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2016-05-20z3fold: the 3-fold allocator for compressed pagesVitaly Wool3-1/+804
This patch introduces z3fold, a special purpose allocator for storing compressed pages. It is designed to store up to three compressed pages per physical page. It is a ZBUD derivative which allows for higher compression ratio keeping the simplicity and determinism of its predecessor. This patch comes as a follow-up to the discussions at the Embedded Linux Conference in San-Diego related to the talk [1]. The outcome of these discussions was that it would be good to have a compressed page allocator as stable and deterministic as zbud with with higher compression ratio. To keep the determinism and simplicity, z3fold, just like zbud, always stores an integral number of compressed pages per page, but it can store up to 3 pages unlike zbud which can store at most 2. Therefore the compression ratio goes to around 2.6x while zbud's one is around 1.7x. The patch is based on the latest linux.git tree. This version has been updated after testing on various simulators (e.g. ARM Versatile Express, MIPS Malta, x86_64/Haswell) and basing on comments from Dan Streetman [3]. [1] https://openiotelc2016.sched.org/event/6DAC/swapping-and-embedded-compression-relieves-the-pressure-vitaly-wool-softprise-consulting-ou [2] https://lkml.org/lkml/2016/4/21/799 [3] https://lkml.org/lkml/2016/5/4/852 Link: http://lkml.kernel.org/r/20160509151753.ec3f9fda3c9898d31ff52a32@gmail.com Signed-off-by: Vitaly Wool <vitalywool@gmail.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm: thp: split_huge_pmd_address() comment improvementAndrea Arcangeli1-2/+4
Comment is partly wrong, this improves it by including the case of split_huge_pmd_address() called by try_to_unmap_one if TTU_SPLIT_HUGE_PMD is set. Link: http://lkml.kernel.org/r/1462547040-1737-4-git-send-email-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20vmstat: get rid of the ugly cpu_stat_off variableChristoph Lameter1-41/+10
The cpu_stat_off variable is unecessary since we can check if a workqueue request is pending otherwise. Removal of cpu_stat_off makes it pretty easy for the vmstat shepherd to ensure that the proper things happen. Removing the state also removes all races related to it. Should a workqueue not be scheduled as needed for vmstat_update then the shepherd will notice and schedule it as needed. Should a workqueue be unecessarily scheduled then the vmstat updater will disable it. [akpm@linux-foundation.org: fix indentation, per Michal] Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1605061306460.17934@east.gentwo.org Signed-off-by: Christoph Lameter <cl@linux.com> Cc: Tejun Heo <htejun@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20memcg: fix stale mem_cgroup_force_empty() commentGreg Thelen1-2/+1
Commit f61c42a7d911 ("memcg: remove tasks/children test from mem_cgroup_force_empty()") removed memory reparenting from the function. Fix the function's comment. Link: http://lkml.kernel.org/r/1462569810-54496-1-git-send-email-gthelen@google.com Signed-off-by: Greg Thelen <gthelen@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm: use existing helper to convert "on"/"off" to booleanMinfei Huang2-15/+2
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>
2016-05-20mm/swap.c: put activate_page_pvecs and other pagevecs togetherMing Li1-2/+3
Put the activate_page_pvecs definition next to those of the other pagevecs, for clarity. Signed-off-by: Ming Li <mingli199x@qq.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm, hugetlb_cgroup: round limit_in_bytes down to hugepage sizeDavid Rientjes1-9/+26
The page_counter rounds limits down to page size values. This makes sense, except in the case of hugetlb_cgroup where it's not possible to charge partial hugepages. If the hugetlb_cgroup margin is less than the hugepage size being charged, it will fail as expected. Round the hugetlb_cgroup limit down to hugepage size, since it is the effective limit of the cgroup. For consistency, round down PAGE_COUNTER_MAX as well when a hugetlb_cgroup is created: this prevents error reports when a user cannot restore the value to the kernel default. Signed-off-by: David Rientjes <rientjes@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Nikolay Borisov <kernel@kyup.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm: enable RLIMIT_DATA by default with workaround for valgrindKonstantin Khlebnikov1-4/+8
Since commit 84638335900f ("mm: rework virtual memory accounting") RLIMIT_DATA limits both brk() and private mmap() but this's disabled by default because of incompatibility with older versions of valgrind. Valgrind always set limit to zero and fails if RLIMIT_DATA is enabled. Fortunately it changes only rlim_cur and keeps rlim_max for reverting limit back when needed. This patch checks current usage also against rlim_max if rlim_cur is zero. This is safe because task anyway can increase rlim_cur up to rlim_max. Size of brk is still checked against rlim_cur, so this part is completely compatible - zero rlim_cur forbids brk() but allows private mmap(). Link: http://lkml.kernel.org/r/56A28613.5070104@de.ibm.com Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm: fix incorrect pfn passed to untrack_pfn() in remap_pfn_range()Yongji Xie1-2/+3
We use generic hooks in remap_pfn_range() to help archs to track pfnmap regions. The code is something like: int remap_pfn_range() { ... track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size)); ... pfn -= addr >> PAGE_SHIFT; ... untrack_pfn(vma, pfn, PAGE_ALIGN(size)); ... } Here we can easily find the pfn is changed but not recovered before untrack_pfn() is called. That's incorrect. There are no known runtime effects - this is from inspection. Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Matthew Wilcox <matthew.r.wilcox@intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm/vmalloc: keep a separate lazy-free listChris Wilson1-20/+19
When mixing lots of vmallocs and set_memory_*() (which calls vm_unmap_aliases()) I encountered situations where the performance degraded severely due to the walking of the entire vmap_area list each invocation. One simple improvement is to add the lazily freed vmap_area to a separate lockless free list, such that we then avoid having to walk the full list on each purge. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Roman Pen <r.peniaev@gmail.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Roman Pen <r.peniaev@gmail.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Toshi Kani <toshi.kani@hp.com> Cc: Shawn Lin <shawn.lin@rock-chips.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm/memblock.c: move memblock_{add,reserve}_region into memblock_{add,reserve}Alexander Kuleshov1-22/+6
memblock_add_region() and memblock_reserve_region() do nothing specific before the call of memblock_add_range(), only print debug output. We can do the same in memblock_add() and memblock_reserve() since both memblock_add_region() and memblock_reserve_region() are not used by anybody outside of memblock.c and memblock_{add,reserve}() have the same set of flags and nids. Since memblock_add_region() and memblock_reserve_region() will be inlined, there will not be functional changes, but will improve code readability a little. Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Pekka Enberg <penberg@kernel.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Tang Chen <tangchen@cn.fujitsu.com> Cc: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm/memory-failure.c: replace "MCE" with "Memory failure"Chen Yucong1-32/+40
HWPoison was specific to some particular x86 platforms. And it is often seen as high level machine check handler. And therefore, 'MCE' is used for the format prefix of printk(). However, 'PowerNV' has also used HWPoison for handling memory errors[1], so 'MCE' is no longer suitable to memory_failure.c. Additionally, 'MCE' and 'Memory failure' have different context. The former belongs to exception context and the latter belongs to process context. Furthermore, HWPoison can also be used for off-lining those sub-health pages that do not trigger any machine check exception. This patch aims to replace 'MCE' with a more appropriate prefix. [1] commit 75eb3d9b60c2 ("powerpc/powernv: Get FSP memory errors and plumb into memory poison infrastructure.") Signed-off-by: Chen Yucong <slaoub@gmail.com> Acked-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>
2016-05-20mm: thp: simplify the implementation of mk_huge_pmd()Yang Shi1-4/+1
The implementation of mk_huge_pmd looks verbose, it could be just simplified to one line code. Signed-off-by: Yang Shi <yang.shi@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm,oom: speed up select_bad_process() loopTetsuo Handa1-11/+6
Since commit 3a5dda7a17cf ("oom: prevent unnecessary oom kills or kernel panics"), select_bad_process() is using for_each_process_thread(). Since oom_unkillable_task() scans all threads in the caller's thread group and oom_task_origin() scans signal_struct of the caller's thread group, we don't need to call oom_unkillable_task() and oom_task_origin() on each thread. Also, since !mm test will be done later at oom_badness(), we don't need to do !mm test on each thread. Therefore, we only need to do TIF_MEMDIE test on each thread. Although the original code was correct it was quite inefficient because each thread group was scanned num_threads times which can be a lot especially with processes with many threads. Even though the OOM is extremely cold path it is always good to be as effective as possible when we are inside rcu_read_lock() - aka unpreemptible context. If we track number of TIF_MEMDIE threads inside signal_struct, we don't need to do TIF_MEMDIE test on each thread. This will allow select_bad_process() to use for_each_process(). This patch adds a counter to signal_struct for tracking how many TIF_MEMDIE threads are in a given thread group, and check it at oom_scan_process_thread() so that select_bad_process() can use for_each_process() rather than for_each_process_thread(). [mhocko@suse.com: do not blow the signal_struct size] Link: http://lkml.kernel.org/r/20160520075035.GF19172@dhcp22.suse.cz Link: http://lkml.kernel.org/r/201605182230.IDC73435.MVSOHLFOQFOJtF@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: Michal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.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>
2016-05-20mm, oom_reaper: do not mmput synchronously from the oom reaper contextMichal Hocko1-2/+6
Tetsuo has properly noted that mmput slow path might get blocked waiting for another party (e.g. exit_aio waits for an IO). If that happens the oom_reaper would be put out of the way and will not be able to process next oom victim. We should strive for making this context as reliable and independent on other subsystems as much as possible. Introduce mmput_async which will perform the slow path from an async (WQ) context. This will delay the operation but that shouldn't be a problem because the oom_reaper has reclaimed the victim's address space for most cases as much as possible and the remaining context shouldn't bind too much memory anymore. The only exception is when mmap_sem trylock has failed which shouldn't happen too often. The issue is only theoretical but not impossible. Signed-off-by: Michal Hocko <mhocko@suse.com> Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm, oom_reaper: hide oom reaped tasks from OOM killer more carefullyMichal Hocko1-2/+7
Commit 36324a990cf5 ("oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space") not only clears TIF_MEMDIE for oom reaped task but also set OOM_SCORE_ADJ_MIN for the target task to hide it from the oom killer. This works in simple cases but it is not sufficient for (unlikely) cases where the mm is shared between independent processes (as they do not share signal struct). If the mm had only small amount of memory which could be reaped then another task sharing the mm could be selected and that wouldn't help to move out from the oom situation. Introduce MMF_OOM_REAPED mm flag which is checked in oom_badness (same as OOM_SCORE_ADJ_MIN) and task is skipped if the flag is set. Set the flag after __oom_reap_task is done with a task. This will force the select_bad_process() to ignore all already oom reaped tasks as well as no such task is sacrificed for its parent. Signed-off-by: Michal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm, oom: protect !costly allocations some more for !CONFIG_COMPACTIONMichal Hocko1-0/+18
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>
2016-05-20mm, oom, compaction: prevent from should_compact_retry looping for ever for ↵Michal Hocko2-13/+52
costly orders "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 56de7263fcf3 ("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>
2016-05-20mm: consider compaction feedback also for costly allocationMichal Hocko1-31/+32
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 a41f24ea9fd6 ("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>
2016-05-20mm, oom: protect !costly allocations some moreMichal Hocko1-10/+78
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>
2016-05-20mm: throttle on IO only when there are too many dirty and writeback pagesMichal Hocko2-21/+40
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 0e093d99763e ("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 0e093d99763e 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 373ccbe59270 ("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>
2016-05-20mm, oom: rework oom detectionMichal Hocko2-29/+96
__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>
2016-05-20mm, compaction: simplify __alloc_pages_direct_compact feedback interfaceMichal Hocko1-36/+31
__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>
2016-05-20mm, compaction: distinguish between full and partial COMPACT_COMPLETEMichal Hocko2-3/+12
COMPACT_COMPLETE now means that compaction and free scanner met. This is not very useful information if somebody just wants to use this feedback and make any decisions based on that. The current caller might be a poor guy who just happened to scan tiny portion of the zone and that could be the reason no suitable pages were compacted. Make sure we distinguish the full and partial zone walks. Consumers should treat COMPACT_PARTIAL_SKIPPED as a potential success and be optimistic in retrying. The existing users of COMPACT_COMPLETE are conservatively changed to use COMPACT_PARTIAL_SKIPPED as well but some of them should be probably reconsidered and only defer the compaction only for COMPACT_COMPLETE with the new semantic. 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>
2016-05-20mm, compaction: distinguish COMPACT_DEFERRED from COMPACT_SKIPPEDMichal Hocko1-3/+5
try_to_compact_pages() can currently return COMPACT_SKIPPED even when the compaction is defered for some zone just because zone DMA is skipped in 99% of cases due to watermark checks. This makes COMPACT_DEFERRED basically unusable for the page allocator as a feedback mechanism. Make sure we distinguish those two states properly and switch their ordering in the enum. This would mean that the COMPACT_SKIPPED will be returned only when all eligible zones are skipped. As a result COMPACT_DEFERRED handling for THP in __alloc_pages_slowpath will be more precise and we would bail out rather than reclaim. 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>
2016-05-20mm, compaction: cover all compaction mode in compact_zoneMichal Hocko1-8/+5
The compiler is complaining after "mm, compaction: change COMPACT_ constants into enum" mm/compaction.c: In function `compact_zone': mm/compaction.c:1350:2: warning: enumeration value `COMPACT_DEFERRED' not handled in switch [-Wswitch] switch (ret) { ^ mm/compaction.c:1350:2: warning: enumeration value `COMPACT_COMPLETE' not handled in switch [-Wswitch] mm/compaction.c:1350:2: warning: enumeration value `COMPACT_NO_SUITABLE_PAGE' not handled in switch [-Wswitch] mm/compaction.c:1350:2: warning: enumeration value `COMPACT_NOT_SUITABLE_ZONE' not handled in switch [-Wswitch] mm/compaction.c:1350:2: warning: enumeration value `COMPACT_CONTENDED' not handled in switch [-Wswitch] compaction_suitable is allowed to return only COMPACT_PARTIAL, COMPACT_SKIPPED and COMPACT_CONTINUE so other cases are simply impossible. Put a VM_BUG_ON to catch an impossible return value. 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>
2016-05-20mm, compaction: change COMPACT_ constants into enumMichal Hocko2-14/+15
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>
2016-05-20vmscan: consider classzone_idx in compaction_readyMichal Hocko1-4/+4
Motivation: As pointed out by Linus [2][3] relying on zone_reclaimable as a way to communicate the reclaim progress is rater dubious. I tend to agree, not only it is really obscure, it is not hard to imagine cases where a single page freed in the loop keeps all the reclaimers looping without getting any progress because their gfp_mask wouldn't allow to get that page anyway (e.g. single GFP_ATOMIC alloc and free loop). This is rather rare so it doesn't happen in the practice but the current logic which we have is rather obscure and hard to follow a also non-deterministic. This is an attempt to make the OOM detection more deterministic and easier to follow because each reclaimer basically tracks its own progress which is implemented at the page allocator layer rather spread out between the allocator and the reclaim. The more on the implementation is described in the first patch. I have tested several different scenarios but it should be clear that testing OOM killer is quite hard to be representative. There is usually a tiny gap between almost OOM and full blown OOM which is often time sensitive. Anyway, I have tested the following 2 scenarios and I would appreciate if there are more to test. Testing environment: a virtual machine with 2G of RAM and 2CPUs without any swap to make the OOM more deterministic. 1) 2 writers (each doing dd with 4M blocks to an xfs partition with 1G file size, removes the files and starts over again) running in parallel for 10s to build up a lot of dirty pages when 100 parallel mem_eaters (anon private populated mmap which waits until it gets signal) with 80M each. This causes an OOM flood of course and I have compared both patched and unpatched kernels. The test is considered finished after there are no OOM conditions detected. This should tell us whether there are any excessive kills or some of them premature (e.g. due to dirty pages): I have performed two runs this time each after a fresh boot. * base kernel $ grep "Out of memory:" base-oom-run1.log | wc -l 78 $ grep "Out of memory:" base-oom-run2.log | wc -l 78 $ grep "Kill process" base-oom-run1.log | tail -n1 [ 91.391203] Out of memory: Kill process 3061 (mem_eater) score 39 or sacrifice child $ grep "Kill process" base-oom-run2.log | tail -n1 [ 82.141919] Out of memory: Kill process 3086 (mem_eater) score 39 or sacrifice child $ grep "DMA32 free:" base-oom-run1.log | sed 's@.*free:\([0-9]*\)kB.*@\1@' | calc_min_max.awk min: 5376.00 max: 6776.00 avg: 5530.75 std: 166.50 nr: 61 $ grep "DMA32 free:" base-oom-run2.log | sed 's@.*free:\([0-9]*\)kB.*@\1@' | calc_min_max.awk min: 5416.00 max: 5608.00 avg: 5514.15 std: 42.94 nr: 52 $ grep "DMA32.*all_unreclaimable? no" base-oom-run1.log | wc -l 1 $ grep "DMA32.*all_unreclaimable? no" base-oom-run2.log | wc -l 3 * patched kernel $ grep "Out of memory:" patched-oom-run1.log | wc -l 78 miso@tiehlicka /mnt/share/devel/miso/kvm $ grep "Out of memory:" patched-oom-run2.log | wc -l 77 e grep "Kill process" patched-oom-run1.log | tail -n1 [ 497.317732] Out of memory: Kill process 3108 (mem_eater) score 39 or sacrifice child $ grep "Kill process" patched-oom-run2.log | tail -n1 [ 316.169920] Out of memory: Kill process 3093 (mem_eater) score 39 or sacrifice child $ grep "DMA32 free:" patched-oom-run1.log | sed 's@.*free:\([0-9]*\)kB.*@\1@' | calc_min_max.awk min: 5420.00 max: 5808.00 avg: 5513.90 std: 60.45 nr: 78 $ grep "DMA32 free:" patched-oom-run2.log | sed 's@.*free:\([0-9]*\)kB.*@\1@' | calc_min_max.awk min: 5380.00 max: 6384.00 avg: 5520.94 std: 136.84 nr: 77 e grep "DMA32.*all_unreclaimable? no" patched-oom-run1.log | wc -l 2 $ grep "DMA32.*all_unreclaimable? no" patched-oom-run2.log | wc -l 3 The patched kernel run noticeably longer while invoking OOM killer same number of times. This means that the original implementation is much more aggressive and triggers the OOM killer sooner. free pages stats show that neither kernels went OOM too early most of the time, though. I guess the difference is in the backoff when retries without any progress do sleep for a while if there is memory under writeback or dirty which is highly likely considering the parallel IO. Both kernels have seen races where zone wasn't marked unreclaimable and we still hit the OOM killer. This is most likely a race where a task managed to exit between the last allocation attempt and the oom killer invocation. 2) 2 writers again with 10s of run and then 10 mem_eaters to consume as much memory as possible without triggering the OOM killer. This required a lot of tuning but I've considered 3 consecutive runs in three different boots without OOM as a success. * base kernel size=$(awk '/MemFree/{printf "%dK", ($2/10)-(16*1024)}' /proc/meminfo) * patched kernel size=$(awk '/MemFree/{printf "%dK", ($2/10)-(12*1024)}' /proc/meminfo) That means 40M more memory was usable without triggering OOM killer. The base kernel sometimes managed to handle the same as patched but it wasn't consistent and failed in at least on of the 3 runs. This seems like a minor improvement. I was testing also GPF_REPEAT costly requests (hughetlb) with fragmented memory and under memory pressure. The results are in patch 11 where the logic is implemented. In short I can see huge improvement there. I am certainly interested in other usecases as well as well as any feedback. Especially those which require higher order requests. This patch (of 14): While playing with the oom detection rework [1] I have noticed that my heavy order-9 (hugetlb) load close to OOM ended up in an endless loop where the reclaim hasn't made any progress but did_some_progress didn't reflect that and compaction_suitable was backing off because no zone is above low wmark + 1 << order. It turned out that this is in fact an old standing bug in compaction_ready which ignores the requested_highidx and did the watermark check for 0 classzone_idx. This succeeds for zone DMA most of the time as the zone is mostly unused because of lowmem protection. As a result costly high order allocatios always report a successfull progress even when there was none. This wasn't a problem so far because these allocations usually fail quite early or retry only few times with __GFP_REPEAT but this will change after later patch in this series so make sure to not lie about the progress and propagate requested_highidx down to compaction_ready and use it for both the watermak check and compaction_suitable to fix this issue. [1] http://lkml.kernel.org/r/1459855533-4600-1-git-send-email-mhocko@kernel.org [2] https://lkml.org/lkml/2015/10/12/808 [3] https://lkml.org/lkml/2015/10/13/597 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: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Joonsoo Kim <js1304@gmail.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20mm: vmscan: reduce size of inactive file listRik van Riel2-106/+42
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>
2016-05-20mm: filemap: only do access activations on readsJohannes Weiner1-1/+1
Andres observed that his database workload is struggling with the transaction journal creating pressure on frequently read pages. Access patterns like transaction journals frequently write the same pages over and over, but in the majority of cases those pages are never read back. There are no caching benefits to be had for those pages, so activating them and having them put pressure on pages that do benefit from caching is a bad choice. Leave page activations to read accesses and don't promote pages based on writes alone. It could be said that partially written pages do contain cache-worthy data, because even if *userspace* does not access the unwritten part, the kernel still has to read it from the filesystem for correctness. However, a counter argument is that these pages enjoy at least *some* protection over other inactive file pages through the writeback cache, in the sense that dirty pages are written back with a delay and cache reclaim leaves them alone until they have been written back to disk. Should that turn out to be insufficient and we see increased read IO from partial writes under memory pressure, we can always go back and update grab_cache_page_write_begin() to take (pos, len) so that it can tell partial writes from pages that don't need partial reads. But for now, keep it simple. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reported-by: Andres Freund <andres@anarazel.de> 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>
2016-05-20mm: workingset: only do workingset activations on readsRik van Riel1-1/+5
This is a follow-up to http://www.spinics.net/lists/linux-mm/msg101739.html where Andres reported his database workingset being pushed out by the minimum size enforcement of the inactive file list - currently 50% of cache - as well as repeatedly written file pages that are never actually read. Two changes fell out of the discussions. The first change observes that pages that are only ever written don't benefit from caching beyond what the writeback cache does for partial page writes, and so we shouldn't promote them to the active file list where they compete with pages whose cached data is actually accessed repeatedly. This change comes in two patches - one for in-cache write accesses and one for refaults triggered by writes, neither of which should promote a cache page. Second, with the refault detection we don't need to set 50% of the cache aside for used-once cache anymore since we can detect frequently used pages even when they are evicted between accesses. We can allow the active list to be bigger and thus protect a bigger workingset that isn't challenged by streamers. Depending on the access patterns, this can increase major faults during workingset transitions for better performance during stable phases. This patch (of 3): When rewriting a page, the data in that page is replaced with new data. This means that evicting something else from the active file list, in order to cache data that will be replaced by something else, is likely to be a waste of memory. It is better to save the active list for frequently read pages, because reads actually use the data that is in the page. This patch ignores partial writes, because it is unclear whether the complexity of identifying those is worth any potential performance gain obtained from better caching pages that see repeated partial writes at large enough intervals to not get caught by the use-twice promotion code used for the inactive file list. 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>
2016-05-19mm, page_alloc: restore the original nodemask if the fast path allocation failedMel Gorman1-0/+6
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>
2016-05-19mm, page_alloc: uninline the bad page part of check_new_page()Vlastimil Babka1-16/+17
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>
2016-05-19mm, page_alloc: don't duplicate code in free_pcp_prepareMel Gorman1-78/+55
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>
2016-05-19mm, page_alloc: defer debugging checks of pages allocated from the PCPMel Gorman1-28/+64
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>
2016-05-19mm, page_alloc: defer debugging checks of freed pages until a PCP drainMel Gorman1-51/+101
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>
2016-05-19cpuset: use static key better and convert to new APIVlastimil Babka1-1/+1
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>
2016-05-19mm, page_alloc: inline pageblock lookup in page free fast pathsMel Gorman3-90/+102
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>
2016-05-19mm, page_alloc: remove unnecessary variable from free_pcppages_bulkMel Gorman1-4/+3
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>
2016-05-19mm, page_alloc: pull out side effects from free_pages_checkMel Gorman1-5/+8
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>
2016-05-19mm, page_alloc: un-inline the bad part of free_pages_checkMel Gorman1-8/+13
From: Vlastimil Babka <vbabka@suse.cz> !DEBUG_VM size and bloat-o-meter: add/remove: 1/0 grow/shrink: 0/2 up/down: 124/-370 (-246) function old new delta free_pages_check_bad - 124 +124 free_pcppages_bulk 1288 1171 -117 __free_pages_ok 948 695 -253 DEBUG_VM: add/remove: 1/0 grow/shrink: 0/1 up/down: 124/-214 (-90) function old new delta free_pages_check_bad - 124 +124 free_pages_prepare 1112 898 -214 [akpm@linux-foundation.org: fix whitespace] 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>
2016-05-19mm, page_alloc: check multiple page fields with a single branchMel Gorman1-12/+43
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>
2016-05-19mm, page_alloc: remove field from alloc_contextMel Gorman3-8/+7
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>
2016-05-19mm, page_alloc: avoid looking up the first zone in a zonelist twiceMel Gorman3-28/+27
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>
2016-05-19mm, page_alloc: shortcut watermark checks for order-0 pagesMel Gorman1-1/+27
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>
2016-05-19mm, page_alloc: reduce cost of fair zone allocation policy retryMel Gorman1-18/+14
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>
2016-05-19mm, page_alloc: shorten the page allocator fast pathMel Gorman1-16/+17
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>
2016-05-19mm, page_alloc: check once if a zone has isolated pageblocksMel Gorman1-1/+3
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>
2016-05-19mm, page_alloc: move __GFP_HARDWALL modifications out of the fastpathMel Gorman1-3/+5
__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>
2016-05-19mm, page_alloc: remove unnecessary initialisation from __alloc_pages_nodemask()Mel Gorman1-2/+5
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>
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