task_fair+0x78/0xda
io_schedule_timeout+0x36/0x4a
bit_wait_io+0x0/0x40
bit_wait_io+0x12/0x40
__wait_on_bit+0x46/0x76
wait_on_page_bit_killable+0x64/0x6c
bit_wait_io+0x0/0x40
wake_bit_function+0x0/0x4e
__lock_page_or_retry+0xde/0x124
do_scan_async+0x114/0x17c
lookup_swap_cache+0x24/0x4e
handle_mm_fault+0x626/0x7de
find_vma+0x0/0x66
down_read+0x0/0xe
wait_on_page_bit_killable_timeout+0x77/0x7c
find_vma+0x16/0x66
do_page_fault+0xe6/0x23a
res_func+0xa3c/0x141a
buserr_c+0x190/0x6d4
res_func+0xa3c/0x141a
buserr+0x20/0x28
res_func+0xa3c/0x141a
buserr+0x20/0x28
The relationship is not obvious but it's due to a failure to rescan the
full zonelist after the fair zone allocation policy exhausts the batch
count. While this is a functional problem, it's also a performance
issue. A page allocator microbenchmark showed the following
4.7.0-rc1 4.7.0-rc1
vanilla reset-v1r2
Min alloc-odr0-1 327.00 ( 0.00%) 326.00 ( 0.31%)
Min alloc-odr0-2 235.00 ( 0.00%) 235.00 ( 0.00%)
Min alloc-odr0-4 198.00 ( 0.00%) 198.00 ( 0.00%)
Min alloc-odr0-8 170.00 ( 0.00%) 170.00 ( 0.00%)
Min alloc-odr0-16 156.00 ( 0.00%) 156.00 ( 0.00%)
Min alloc-odr0-32 150.00 ( 0.00%) 150.00 ( 0.00%)
Min alloc-odr0-64 146.00 ( 0.00%) 146.00 ( 0.00%)
Min alloc-odr0-128 145.00 ( 0.00%) 145.00 ( 0.00%)
Min alloc-odr0-256 155.00 ( 0.00%) 155.00 ( 0.00%)
Min alloc-odr0-512 168.00 ( 0.00%) 165.00 ( 1.79%)
Min alloc-odr0-1024 175.00 ( 0.00%) 174.00 ( 0.57%)
Min alloc-odr0-2048 180.00 ( 0.00%) 180.00 ( 0.00%)
Min alloc-odr0-4096 187.00 ( 0.00%) 186.00 ( 0.53%)
Min alloc-odr0-8192 190.00 ( 0.00%) 190.00 ( 0.00%)
Min alloc-odr0-16384 191.00 ( 0.00%) 191.00 ( 0.00%)
Min alloc-odr1-1 736.00 ( 0.00%) 445.00 ( 39.54%)
Min alloc-odr1-2 343.00 ( 0.00%) 335.00 ( 2.33%)
Min alloc-odr1-4 277.00 ( 0.00%) 270.00 ( 2.53%)
Min alloc-odr1-8 238.00 ( 0.00%) 233.00 ( 2.10%)
Min alloc-odr1-16 224.00 ( 0.00%) 218.00 ( 2.68%)
Min alloc-odr1-32 210.00 ( 0.00%) 208.00 ( 0.95%)
Min alloc-odr1-64 207.00 ( 0.00%) 203.00 ( 1.93%)
Min alloc-odr1-128 276.00 ( 0.00%) 202.00 ( 26.81%)
Min alloc-odr1-256 206.00 ( 0.00%) 202.00 ( 1.94%)
Min alloc-odr1-512 207.00 ( 0.00%) 202.00 ( 2.42%)
Min alloc-odr1-1024 208.00 ( 0.00%) 205.00 ( 1.44%)
Min alloc-odr1-2048 213.00 ( 0.00%) 212.00 ( 0.47%)
Min alloc-odr1-4096 218.00 ( 0.00%) 216.00 ( 0.92%)
Min alloc-odr1-8192 341.00 ( 0.00%) 219.00 ( 35.78%)
Note that order-0 allocations are unaffected but higher orders get a
small boost from this patch and a large reduction in system CPU usage
overall as can be seen here:
4.7.0-rc1 4.7.0-rc1
vanilla reset-v1r2
User 85.32 86.31
System 2221.39 2053.36
Elapsed 2368.89 2202.47
Fixes: c33d6c06f6 ("mm, page_alloc: avoid looking up the first zone in a zonelist twice")
Link: http://lkml.kernel.org/r/20160531100848.GR2527@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In DEBUG_VM kernel, we can hit infinite loop for order == 0 in
buffered_rmqueue() when check_new_pcp() returns 1, because the bad page
is never removed from the pcp list. Fix this by removing the page
before retrying. Also we don't need to check if page is non-NULL,
because we simply grab it from the list which was just tested for being
non-empty.
Fixes: 479f854a20 ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
Link: http://lkml.kernel.org/r/20160530090154.GM2527@techsingularity.net
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Per the discussion with Joonsoo Kim [1], we need check the return value
of lookup_page_ext() for all call sites since it might return NULL in
some cases, although it is unlikely, i.e. memory hotplug.
Tested with ltp with "page_owner=0".
[1] http://lkml.kernel.org/r/20160519002809.GA10245@js1304-P5Q-DELUXE
[akpm@linux-foundation.org: fix build-breaking typos]
[arnd@arndb.de: fix build problems from lookup_page_ext]
Link: http://lkml.kernel.org/r/6285269.2CksypHdYp@wuerfel
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1464023768-31025-1-git-send-email-yang.shi@linaro.org
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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 check page->flags twice for "HWPoisoned" case of
check_new_page_bad(), which can cause a race with unpoisoning.
This race unnecessarily taints kernel with "BUG: Bad page state".
check_new_page_bad() is the only caller of bad_page() which is
interested in __PG_HWPOISON, so let's move the hwpoison related code in
bad_page() to it.
Link: http://lkml.kernel.org/r/20160518100949.GA17299@hori1.linux.bs1.fc.nec.co.jp
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When CONFIG_PAGE_POISONING and CONFIG_KASAN is enabled,
free_pages_prepare()'s codeflow is below.
1)kmemcheck_free_shadow()
2)kasan_free_pages()
- set shadow byte of page is freed
3)kernel_poison_pages()
3.1) check access to page is valid or not using kasan
---> error occur, kasan think it is invalid access
3.2) poison page
4)kernel_map_pages()
So kasan_free_pages() should be called after poisoning the page.
Link: http://lkml.kernel.org/r/1463220405-7455-1-git-send-email-iamyooon@gmail.com
Signed-off-by: seokhoon.yoon <iamyooon@gmail.com>
Cc: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 92923ca3aa ("mm: meminit: only set page reserved in the
memblock region") the reserved bit is set on reserved memblock regions.
However start and end address are passed as unsigned long. This is only
32bit on i386, so it can end up marking the wrong pages reserved for
ranges at 4GB and above.
This was observed on a 32bit Xen dom0 which was booted with initial
memory set to a value below 4G but allowing to balloon in memory
(dom0_mem=1024M for example). This would define a reserved bootmem
region for the additional memory (for example on a 8GB system there was
a reverved region covering the 4GB-8GB range). But since the addresses
were passed on as unsigned long, this was actually marking all pages
from 0 to 4GB as reserved.
Fixes: 92923ca3aa ("mm: meminit: only set page reserved in the memblock region")
Link: http://lkml.kernel.org/r/1463491221-10573-1-git-send-email-stefan.bader@canonical.com
Signed-off-by: Stefan Bader <stefan.bader@canonical.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>
It's more convenient to use existing function helper to convert string
"on/off" to boolean.
Link: http://lkml.kernel.org/r/1461908824-16129-1-git-send-email-mnghuan@gmail.com
Signed-off-by: Minfei Huang <mnghuan@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Joonsoo has reported that he is able to trigger OOM for !costly high
order requests (heavy fork() workload close the OOM) with the new oom
detection rework. This is because we rely only on should_reclaim_retry
when the compaction is disabled and it only checks watermarks for the
requested order and so we might trigger OOM when there is a lot of free
memory.
It is not very clear what are the usual workloads when the compaction is
disabled. Relying on high order allocations heavily without any
mechanism to create those orders except for unbound amount of reclaim is
certainly not a good idea.
To prevent from potential regressions let's help this configuration
some. We have to sacrifice the determinsm though because there simply
is none here possible. should_compact_retry implementation for
!CONFIG_COMPACTION, which was empty so far, will do watermark check for
order-0 on all eligible zones. This will cause retrying until either
the reclaim cannot make any further progress or all the zones are
depleted even for order-0 pages. This means that the number of retries
is basically unbounded for !costly orders but that was the case before
the rework as well so this shouldn't regress.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1463051677-29418-3-git-send-email-mhocko@kernel.org
Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
"mm: consider compaction feedback also for costly allocation" has
removed the upper bound for the reclaim/compaction retries based on the
number of reclaimed pages for costly orders. While this is desirable
the patch did miss a mis interaction between reclaim, compaction and the
retry logic. The direct reclaim tries to get zones over min watermark
while compaction backs off and returns COMPACT_SKIPPED when all zones
are below low watermark + 1<<order gap. If we are getting really close
to OOM then __compaction_suitable can keep returning COMPACT_SKIPPED a
high order request (e.g. hugetlb order-9) while the reclaim is not able
to release enough pages to get us over low watermark. The reclaim is
still able to make some progress (usually trashing over few remaining
pages) so we are not able to break out from the loop.
I have seen this happening with the same test described in "mm: consider
compaction feedback also for costly allocation" on a swapless system.
The original problem got resolved by "vmscan: consider classzone_idx in
compaction_ready" but it shows how things might go wrong when we
approach the oom event horizont.
The reason why compaction requires being over low rather than min
watermark is not clear to me. This check was there essentially since
56de7263fc ("mm: compaction: direct compact when a high-order
allocation fails"). It is clearly an implementation detail though and
we shouldn't pull it into the generic retry logic while we should be
able to cope with such eventuality. The only place in
should_compact_retry where we retry without any upper bound is for
compaction_withdrawn() case.
Introduce compaction_zonelist_suitable function which checks the given
zonelist and returns true only if there is at least one zone which would
would unblock __compaction_suitable if more memory got reclaimed. In
this implementation it checks __compaction_suitable with NR_FREE_PAGES
plus part of the reclaimable memory as the target for the watermark
check. The reclaimable memory is reduced linearly by the allocation
order. The idea is that we do not want to reclaim all the remaining
memory for a single allocation request just unblock
__compaction_suitable which doesn't guarantee we will make a further
progress.
The new helper is then used if compaction_withdrawn() feedback was
provided so we do not retry if there is no outlook for a further
progress. !costly requests shouldn't be affected much - e.g. order-2
pages would require to have at least 64kB on the reclaimable LRUs while
order-9 would need at least 32M which should be enough to not lock up.
[vbabka@suse.cz: fix classzone_idx vs. high_zoneidx usage in compaction_zonelist_suitable]
[akpm@linux-foundation.org: fix it for Mel's mm-page_alloc-remove-field-from-alloc_context.patch]
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
PAGE_ALLOC_COSTLY_ORDER retry logic is mostly handled inside
should_reclaim_retry currently where we decide to not retry after at
least order worth of pages were reclaimed or the watermark check for at
least one zone would succeed after reclaiming all pages if the reclaim
hasn't made any progress. Compaction feedback is mostly ignored and we
just try to make sure that the compaction did at least something before
giving up.
The first condition was added by a41f24ea9f ("page allocator: smarter
retry of costly-order allocations) and it assumed that lumpy reclaim
could have created a page of the sufficient order. Lumpy reclaim, has
been removed quite some time ago so the assumption doesn't hold anymore.
Remove the check for the number of reclaimed pages and rely on the
compaction feedback solely. should_reclaim_retry now only makes sure
that we keep retrying reclaim for high order pages only if they are
hidden by watermaks so order-0 reclaim makes really sense.
should_compact_retry now keeps retrying even for the costly allocations.
The number of retries is reduced wrt. !costly requests because they are
less important and harder to grant and so their pressure shouldn't cause
contention for other requests or cause an over reclaim. We also do not
reset no_progress_loops for costly request to make sure we do not keep
reclaiming too agressively.
This has been tested by running a process which fragments memory:
- compact memory
- mmap large portion of the memory (1920M on 2GRAM machine with 2G
of swapspace)
- MADV_DONTNEED single page in PAGE_SIZE*((1UL<<MAX_ORDER)-1)
steps until certain amount of memory is freed (250M in my test)
and reduce the step to (step / 2) + 1 after reaching the end of
the mapping
- then run a script which populates the page cache 2G (MemTotal)
from /dev/zero to a new file
And then tries to allocate
nr_hugepages=$(awk '/MemAvailable/{printf "%d\n", $2/(2*1024)}' /proc/meminfo)
huge pages.
root@test1:~# echo 1 > /proc/sys/vm/overcommit_memory;echo 1 > /proc/sys/vm/compact_memory; ./fragment-mem-and-run /root/alloc_hugepages.sh 1920M 250M
Node 0, zone DMA 31 28 31 10 2 0 2 1 2 3 1
Node 0, zone DMA32 437 319 171 50 28 25 20 16 16 14 437
* This is the /proc/buddyinfo after the compaction
Done fragmenting. size=2013265920 freed=262144000
Node 0, zone DMA 165 48 3 1 2 0 2 2 2 2 0
Node 0, zone DMA32 35109 14575 185 51 41 12 6 0 0 0 0
* /proc/buddyinfo after memory got fragmented
Executing "/root/alloc_hugepages.sh"
Eating some pagecache
508623+0 records in
508623+0 records out
2083319808 bytes (2.1 GB) copied, 11.7292 s, 178 MB/s
Node 0, zone DMA 3 5 3 1 2 0 2 2 2 2 0
Node 0, zone DMA32 111 344 153 20 24 10 3 0 0 0 0
* /proc/buddyinfo after page cache got eaten
Trying to allocate 129
129
* 129 hugepages requested and all of them granted.
Node 0, zone DMA 3 5 3 1 2 0 2 2 2 2 0
Node 0, zone DMA32 127 97 30 99 11 6 2 1 4 0 0
* /proc/buddyinfo after hugetlb allocation.
10 runs will behave as follows:
Trying to allocate 130
130
--
Trying to allocate 129
129
--
Trying to allocate 128
128
--
Trying to allocate 129
129
--
Trying to allocate 128
128
--
Trying to allocate 129
129
--
Trying to allocate 132
132
--
Trying to allocate 129
129
--
Trying to allocate 128
128
--
Trying to allocate 129
129
So basically 100% success for all 10 attempts.
Without the patch numbers looked much worse:
Trying to allocate 128
12
--
Trying to allocate 129
14
--
Trying to allocate 129
7
--
Trying to allocate 129
16
--
Trying to allocate 129
30
--
Trying to allocate 129
38
--
Trying to allocate 129
19
--
Trying to allocate 129
37
--
Trying to allocate 129
28
--
Trying to allocate 129
37
Just for completness the base kernel without oom detection rework looks
as follows:
Trying to allocate 127
30
--
Trying to allocate 129
12
--
Trying to allocate 129
52
--
Trying to allocate 128
32
--
Trying to allocate 129
12
--
Trying to allocate 129
10
--
Trying to allocate 129
32
--
Trying to allocate 128
14
--
Trying to allocate 128
16
--
Trying to allocate 129
8
As we can see the success rate is much more volatile and smaller without
this patch. So the patch not only makes the retry logic for costly
requests more sensible the success rate is even higher.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
should_reclaim_retry will give up retries for higher order allocations
if none of the eligible zones has any requested or higher order pages
available even if we pass the watermak check for order-0. This is done
because there is no guarantee that the reclaimable and currently free
pages will form the required order.
This can, however, lead to situations where the high-order request (e.g.
order-2 required for the stack allocation during fork) will trigger OOM
too early - e.g. after the first reclaim/compaction round. Such a
system would have to be highly fragmented and there is no guarantee
further reclaim/compaction attempts would help but at least make sure
that the compaction was active before we go OOM and keep retrying even
if should_reclaim_retry tells us to oom if
- the last compaction round backed off or
- we haven't completed at least MAX_COMPACT_RETRIES active
compaction rounds.
The first rule ensures that the very last attempt for compaction was not
ignored while the second guarantees that the compaction has done some
work. Multiple retries might be needed to prevent occasional pigggy
backing of other contexts to steal the compacted pages before the
current context manages to retry to allocate them.
compaction_failed() is taken as a final word from the compaction that
the retry doesn't make much sense. We have to be careful though because
the first compaction round is MIGRATE_ASYNC which is rather weak as it
ignores pages under writeback and gives up too easily in other
situations. We therefore have to make sure that MIGRATE_SYNC_LIGHT mode
has been used before we give up. With this logic in place we do not
have to increase the migration mode unconditionally and rather do it
only if the compaction failed for the weaker mode. A nice side effect
is that the stronger migration mode is used only when really needed so
this has a potential of smaller latencies in some cases.
Please note that the compaction doesn't tell us much about how
successful it was when returning compaction_made_progress so we just
have to blindly trust that another retry is worthwhile and cap the
number to something reasonable to guarantee a convergence.
If the given number of successful retries is not sufficient for a
reasonable workloads we should focus on the collected compaction
tracepoints data and try to address the issue in the compaction code.
If this is not feasible we can increase the retries limit.
[mhocko@suse.com: fix warning]
Link: http://lkml.kernel.org/r/20160512061636.GA4200@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
wait_iff_congested has been used to throttle allocator before it retried
another round of direct reclaim to allow the writeback to make some
progress and prevent reclaim from looping over dirty/writeback pages
without making any progress.
We used to do congestion_wait before commit 0e093d9976 ("writeback: do
not sleep on the congestion queue if there are no congested BDIs or if
significant congestion is not being encountered in the current zone")
but that led to undesirable stalls and sleeping for the full timeout
even when the BDI wasn't congested. Hence wait_iff_congested was used
instead.
But it seems that even wait_iff_congested doesn't work as expected. We
might have a small file LRU list with all pages dirty/writeback and yet
the bdi is not congested so this is just a cond_resched in the end and
can end up triggering pre mature OOM.
This patch replaces the unconditional wait_iff_congested by
congestion_wait which is executed only if we _know_ that the last round
of direct reclaim didn't make any progress and dirty+writeback pages are
more than a half of the reclaimable pages on the zone which might be
usable for our target allocation. This shouldn't reintroduce stalls
fixed by 0e093d9976 because congestion_wait is called only when we are
getting hopeless when sleeping is a better choice than OOM with many
pages under IO.
We have to preserve logic introduced by commit 373ccbe592 ("mm,
vmstat: allow WQ concurrency to discover memory reclaim doesn't make any
progress") into the __alloc_pages_slowpath now that wait_iff_congested
is not used anymore. As the only remaining user of wait_iff_congested
is shrink_inactive_list we can remove the WQ specific short sleep from
wait_iff_congested because the sleep is needed to be done only once in
the allocation retry cycle.
[mhocko@suse.com: high_zoneidx->ac_classzone_idx to evaluate memory reserves properly]
Link: http://lkml.kernel.org/r/1463051677-29418-2-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__alloc_pages_slowpath has traditionally relied on the direct reclaim
and did_some_progress as an indicator that it makes sense to retry
allocation rather than declaring OOM. shrink_zones had to rely on
zone_reclaimable if shrink_zone didn't make any progress to prevent from
a premature OOM killer invocation - the LRU might be full of dirty or
writeback pages and direct reclaim cannot clean those up.
zone_reclaimable allows to rescan the reclaimable lists several times
and restart if a page is freed. This is really subtle behavior and it
might lead to a livelock when a single freed page keeps allocator
looping but the current task will not be able to allocate that single
page. OOM killer would be more appropriate than looping without any
progress for unbounded amount of time.
This patch changes OOM detection logic and pulls it out from shrink_zone
which is too low to be appropriate for any high level decisions such as
OOM which is per zonelist property. It is __alloc_pages_slowpath which
knows how many attempts have been done and what was the progress so far
therefore it is more appropriate to implement this logic.
The new heuristic is implemented in should_reclaim_retry helper called
from __alloc_pages_slowpath. It tries to be more deterministic and
easier to follow. It builds on an assumption that retrying makes sense
only if the currently reclaimable memory + free pages would allow the
current allocation request to succeed (as per __zone_watermark_ok) at
least for one zone in the usable zonelist.
This alone wouldn't be sufficient, though, because the writeback might
get stuck and reclaimable pages might be pinned for a really long time
or even depend on the current allocation context. Therefore there is a
backoff mechanism implemented which reduces the reclaim target after
each reclaim round without any progress. This means that we should
eventually converge to only NR_FREE_PAGES as the target and fail on the
wmark check and proceed to OOM. The backoff is simple and linear with
1/16 of the reclaimable pages for each round without any progress. We
are optimistic and reset counter for successful reclaim rounds.
Costly high order pages mostly preserve their semantic and those without
__GFP_REPEAT fail right away while those which have the flag set will
back off after the amount of reclaimable pages reaches equivalent of the
requested order. The only difference is that if there was no progress
during the reclaim we rely on zone watermark check. This is more
logical thing to do than previous 1<<order attempts which were a result
of zone_reclaimable faking the progress.
[vdavydov@virtuozzo.com: check classzone_idx for shrink_zone]
[hannes@cmpxchg.org: separate the heuristic into should_reclaim_retry]
[rientjes@google.com: use zone_page_state_snapshot for NR_FREE_PAGES]
[rientjes@google.com: shrink_zones doesn't need to return anything]
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__alloc_pages_direct_compact communicates potential back off by two
variables:
- deferred_compaction tells that the compaction returned
COMPACT_DEFERRED
- contended_compaction is set when there is a contention on
zone->lock resp. zone->lru_lock locks
__alloc_pages_slowpath then backs of for THP allocation requests to
prevent from long stalls. This is rather messy and it would be much
cleaner to return a single compact result value and hide all the nasty
details into __alloc_pages_direct_compact.
This patch shouldn't introduce any functional changes.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Compaction code is doing weird dances between COMPACT_FOO -> int ->
unsigned long
But there doesn't seem to be any reason for that. All functions which
return/use one of those constants are not expecting any other value so it
really makes sense to define an enum for them and make it clear that no
other values are expected.
This is a pure cleanup and shouldn't introduce any functional changes.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The inactive file list should still be large enough to contain readahead
windows and freshly written file data, but it no longer is the only
source for detecting multiple accesses to file pages. The workingset
refault measurement code causes recently evicted file pages that get
accessed again after a shorter interval to be promoted directly to the
active list.
With that mechanism in place, we can afford to (on a larger system)
dedicate more memory to the active file list, so we can actually cache
more of the frequently used file pages in memory, and not have them
pushed out by streaming writes, once-used streaming file reads, etc.
This can help things like database workloads, where only half the page
cache can currently be used to cache the database working set. This
patch automatically increases that fraction on larger systems, using the
same ratio that has already been used for anonymous memory.
[hannes@cmpxchg.org: cgroup-awareness]
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Andres Freund <andres@anarazel.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The page allocator fast path uses either the requested nodemask or
cpuset_current_mems_allowed if cpusets are enabled. If the allocation
context allows watermarks to be ignored then it can also ignore memory
policies. However, on entering the allocator slowpath the nodemask may
still be cpuset_current_mems_allowed and the policies are enforced.
This patch resets the nodemask appropriately before entering the
slowpath.
Link: http://lkml.kernel.org/r/20160504143628.GU2858@techsingularity.net
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
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>
Bad pages should be rare so the code handling them doesn't need to be
inline for performance reasons. Put it to separate function which
returns void. This also assumes that the initial page_expected_state()
result will match the result of the thorough check, i.e. the page
doesn't become "good" in the meanwhile. This matches the same
expectations already in place in free_pages_check().
!DEBUG_VM bloat-o-meter:
add/remove: 1/0 grow/shrink: 0/1 up/down: 134/-274 (-140)
function old new delta
check_new_page_bad - 134 +134
get_page_from_freelist 3468 3194 -274
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
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 new free_pcp_prepare() function shares a lot of code with
free_pages_prepare(), which makes this a maintenance risk when some
future patch modifies only one of them. We should be able to achieve
the same effect (skipping free_pages_check() from !DEBUG_VM configs) by
adding a parameter to free_pages_prepare() and making it inline, so the
checks (and the order != 0 parts) are eliminated from the call from
free_pcp_prepare().
!DEBUG_VM: bloat-o-meter reports no difference, as my gcc was already
inlining free_pages_prepare() and the elimination seems to work as
expected
DEBUG_VM bloat-o-meter:
add/remove: 0/1 grow/shrink: 2/0 up/down: 1035/-778 (257)
function old new delta
__free_pages_ok 297 1060 +763
free_hot_cold_page 480 752 +272
free_pages_prepare 778 - -778
Here inlining didn't occur before, and added some code, but it's ok for
a debug option.
[akpm@linux-foundation.org: fix build]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Every page allocated checks a number of page fields for validity. This
catches corruption bugs of pages that are already freed but it is
expensive. This patch weakens the debugging check by checking PCP pages
only when the PCP lists are being refilled. All compound pages are
checked. This potentially avoids debugging checks entirely if the PCP
lists are never emptied and refilled so some corruption issues may be
missed. Full checking requires DEBUG_VM.
With the two deferred debugging patches applied, the impact to a page
allocator microbenchmark is
4.6.0-rc3 4.6.0-rc3
inline-v3r6 deferalloc-v3r7
Min alloc-odr0-1 344.00 ( 0.00%) 317.00 ( 7.85%)
Min alloc-odr0-2 248.00 ( 0.00%) 231.00 ( 6.85%)
Min alloc-odr0-4 209.00 ( 0.00%) 192.00 ( 8.13%)
Min alloc-odr0-8 181.00 ( 0.00%) 166.00 ( 8.29%)
Min alloc-odr0-16 168.00 ( 0.00%) 154.00 ( 8.33%)
Min alloc-odr0-32 161.00 ( 0.00%) 148.00 ( 8.07%)
Min alloc-odr0-64 158.00 ( 0.00%) 145.00 ( 8.23%)
Min alloc-odr0-128 156.00 ( 0.00%) 143.00 ( 8.33%)
Min alloc-odr0-256 168.00 ( 0.00%) 154.00 ( 8.33%)
Min alloc-odr0-512 178.00 ( 0.00%) 167.00 ( 6.18%)
Min alloc-odr0-1024 186.00 ( 0.00%) 174.00 ( 6.45%)
Min alloc-odr0-2048 192.00 ( 0.00%) 180.00 ( 6.25%)
Min alloc-odr0-4096 198.00 ( 0.00%) 184.00 ( 7.07%)
Min alloc-odr0-8192 200.00 ( 0.00%) 188.00 ( 6.00%)
Min alloc-odr0-16384 201.00 ( 0.00%) 188.00 ( 6.47%)
Min free-odr0-1 189.00 ( 0.00%) 180.00 ( 4.76%)
Min free-odr0-2 132.00 ( 0.00%) 126.00 ( 4.55%)
Min free-odr0-4 104.00 ( 0.00%) 99.00 ( 4.81%)
Min free-odr0-8 90.00 ( 0.00%) 85.00 ( 5.56%)
Min free-odr0-16 84.00 ( 0.00%) 80.00 ( 4.76%)
Min free-odr0-32 80.00 ( 0.00%) 76.00 ( 5.00%)
Min free-odr0-64 78.00 ( 0.00%) 74.00 ( 5.13%)
Min free-odr0-128 77.00 ( 0.00%) 73.00 ( 5.19%)
Min free-odr0-256 94.00 ( 0.00%) 91.00 ( 3.19%)
Min free-odr0-512 108.00 ( 0.00%) 112.00 ( -3.70%)
Min free-odr0-1024 115.00 ( 0.00%) 118.00 ( -2.61%)
Min free-odr0-2048 120.00 ( 0.00%) 125.00 ( -4.17%)
Min free-odr0-4096 123.00 ( 0.00%) 129.00 ( -4.88%)
Min free-odr0-8192 126.00 ( 0.00%) 130.00 ( -3.17%)
Min free-odr0-16384 126.00 ( 0.00%) 131.00 ( -3.97%)
Note that the free paths for large numbers of pages is impacted as the
debugging cost gets shifted into that path when the page data is no
longer necessarily cache-hot.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
Every page free checks a number of page fields for validity. This
catches premature frees and corruptions but it is also expensive. This
patch weakens the debugging check by checking PCP pages at the time they
are drained from the PCP list. This will trigger the bug but the site
that freed the corrupt page will be lost. To get the full context, a
kernel rebuild with DEBUG_VM is necessary.
[akpm@linux-foundation.org: fix build]
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
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>
An important function for cpusets is cpuset_node_allowed(), which
optimizes on the fact if there's a single root CPU set, it must be
trivially allowed. But the check "nr_cpusets() <= 1" doesn't use the
cpusets_enabled_key static key the right way where static keys eliminate
branching overhead with jump labels.
This patch converts it so that static key is used properly. It's also
switched to the new static key API and the checking functions are
converted to return bool instead of int. We also provide a new variant
__cpuset_zone_allowed() which expects that the static key check was
already done and they key was enabled. This is needed for
get_page_from_freelist() where we want to also avoid the relatively
slower check when ALLOC_CPUSET is not set in alloc_flags.
The impact on the page allocator microbenchmark is less than expected
but the cleanup in itself is worthwhile.
4.6.0-rc2 4.6.0-rc2
multcheck-v1r20 cpuset-v1r20
Min alloc-odr0-1 348.00 ( 0.00%) 348.00 ( 0.00%)
Min alloc-odr0-2 254.00 ( 0.00%) 254.00 ( 0.00%)
Min alloc-odr0-4 213.00 ( 0.00%) 213.00 ( 0.00%)
Min alloc-odr0-8 186.00 ( 0.00%) 183.00 ( 1.61%)
Min alloc-odr0-16 173.00 ( 0.00%) 171.00 ( 1.16%)
Min alloc-odr0-32 166.00 ( 0.00%) 163.00 ( 1.81%)
Min alloc-odr0-64 162.00 ( 0.00%) 159.00 ( 1.85%)
Min alloc-odr0-128 160.00 ( 0.00%) 157.00 ( 1.88%)
Min alloc-odr0-256 169.00 ( 0.00%) 166.00 ( 1.78%)
Min alloc-odr0-512 180.00 ( 0.00%) 180.00 ( 0.00%)
Min alloc-odr0-1024 188.00 ( 0.00%) 187.00 ( 0.53%)
Min alloc-odr0-2048 194.00 ( 0.00%) 193.00 ( 0.52%)
Min alloc-odr0-4096 199.00 ( 0.00%) 198.00 ( 0.50%)
Min alloc-odr0-8192 202.00 ( 0.00%) 201.00 ( 0.50%)
Min alloc-odr0-16384 203.00 ( 0.00%) 202.00 ( 0.49%)
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Zefan Li <lizefan@huawei.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>
The function call overhead of get_pfnblock_flags_mask() is measurable in
the page free paths. This patch uses an inlined version that is faster.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
The original count is never reused so it can be removed.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
Check without side-effects should be easier to maintain. It also
removes the duplicated cpupid and flags reset done in !DEBUG_VM variant
of both free_pcp_prepare() and then bulkfree_pcp_prepare(). Finally, it
enables the next patch.
It shouldn't result in new branches, thanks to inlining of the check.
!DEBUG_VM bloat-o-meter:
add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-27 (-27)
function old new delta
__free_pages_ok 748 739 -9
free_pcppages_bulk 1403 1385 -18
DEBUG_VM:
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-28 (-28)
function old new delta
free_pages_prepare 806 778 -28
This is also slightly faster because cpupid information is not set on
tail pages so we can avoid resets there.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Every page allocated or freed is checked for sanity to avoid corruptions
that are difficult to detect later. A bad page could be due to a number
of fields. Instead of using multiple branches, this patch combines
multiple fields into a single branch. A detailed check is only
necessary if that check fails.
4.6.0-rc2 4.6.0-rc2
initonce-v1r20 multcheck-v1r20
Min alloc-odr0-1 359.00 ( 0.00%) 348.00 ( 3.06%)
Min alloc-odr0-2 260.00 ( 0.00%) 254.00 ( 2.31%)
Min alloc-odr0-4 214.00 ( 0.00%) 213.00 ( 0.47%)
Min alloc-odr0-8 186.00 ( 0.00%) 186.00 ( 0.00%)
Min alloc-odr0-16 173.00 ( 0.00%) 173.00 ( 0.00%)
Min alloc-odr0-32 165.00 ( 0.00%) 166.00 ( -0.61%)
Min alloc-odr0-64 162.00 ( 0.00%) 162.00 ( 0.00%)
Min alloc-odr0-128 161.00 ( 0.00%) 160.00 ( 0.62%)
Min alloc-odr0-256 170.00 ( 0.00%) 169.00 ( 0.59%)
Min alloc-odr0-512 181.00 ( 0.00%) 180.00 ( 0.55%)
Min alloc-odr0-1024 190.00 ( 0.00%) 188.00 ( 1.05%)
Min alloc-odr0-2048 196.00 ( 0.00%) 194.00 ( 1.02%)
Min alloc-odr0-4096 202.00 ( 0.00%) 199.00 ( 1.49%)
Min alloc-odr0-8192 205.00 ( 0.00%) 202.00 ( 1.46%)
Min alloc-odr0-16384 205.00 ( 0.00%) 203.00 ( 0.98%)
Again, the benefit is marginal but avoiding excessive branches is
important. Ideally the paths would not have to check these conditions
at all but regrettably abandoning the tests would make use-after-free
bugs much harder to detect.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
The classzone_idx can be inferred from preferred_zoneref so remove the
unnecessary field and save stack space.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
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>
The allocator fast path looks up the first usable zone in a zonelist and
then get_page_from_freelist does the same job in the zonelist iterator.
This patch preserves the necessary information.
4.6.0-rc2 4.6.0-rc2
fastmark-v1r20 initonce-v1r20
Min alloc-odr0-1 364.00 ( 0.00%) 359.00 ( 1.37%)
Min alloc-odr0-2 262.00 ( 0.00%) 260.00 ( 0.76%)
Min alloc-odr0-4 214.00 ( 0.00%) 214.00 ( 0.00%)
Min alloc-odr0-8 186.00 ( 0.00%) 186.00 ( 0.00%)
Min alloc-odr0-16 173.00 ( 0.00%) 173.00 ( 0.00%)
Min alloc-odr0-32 165.00 ( 0.00%) 165.00 ( 0.00%)
Min alloc-odr0-64 161.00 ( 0.00%) 162.00 ( -0.62%)
Min alloc-odr0-128 159.00 ( 0.00%) 161.00 ( -1.26%)
Min alloc-odr0-256 168.00 ( 0.00%) 170.00 ( -1.19%)
Min alloc-odr0-512 180.00 ( 0.00%) 181.00 ( -0.56%)
Min alloc-odr0-1024 190.00 ( 0.00%) 190.00 ( 0.00%)
Min alloc-odr0-2048 196.00 ( 0.00%) 196.00 ( 0.00%)
Min alloc-odr0-4096 202.00 ( 0.00%) 202.00 ( 0.00%)
Min alloc-odr0-8192 206.00 ( 0.00%) 205.00 ( 0.49%)
Min alloc-odr0-16384 206.00 ( 0.00%) 205.00 ( 0.49%)
The benefit is negligible and the results are within the noise but each
cycle counts.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
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>
Watermarks have to be checked on every allocation including the number
of pages being allocated and whether reserves can be accessed. The
reserves only matter if memory is limited and the free_pages adjustment
only applies to high-order pages. This patch adds a shortcut for
order-0 pages that avoids numerous calculations if there is plenty of
free memory yielding the following performance difference in a page
allocator microbenchmark;
4.6.0-rc2 4.6.0-rc2
optfair-v1r20 fastmark-v1r20
Min alloc-odr0-1 380.00 ( 0.00%) 364.00 ( 4.21%)
Min alloc-odr0-2 273.00 ( 0.00%) 262.00 ( 4.03%)
Min alloc-odr0-4 227.00 ( 0.00%) 214.00 ( 5.73%)
Min alloc-odr0-8 196.00 ( 0.00%) 186.00 ( 5.10%)
Min alloc-odr0-16 183.00 ( 0.00%) 173.00 ( 5.46%)
Min alloc-odr0-32 173.00 ( 0.00%) 165.00 ( 4.62%)
Min alloc-odr0-64 169.00 ( 0.00%) 161.00 ( 4.73%)
Min alloc-odr0-128 169.00 ( 0.00%) 159.00 ( 5.92%)
Min alloc-odr0-256 180.00 ( 0.00%) 168.00 ( 6.67%)
Min alloc-odr0-512 190.00 ( 0.00%) 180.00 ( 5.26%)
Min alloc-odr0-1024 198.00 ( 0.00%) 190.00 ( 4.04%)
Min alloc-odr0-2048 204.00 ( 0.00%) 196.00 ( 3.92%)
Min alloc-odr0-4096 209.00 ( 0.00%) 202.00 ( 3.35%)
Min alloc-odr0-8192 213.00 ( 0.00%) 206.00 ( 3.29%)
Min alloc-odr0-16384 214.00 ( 0.00%) 206.00 ( 3.74%)
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
The fair zone allocation policy is not without cost but it can be
reduced slightly. This patch removes an unnecessary local variable,
checks the likely conditions of the fair zone policy first, uses a bool
instead of a flags check and falls through when a remote node is
encountered instead of doing a full restart. The benefit is marginal
but it's there
4.6.0-rc2 4.6.0-rc2
decstat-v1r20 optfair-v1r20
Min alloc-odr0-1 377.00 ( 0.00%) 380.00 ( -0.80%)
Min alloc-odr0-2 273.00 ( 0.00%) 273.00 ( 0.00%)
Min alloc-odr0-4 226.00 ( 0.00%) 227.00 ( -0.44%)
Min alloc-odr0-8 196.00 ( 0.00%) 196.00 ( 0.00%)
Min alloc-odr0-16 183.00 ( 0.00%) 183.00 ( 0.00%)
Min alloc-odr0-32 175.00 ( 0.00%) 173.00 ( 1.14%)
Min alloc-odr0-64 172.00 ( 0.00%) 169.00 ( 1.74%)
Min alloc-odr0-128 170.00 ( 0.00%) 169.00 ( 0.59%)
Min alloc-odr0-256 183.00 ( 0.00%) 180.00 ( 1.64%)
Min alloc-odr0-512 191.00 ( 0.00%) 190.00 ( 0.52%)
Min alloc-odr0-1024 199.00 ( 0.00%) 198.00 ( 0.50%)
Min alloc-odr0-2048 204.00 ( 0.00%) 204.00 ( 0.00%)
Min alloc-odr0-4096 210.00 ( 0.00%) 209.00 ( 0.48%)
Min alloc-odr0-8192 213.00 ( 0.00%) 213.00 ( 0.00%)
Min alloc-odr0-16384 214.00 ( 0.00%) 214.00 ( 0.00%)
The benefit is marginal at best but one of the most important benefits,
avoiding a second search when falling back to another node is not
triggered by this particular test so the benefit for some corner cases
is understated.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
The page allocator fast path checks page multiple times unnecessarily.
This patch avoids all the slowpath checks if the first allocation
attempt succeeds.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
When bulk freeing pages from the per-cpu lists the zone is checked for
isolated pageblocks on every release. This patch checks it once per
drain.
[mgorman@techsingularity.net: fix locking radce, per Vlastimil]
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
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>
__GFP_HARDWALL only has meaning in the context of cpusets but the fast
path always applies the flag on the first attempt. Move the
manipulations into the cpuset paths where they will be masked by a
static branch in the common case.
With the other micro-optimisations in this series combined, the impact
on a page allocator microbenchmark is
4.6.0-rc2 4.6.0-rc2
decstat-v1r20 micro-v1r20
Min alloc-odr0-1 381.00 ( 0.00%) 377.00 ( 1.05%)
Min alloc-odr0-2 275.00 ( 0.00%) 273.00 ( 0.73%)
Min alloc-odr0-4 229.00 ( 0.00%) 226.00 ( 1.31%)
Min alloc-odr0-8 199.00 ( 0.00%) 196.00 ( 1.51%)
Min alloc-odr0-16 186.00 ( 0.00%) 183.00 ( 1.61%)
Min alloc-odr0-32 179.00 ( 0.00%) 175.00 ( 2.23%)
Min alloc-odr0-64 174.00 ( 0.00%) 172.00 ( 1.15%)
Min alloc-odr0-128 172.00 ( 0.00%) 170.00 ( 1.16%)
Min alloc-odr0-256 181.00 ( 0.00%) 183.00 ( -1.10%)
Min alloc-odr0-512 193.00 ( 0.00%) 191.00 ( 1.04%)
Min alloc-odr0-1024 201.00 ( 0.00%) 199.00 ( 1.00%)
Min alloc-odr0-2048 206.00 ( 0.00%) 204.00 ( 0.97%)
Min alloc-odr0-4096 212.00 ( 0.00%) 210.00 ( 0.94%)
Min alloc-odr0-8192 215.00 ( 0.00%) 213.00 ( 0.93%)
Min alloc-odr0-16384 216.00 ( 0.00%) 214.00 ( 0.93%)
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
page is guaranteed to be set before it is read with or without the
initialisation.
[akpm@linux-foundation.org: fix warning]
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
zonelist here is a copy of a struct field that is used once. Ditch it.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
The number of zones skipped to a zone expiring its fair zone allocation
quota is irrelevant. Convert to bool.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
alloc_flags is a bitmask of flags but it is signed which does not
necessarily generate the best code depending on the compiler. Even
without an impact, it makes more sense that this be unsigned.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
Pageblocks have an associated bitmap to store migrate types and whether
the pageblock should be skipped during compaction. The bitmap may be
associated with a memory section or a zone but the zone is looked up
unconditionally. The compiler should optimise this away automatically
so this is a cosmetic patch only in many cases.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
The page allocator iterates through a zonelist for zones that match the
addressing limitations and nodemask of the caller but many allocations
will not be restricted. Despite this, there is always functional call
overhead which builds up.
This patch inlines the optimistic basic case and only calls the iterator
function for the complex case. A hindrance was the fact that
cpuset_current_mems_allowed is used in the fastpath as the allowed
nodemask even though all nodes are allowed on most systems. The patch
handles this by only considering cpuset_current_mems_allowed if a cpuset
exists. As well as being faster in the fast-path, this removes some
junk in the slowpath.
The performance difference on a page allocator microbenchmark is;
4.6.0-rc2 4.6.0-rc2
statinline-v1r20 optiter-v1r20
Min alloc-odr0-1 412.00 ( 0.00%) 382.00 ( 7.28%)
Min alloc-odr0-2 301.00 ( 0.00%) 282.00 ( 6.31%)
Min alloc-odr0-4 247.00 ( 0.00%) 233.00 ( 5.67%)
Min alloc-odr0-8 215.00 ( 0.00%) 203.00 ( 5.58%)
Min alloc-odr0-16 199.00 ( 0.00%) 188.00 ( 5.53%)
Min alloc-odr0-32 191.00 ( 0.00%) 182.00 ( 4.71%)
Min alloc-odr0-64 187.00 ( 0.00%) 177.00 ( 5.35%)
Min alloc-odr0-128 185.00 ( 0.00%) 175.00 ( 5.41%)
Min alloc-odr0-256 193.00 ( 0.00%) 184.00 ( 4.66%)
Min alloc-odr0-512 207.00 ( 0.00%) 197.00 ( 4.83%)
Min alloc-odr0-1024 213.00 ( 0.00%) 203.00 ( 4.69%)
Min alloc-odr0-2048 220.00 ( 0.00%) 209.00 ( 5.00%)
Min alloc-odr0-4096 226.00 ( 0.00%) 214.00 ( 5.31%)
Min alloc-odr0-8192 229.00 ( 0.00%) 218.00 ( 4.80%)
Min alloc-odr0-16384 229.00 ( 0.00%) 219.00 ( 4.37%)
perf indicated that next_zones_zonelist disappeared in the profile and
__next_zones_zonelist did not appear. This is expected as the
micro-benchmark would hit the inlined fast-path every time.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
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>
The PageAnon check always checks for compound_head but this is a
relatively expensive check if the caller already knows the page is a
head page. This patch creates a helper and uses it in the page free
path which only operates on head pages.
With this patch and "Only check PageCompound for high-order pages", the
performance difference on a page allocator microbenchmark is;
4.6.0-rc2 4.6.0-rc2
vanilla nocompound-v1r20
Min alloc-odr0-1 425.00 ( 0.00%) 417.00 ( 1.88%)
Min alloc-odr0-2 313.00 ( 0.00%) 308.00 ( 1.60%)
Min alloc-odr0-4 257.00 ( 0.00%) 253.00 ( 1.56%)
Min alloc-odr0-8 224.00 ( 0.00%) 221.00 ( 1.34%)
Min alloc-odr0-16 208.00 ( 0.00%) 205.00 ( 1.44%)
Min alloc-odr0-32 199.00 ( 0.00%) 199.00 ( 0.00%)
Min alloc-odr0-64 195.00 ( 0.00%) 193.00 ( 1.03%)
Min alloc-odr0-128 192.00 ( 0.00%) 191.00 ( 0.52%)
Min alloc-odr0-256 204.00 ( 0.00%) 200.00 ( 1.96%)
Min alloc-odr0-512 213.00 ( 0.00%) 212.00 ( 0.47%)
Min alloc-odr0-1024 219.00 ( 0.00%) 219.00 ( 0.00%)
Min alloc-odr0-2048 225.00 ( 0.00%) 225.00 ( 0.00%)
Min alloc-odr0-4096 230.00 ( 0.00%) 231.00 ( -0.43%)
Min alloc-odr0-8192 235.00 ( 0.00%) 234.00 ( 0.43%)
Min alloc-odr0-16384 235.00 ( 0.00%) 234.00 ( 0.43%)
Min free-odr0-1 215.00 ( 0.00%) 191.00 ( 11.16%)
Min free-odr0-2 152.00 ( 0.00%) 136.00 ( 10.53%)
Min free-odr0-4 119.00 ( 0.00%) 107.00 ( 10.08%)
Min free-odr0-8 106.00 ( 0.00%) 96.00 ( 9.43%)
Min free-odr0-16 97.00 ( 0.00%) 87.00 ( 10.31%)
Min free-odr0-32 91.00 ( 0.00%) 83.00 ( 8.79%)
Min free-odr0-64 89.00 ( 0.00%) 81.00 ( 8.99%)
Min free-odr0-128 88.00 ( 0.00%) 80.00 ( 9.09%)
Min free-odr0-256 106.00 ( 0.00%) 95.00 ( 10.38%)
Min free-odr0-512 116.00 ( 0.00%) 111.00 ( 4.31%)
Min free-odr0-1024 125.00 ( 0.00%) 118.00 ( 5.60%)
Min free-odr0-2048 133.00 ( 0.00%) 126.00 ( 5.26%)
Min free-odr0-4096 136.00 ( 0.00%) 130.00 ( 4.41%)
Min free-odr0-8192 138.00 ( 0.00%) 130.00 ( 5.80%)
Min free-odr0-16384 137.00 ( 0.00%) 130.00 ( 5.11%)
There is a sizable boost to the free allocator performance. While there
is an apparent boost on the allocation side, it's likely a co-incidence
or due to the patches slightly reducing cache footprint.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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>
__alloc_pages_may_oom is the central place to decide when the
out_of_memory should be invoked. This is a good approach for most
checks there because they are page allocator specific and the allocation
fails right after for all of them.
The notable exception is GFP_NOFS context which is faking
did_some_progress and keep the page allocator looping even though there
couldn't have been any progress from the OOM killer. This patch doesn't
change this behavior because we are not ready to allow those allocation
requests to fail yet (and maybe we will face the reality that we will
never manage to safely fail these request). Instead __GFP_FS check is
moved down to out_of_memory and prevent from OOM victim selection there.
There are two reasons for that
- OOM notifiers might release some memory even from this context
as none of the registered notifier seems to be FS related
- this might help a dying thread to get an access to memory
reserves and move on which will make the behavior more
consistent with the case when the task gets killed from a
different context.
Keep a comment in __alloc_pages_may_oom to make sure we do not forget
how GFP_NOFS is special and that we really want to do something about
it.
Note to the current oom_notifier users:
The observable difference for you is that oom notifiers cannot depend on
any fs locks because we could deadlock. Not that this would be allowed
today because that would just lockup machine in most of the cases and
ruling out the OOM killer along the way. Another difference is that
callbacks might be invoked sooner now because GFP_NOFS is a weaker
reclaim context and so there could be reclaimable memory which is just
not reachable now. That would require GFP_NOFS only loads which are
really rare and more importantly the observable result would be dropping
of reconstructible object and potential performance drop which is not
such a big deal when we are struggling to fulfill other important
allocation requests.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Raushaniya Maksudova <rmaksudova@parallels.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ZONE_MOVABLE could be treated as highmem so we need to consider it for
accurate statistics. And, in following patches, ZONE_CMA will be
introduced and it can be treated as highmem, too. So, instead of
manually adding stat of ZONE_MOVABLE, looping all zones and check
whether the zone is highmem or not and add stat of the zone which can be
treated as highmem.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a system thats node's pfns are overlapped as follows:
-----pfn-------->
N0 N1 N2 N0 N1 N2
Therefore, we need to care this overlapping when iterating pfn range.
mark_free_pages() iterates requested zone's pfn range and unset all
range's bitmap first. And then it marks freepages in a zone to the
bitmap. If there is an overlapping zone, above unset could clear
previous marked bit and reference to this bitmap in the future will
cause the problem. To prevent it, this patch adds a zone check in
mark_free_pages().
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__offline_isolated_pages() and test_pages_isolated() are used by memory
hotplug. These functions require that range is in a single zone but
there is no code to do this because memory hotplug checks it before
calling these functions. To avoid confusing future user of these
functions, this patch adds comments to them.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mel Gorman