1. 20 May, 2016 1 commit
  2. 19 May, 2016 3 commits
  3. 25 Mar, 2016 1 commit
    • Alexander Potapenko's avatar
      mm, kasan: add GFP flags to KASAN API · 505f5dcb
      Alexander Potapenko authored
      Add GFP flags to KASAN hooks for future patches to use.
      
      This patch is based on the "mm: kasan: unified support for SLUB and SLAB
      allocators" patch originally prepared by Dmitry Chernenkov.
      Signed-off-by: default avatarAlexander Potapenko <glider@google.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Andrey Konovalov <adech.fo@gmail.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Konstantin Serebryany <kcc@google.com>
      Cc: Dmitry Chernenkov <dmitryc@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      505f5dcb
  4. 17 Mar, 2016 4 commits
    • Joe Perches's avatar
      mm: coalesce split strings · 756a025f
      Joe Perches authored
      Kernel style prefers a single string over split strings when the string is
      'user-visible'.
      
      Miscellanea:
      
       - Add a missing newline
       - Realign arguments
      Signed-off-by: default avatarJoe Perches <joe@perches.com>
      Acked-by: Tejun Heo <tj@kernel.org>	[percpu]
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      756a025f
    • Mel Gorman's avatar
      mm: thp: set THP defrag by default to madvise and add a stall-free defrag option · 444eb2a4
      Mel Gorman authored
      THP defrag is enabled by default to direct reclaim/compact but not wake
      kswapd in the event of a THP allocation failure.  The problem is that
      THP allocation requests potentially enter reclaim/compaction.  This
      potentially incurs a severe stall that is not guaranteed to be offset by
      reduced TLB misses.  While there has been considerable effort to reduce
      the impact of reclaim/compaction, it is still a high cost and workloads
      that should fit in memory fail to do so.  Specifically, a simple
      anon/file streaming workload will enter direct reclaim on NUMA at least
      even though the working set size is 80% of RAM.  It's been years and
      it's time to throw in the towel.
      
      First, this patch defines THP defrag as follows;
      
       madvise: A failed allocation will direct reclaim/compact if the application requests it
       never:   Neither reclaim/compact nor wake kswapd
       defer:   A failed allocation will wake kswapd/kcompactd
       always:  A failed allocation will direct reclaim/compact (historical behaviour)
                khugepaged defrag will enter direct/reclaim but not wake kswapd.
      
      Next it sets the default defrag option to be "madvise" to only enter
      direct reclaim/compaction for applications that specifically requested
      it.
      
      Lastly, it removes a check from the page allocator slowpath that is
      related to __GFP_THISNODE to allow "defer" to work.  The callers that
      really cares are slub/slab and they are updated accordingly.  The slab
      one may be surprising because it also corrects a comment as kswapd was
      never woken up by that path.
      
      This means that a THP fault will no longer stall for most applications
      by default and the ideal for most users that get THP if they are
      immediately available.  There are still options for users that prefer a
      stall at startup of a new application by either restoring historical
      behaviour with "always" or pick a half-way point with "defer" where
      kswapd does some of the work in the background and wakes kcompactd if
      necessary.  THP defrag for khugepaged remains enabled and will enter
      direct/reclaim but no wakeup kswapd or kcompactd.
      
      After this patch a THP allocation failure will quickly fallback and rely
      on khugepaged to recover the situation at some time in the future.  In
      some cases, this will reduce THP usage but the benefit of THP is hard to
      measure and not a universal win where as a stall to reclaim/compaction
      is definitely measurable and can be painful.
      
      The first test for this is using "usemem" to read a large file and write
      a large anonymous mapping (to avoid the zero page) multiple times.  The
      total size of the mappings is 80% of RAM and the benchmark simply
      measures how long it takes to complete.  It uses multiple threads to see
      if that is a factor.  On UMA, the performance is almost identical so is
      not reported but on NUMA, we see this
      
      usemem
                                         4.4.0                 4.4.0
                                kcompactd-v1r1         nodefrag-v1r3
      Amean    System-1       102.86 (  0.00%)       46.81 ( 54.50%)
      Amean    System-4        37.85 (  0.00%)       34.02 ( 10.12%)
      Amean    System-7        48.12 (  0.00%)       46.89 (  2.56%)
      Amean    System-12       51.98 (  0.00%)       56.96 ( -9.57%)
      Amean    System-21       80.16 (  0.00%)       79.05 (  1.39%)
      Amean    System-30      110.71 (  0.00%)      107.17 (  3.20%)
      Amean    System-48      127.98 (  0.00%)      124.83 (  2.46%)
      Amean    Elapsd-1       185.84 (  0.00%)      105.51 ( 43.23%)
      Amean    Elapsd-4        26.19 (  0.00%)       25.58 (  2.33%)
      Amean    Elapsd-7        21.65 (  0.00%)       21.62 (  0.16%)
      Amean    Elapsd-12       18.58 (  0.00%)       17.94 (  3.43%)
      Amean    Elapsd-21       17.53 (  0.00%)       16.60 (  5.33%)
      Amean    Elapsd-30       17.45 (  0.00%)       17.13 (  1.84%)
      Amean    Elapsd-48       15.40 (  0.00%)       15.27 (  0.82%)
      
      For a single thread, the benchmark completes 43.23% faster with this
      patch applied with smaller benefits as the thread increases.  Similar,
      notice the large reduction in most cases in system CPU usage.  The
      overall CPU time is
      
                     4.4.0       4.4.0
              kcompactd-v1r1 nodefrag-v1r3
      User        10357.65    10438.33
      System       3988.88     3543.94
      Elapsed      2203.01     1634.41
      
      Which is substantial. Now, the reclaim figures
      
                                       4.4.0       4.4.0
                                kcompactd-v1r1nodefrag-v1r3
      Minor Faults                 128458477   278352931
      Major Faults                   2174976         225
      Swap Ins                      16904701           0
      Swap Outs                     17359627           0
      Allocation stalls                43611           0
      DMA allocs                           0           0
      DMA32 allocs                  19832646    19448017
      Normal allocs                614488453   580941839
      Movable allocs                       0           0
      Direct pages scanned          24163800           0
      Kswapd pages scanned                 0           0
      Kswapd pages reclaimed               0           0
      Direct pages reclaimed        20691346           0
      Compaction stalls                42263           0
      Compaction success                 938           0
      Compaction failures              41325           0
      
      This patch eliminates almost all swapping and direct reclaim activity.
      There is still overhead but it's from NUMA balancing which does not
      identify that it's pointless trying to do anything with this workload.
      
      I also tried the thpscale benchmark which forces a corner case where
      compaction can be used heavily and measures the latency of whether base
      or huge pages were used
      
      thpscale Fault Latencies
                                             4.4.0                 4.4.0
                                    kcompactd-v1r1         nodefrag-v1r3
      Amean    fault-base-1      5288.84 (  0.00%)     2817.12 ( 46.73%)
      Amean    fault-base-3      6365.53 (  0.00%)     3499.11 ( 45.03%)
      Amean    fault-base-5      6526.19 (  0.00%)     4363.06 ( 33.15%)
      Amean    fault-base-7      7142.25 (  0.00%)     4858.08 ( 31.98%)
      Amean    fault-base-12    13827.64 (  0.00%)    10292.11 ( 25.57%)
      Amean    fault-base-18    18235.07 (  0.00%)    13788.84 ( 24.38%)
      Amean    fault-base-24    21597.80 (  0.00%)    24388.03 (-12.92%)
      Amean    fault-base-30    26754.15 (  0.00%)    19700.55 ( 26.36%)
      Amean    fault-base-32    26784.94 (  0.00%)    19513.57 ( 27.15%)
      Amean    fault-huge-1      4223.96 (  0.00%)     2178.57 ( 48.42%)
      Amean    fault-huge-3      2194.77 (  0.00%)     2149.74 (  2.05%)
      Amean    fault-huge-5      2569.60 (  0.00%)     2346.95 (  8.66%)
      Amean    fault-huge-7      3612.69 (  0.00%)     2997.70 ( 17.02%)
      Amean    fault-huge-12     3301.75 (  0.00%)     6727.02 (-103.74%)
      Amean    fault-huge-18     6696.47 (  0.00%)     6685.72 (  0.16%)
      Amean    fault-huge-24     8000.72 (  0.00%)     9311.43 (-16.38%)
      Amean    fault-huge-30    13305.55 (  0.00%)     9750.45 ( 26.72%)
      Amean    fault-huge-32     9981.71 (  0.00%)    10316.06 ( -3.35%)
      
      The average time to fault pages is substantially reduced in the majority
      of caseds but with the obvious caveat that fewer THPs are actually used
      in this adverse workload
      
                                         4.4.0                 4.4.0
                                kcompactd-v1r1         nodefrag-v1r3
      Percentage huge-1         0.71 (  0.00%)       14.04 (1865.22%)
      Percentage huge-3        10.77 (  0.00%)       33.05 (206.85%)
      Percentage huge-5        60.39 (  0.00%)       38.51 (-36.23%)
      Percentage huge-7        45.97 (  0.00%)       34.57 (-24.79%)
      Percentage huge-12       68.12 (  0.00%)       40.07 (-41.17%)
      Percentage huge-18       64.93 (  0.00%)       47.82 (-26.35%)
      Percentage huge-24       62.69 (  0.00%)       44.23 (-29.44%)
      Percentage huge-30       43.49 (  0.00%)       55.38 ( 27.34%)
      Percentage huge-32       50.72 (  0.00%)       51.90 (  2.35%)
      
                                       4.4.0       4.4.0
                                kcompactd-v1r1nodefrag-v1r3
      Minor Faults                  37429143    47564000
      Major Faults                      1916        1558
      Swap Ins                          1466        1079
      Swap Outs                      2936863      149626
      Allocation stalls                62510           3
      DMA allocs                           0           0
      DMA32 allocs                   6566458     6401314
      Normal allocs                216361697   216538171
      Movable allocs                       0           0
      Direct pages scanned          25977580       17998
      Kswapd pages scanned                 0     3638931
      Kswapd pages reclaimed               0      207236
      Direct pages reclaimed         8833714          88
      Compaction stalls               103349           5
      Compaction success                 270           4
      Compaction failures             103079           1
      
      Note again that while this does swap as it's an aggressive workload, the
      direct relcim activity and allocation stalls is substantially reduced.
      There is some kswapd activity but ftrace showed that the kswapd activity
      was due to normal wakeups from 4K pages being allocated.
      Compaction-related stalls and activity are almost eliminated.
      
      I also tried the stutter benchmark.  For this, I do not have figures for
      NUMA but it's something that does impact UMA so I'll report what is
      available
      
      stutter
                                       4.4.0                 4.4.0
                              kcompactd-v1r1         nodefrag-v1r3
      Min         mmap      7.3571 (  0.00%)      7.3438 (  0.18%)
      1st-qrtle   mmap      7.5278 (  0.00%)     17.9200 (-138.05%)
      2nd-qrtle   mmap      7.6818 (  0.00%)     21.6055 (-181.25%)
      3rd-qrtle   mmap     11.0889 (  0.00%)     21.8881 (-97.39%)
      Max-90%     mmap     27.8978 (  0.00%)     22.1632 ( 20.56%)
      Max-93%     mmap     28.3202 (  0.00%)     22.3044 ( 21.24%)
      Max-95%     mmap     28.5600 (  0.00%)     22.4580 ( 21.37%)
      Max-99%     mmap     29.6032 (  0.00%)     25.5216 ( 13.79%)
      Max         mmap   4109.7289 (  0.00%)   4813.9832 (-17.14%)
      Mean        mmap     12.4474 (  0.00%)     19.3027 (-55.07%)
      
      This benchmark is trying to fault an anonymous mapping while there is a
      heavy IO load -- a scenario that desktop users used to complain about
      frequently.  This shows a mix because the ideal case of mapping with THP
      is not hit as often.  However, note that 99% of the mappings complete
      13.79% faster.  The CPU usage here is particularly interesting
      
                     4.4.0       4.4.0
              kcompactd-v1r1nodefrag-v1r3
      User           67.50        0.99
      System       1327.88       91.30
      Elapsed      2079.00     2128.98
      
      And once again we look at the reclaim figures
      
                                       4.4.0       4.4.0
                                kcompactd-v1r1nodefrag-v1r3
      Minor Faults                 335241922  1314582827
      Major Faults                       715         819
      Swap Ins                             0           0
      Swap Outs                            0           0
      Allocation stalls               532723           0
      DMA allocs                           0           0
      DMA32 allocs                1822364341  1177950222
      Normal allocs               1815640808  1517844854
      Movable allocs                       0           0
      Direct pages scanned          21892772           0
      Kswapd pages scanned          20015890    41879484
      Kswapd pages reclaimed        19961986    41822072
      Direct pages reclaimed        21892741           0
      Compaction stalls              1065755           0
      Compaction success                 514           0
      Compaction failures            1065241           0
      
      Allocation stalls and all direct reclaim activity is eliminated as well
      as compaction-related stalls.
      
      THP gives impressive gains in some cases but only if they are quickly
      available.  We're not going to reach the point where they are completely
      free so lets take the costs out of the fast paths finally and defer the
      cost to kswapd, kcompactd and khugepaged where it belongs.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarRik van Riel <riel@redhat.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      444eb2a4
    • Joonsoo Kim's avatar
      mm/slub: query dynamic DEBUG_PAGEALLOC setting · 922d566c
      Joonsoo Kim authored
      We can disable debug_pagealloc processing even if the code is compiled
      with CONFIG_DEBUG_PAGEALLOC.  This patch changes the code to query
      whether it is enabled or not in runtime.
      
      [akpm@linux-foundation.org: clean up code, per Christian]
      Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
      Reviewed-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: Takashi Iwai <tiwai@suse.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      922d566c
    • Vladimir Davydov's avatar
      mm: memcontrol: report slab usage in cgroup2 memory.stat · 27ee57c9
      Vladimir Davydov authored
      Show how much memory is used for storing reclaimable and unreclaimable
      in-kernel data structures allocated from slab caches.
      Signed-off-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      27ee57c9
  5. 15 Mar, 2016 9 commits
    • Vlastimil Babka's avatar
      mm, sl[au]b: print gfp_flags as strings in slab_out_of_memory() · 5b3810e5
      Vlastimil Babka authored
      We can now print gfp_flags more human-readable.  Make use of this in
      slab_out_of_memory() for SLUB and SLAB.  Also convert the SLAB variant
      it to pr_warn() along the way.
      Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5b3810e5
    • Joonsoo Kim's avatar
      mm/slub: support left redzone · d86bd1be
      Joonsoo Kim authored
      SLUB already has a redzone debugging feature.  But it is only positioned
      at the end of object (aka right redzone) so it cannot catch left oob.
      Although current object's right redzone acts as left redzone of next
      object, first object in a slab cannot take advantage of this effect.
      This patch explicitly adds a left red zone to each object to detect left
      oob more precisely.
      
      Background:
      
      Someone complained to me that left OOB doesn't catch even if KASAN is
      enabled which does page allocation debugging.  That page is out of our
      control so it would be allocated when left OOB happens and, in this
      case, we can't find OOB.  Moreover, SLUB debugging feature can be
      enabled without page allocator debugging and, in this case, we will miss
      that OOB.
      
      Before trying to implement, I expected that changes would be too
      complex, but, it doesn't look that complex to me now.  Almost changes
      are applied to debug specific functions so I feel okay.
      Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d86bd1be
    • Laura Abbott's avatar
      slub: relax CMPXCHG consistency restrictions · 149daaf3
      Laura Abbott authored
      When debug options are enabled, cmpxchg on the page is disabled.  This
      is because the page must be locked to ensure there are no false
      positives when performing consistency checks.  Some debug options such
      as poisoning and red zoning only act on the object itself.  There is no
      need to protect other CPUs from modification on only the object.  Allow
      cmpxchg to happen with poisoning and red zoning are set on a slab.
      
      Credit to Mathias Krause for the original work which inspired this
      series
      Signed-off-by: default avatarLaura Abbott <labbott@fedoraproject.org>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Mathias Krause <minipli@googlemail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      149daaf3
    • Laura Abbott's avatar
      slub: convert SLAB_DEBUG_FREE to SLAB_CONSISTENCY_CHECKS · becfda68
      Laura Abbott authored
      SLAB_DEBUG_FREE allows expensive consistency checks at free to be turned
      on or off.  Expand its use to be able to turn off all consistency
      checks.  This gives a nice speed up if you only want features such as
      poisoning or tracing.
      
      Credit to Mathias Krause for the original work which inspired this
      series
      Signed-off-by: default avatarLaura Abbott <labbott@fedoraproject.org>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Mathias Krause <minipli@googlemail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      becfda68
    • Laura Abbott's avatar
      slub: fix/clean free_debug_processing return paths · 804aa132
      Laura Abbott authored
      Since commit 19c7ff9e ("slub: Take node lock during object free
      checks") check_object has been incorrectly returning success as it
      follows the out label which just returns the node.
      
      Thanks to refactoring, the out and fail paths are now basically the
      same.  Combine the two into one and just use a single label.
      
      Credit to Mathias Krause for the original work which inspired this
      series
      Signed-off-by: default avatarLaura Abbott <labbott@fedoraproject.org>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Mathias Krause <minipli@googlemail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      804aa132
    • Laura Abbott's avatar
      slub: drop lock at the end of free_debug_processing · 282acb43
      Laura Abbott authored
      This series takes the suggestion of Christoph Lameter and only focuses
      on optimizing the slow path where the debug processing runs.  The two
      main optimizations in this series are letting the consistency checks be
      skipped and relaxing the cmpxchg restrictions when we are not doing
      consistency checks.  With hackbench -g 20 -l 1000 averaged over 100
      runs:
      
      Before slub_debug=P
        mean 15.607
        variance .086
        stdev .294
      
      After slub_debug=P
        mean 10.836
        variance .155
        stdev .394
      
      This still isn't as fast as what is in grsecurity unfortunately so there's
      still work to be done.  Profiling ___slab_alloc shows that 25-50% of time
      is spent in deactivate_slab.  I haven't looked too closely to see if this
      is something that can be optimized.  My plan for now is to focus on
      getting all of this merged (if appropriate) before digging in to another
      task.
      
      This patch (of 4):
      
      Currently, free_debug_processing has a comment "Keep node_lock to preserve
      integrity until the object is actually freed".  In actuallity, the lock is
      dropped immediately in __slab_free.  Rather than wait until __slab_free
      and potentially throw off the unlikely marking, just drop the lock in
      __slab_free.  This also lets free_debug_processing take its own copy of
      the spinlock flags rather than trying to share the ones from __slab_free.
      Since there is no use for the node afterwards, change the return type of
      free_debug_processing to return an int like alloc_debug_processing.
      
      Credit to Mathias Krause for the original work which inspired this series
      
      [akpm@linux-foundation.org: fix build]
      Signed-off-by: default avatarLaura Abbott <labbott@fedoraproject.org>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Mathias Krause <minipli@googlemail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      282acb43
    • Jesper Dangaard Brouer's avatar
      mm: new API kfree_bulk() for SLAB+SLUB allocators · ca257195
      Jesper Dangaard Brouer authored
      This patch introduce a new API call kfree_bulk() for bulk freeing memory
      objects not bound to a single kmem_cache.
      
      Christoph pointed out that it is possible to implement freeing of
      objects, without knowing the kmem_cache pointer as that information is
      available from the object's page->slab_cache.  Proposing to remove the
      kmem_cache argument from the bulk free API.
      
      Jesper demonstrated that these extra steps per object comes at a
      performance cost.  It is only in the case CONFIG_MEMCG_KMEM is compiled
      in and activated runtime that these steps are done anyhow.  The extra
      cost is most visible for SLAB allocator, because the SLUB allocator does
      the page lookup (virt_to_head_page()) anyhow.
      
      Thus, the conclusion was to keep the kmem_cache free bulk API with a
      kmem_cache pointer, but we can still implement a kfree_bulk() API fairly
      easily.  Simply by handling if kmem_cache_free_bulk() gets called with a
      kmem_cache NULL pointer.
      
      This does increase the code size a bit, but implementing a separate
      kfree_bulk() call would likely increase code size even more.
      
      Below benchmarks cost of alloc+free (obj size 256 bytes) on CPU i7-4790K
      @ 4.00GHz, no PREEMPT and CONFIG_MEMCG_KMEM=y.
      
      Code size increase for SLAB:
      
       add/remove: 0/0 grow/shrink: 1/0 up/down: 74/0 (74)
       function                                     old     new   delta
       kmem_cache_free_bulk                         660     734     +74
      
      SLAB fastpath: 87 cycles(tsc) 21.814
        sz - fallback             - kmem_cache_free_bulk - kfree_bulk
         1 - 103 cycles 25.878 ns -  41 cycles 10.498 ns - 81 cycles 20.312 ns
         2 -  94 cycles 23.673 ns -  26 cycles  6.682 ns - 42 cycles 10.649 ns
         3 -  92 cycles 23.181 ns -  21 cycles  5.325 ns - 39 cycles 9.950 ns
         4 -  90 cycles 22.727 ns -  18 cycles  4.673 ns - 26 cycles 6.693 ns
         8 -  89 cycles 22.270 ns -  14 cycles  3.664 ns - 23 cycles 5.835 ns
        16 -  88 cycles 22.038 ns -  14 cycles  3.503 ns - 22 cycles 5.543 ns
        30 -  89 cycles 22.284 ns -  13 cycles  3.310 ns - 20 cycles 5.197 ns
        32 -  88 cycles 22.249 ns -  13 cycles  3.420 ns - 20 cycles 5.166 ns
        34 -  88 cycles 22.224 ns -  14 cycles  3.643 ns - 20 cycles 5.170 ns
        48 -  88 cycles 22.088 ns -  14 cycles  3.507 ns - 20 cycles 5.203 ns
        64 -  88 cycles 22.063 ns -  13 cycles  3.428 ns - 20 cycles 5.152 ns
       128 -  89 cycles 22.483 ns -  15 cycles  3.891 ns - 23 cycles 5.885 ns
       158 -  89 cycles 22.381 ns -  15 cycles  3.779 ns - 22 cycles 5.548 ns
       250 -  91 cycles 22.798 ns -  16 cycles  4.152 ns - 23 cycles 5.967 ns
      
      SLAB when enabling MEMCG_KMEM runtime:
       - kmemcg fastpath: 130 cycles(tsc) 32.684 ns (step:0)
       1 - 148 cycles 37.220 ns -  66 cycles 16.622 ns - 66 cycles 16.583 ns
       2 - 141 cycles 35.510 ns -  51 cycles 12.820 ns - 58 cycles 14.625 ns
       3 - 140 cycles 35.017 ns -  37 cycles 9.326 ns - 33 cycles 8.474 ns
       4 - 137 cycles 34.507 ns -  31 cycles 7.888 ns - 33 cycles 8.300 ns
       8 - 140 cycles 35.069 ns -  25 cycles 6.461 ns - 25 cycles 6.436 ns
       16 - 138 cycles 34.542 ns -  23 cycles 5.945 ns - 22 cycles 5.670 ns
       30 - 136 cycles 34.227 ns -  22 cycles 5.502 ns - 22 cycles 5.587 ns
       32 - 136 cycles 34.253 ns -  21 cycles 5.475 ns - 21 cycles 5.324 ns
       34 - 136 cycles 34.254 ns -  21 cycles 5.448 ns - 20 cycles 5.194 ns
       48 - 136 cycles 34.075 ns -  21 cycles 5.458 ns - 21 cycles 5.367 ns
       64 - 135 cycles 33.994 ns -  21 cycles 5.350 ns - 21 cycles 5.259 ns
       128 - 137 cycles 34.446 ns -  23 cycles 5.816 ns - 22 cycles 5.688 ns
       158 - 137 cycles 34.379 ns -  22 cycles 5.727 ns - 22 cycles 5.602 ns
       250 - 138 cycles 34.755 ns -  24 cycles 6.093 ns - 23 cycles 5.986 ns
      
      Code size increase for SLUB:
       function                                     old     new   delta
       kmem_cache_free_bulk                         717     799     +82
      
      SLUB benchmark:
       SLUB fastpath: 46 cycles(tsc) 11.691 ns (step:0)
        sz - fallback             - kmem_cache_free_bulk - kfree_bulk
         1 -  61 cycles 15.486 ns -  53 cycles 13.364 ns - 57 cycles 14.464 ns
         2 -  54 cycles 13.703 ns -  32 cycles  8.110 ns - 33 cycles 8.482 ns
         3 -  53 cycles 13.272 ns -  25 cycles  6.362 ns - 27 cycles 6.947 ns
         4 -  51 cycles 12.994 ns -  24 cycles  6.087 ns - 24 cycles 6.078 ns
         8 -  50 cycles 12.576 ns -  21 cycles  5.354 ns - 22 cycles 5.513 ns
        16 -  49 cycles 12.368 ns -  20 cycles  5.054 ns - 20 cycles 5.042 ns
        30 -  49 cycles 12.273 ns -  18 cycles  4.748 ns - 19 cycles 4.758 ns
        32 -  49 cycles 12.401 ns -  19 cycles  4.821 ns - 19 cycles 4.810 ns
        34 -  98 cycles 24.519 ns -  24 cycles  6.154 ns - 24 cycles 6.157 ns
        48 -  83 cycles 20.833 ns -  21 cycles  5.446 ns - 21 cycles 5.429 ns
        64 -  75 cycles 18.891 ns -  20 cycles  5.247 ns - 20 cycles 5.238 ns
       128 -  93 cycles 23.271 ns -  27 cycles  6.856 ns - 27 cycles 6.823 ns
       158 - 102 cycles 25.581 ns -  30 cycles  7.714 ns - 30 cycles 7.695 ns
       250 - 107 cycles 26.917 ns -  38 cycles  9.514 ns - 38 cycles 9.506 ns
      
      SLUB when enabling MEMCG_KMEM runtime:
       - kmemcg fastpath: 71 cycles(tsc) 17.897 ns (step:0)
       1 - 85 cycles 21.484 ns -  78 cycles 19.569 ns - 75 cycles 18.938 ns
       2 - 81 cycles 20.363 ns -  45 cycles 11.258 ns - 44 cycles 11.076 ns
       3 - 78 cycles 19.709 ns -  33 cycles 8.354 ns - 32 cycles 8.044 ns
       4 - 77 cycles 19.430 ns -  28 cycles 7.216 ns - 28 cycles 7.003 ns
       8 - 101 cycles 25.288 ns -  23 cycles 5.849 ns - 23 cycles 5.787 ns
       16 - 76 cycles 19.148 ns -  20 cycles 5.162 ns - 20 cycles 5.081 ns
       30 - 76 cycles 19.067 ns -  19 cycles 4.868 ns - 19 cycles 4.821 ns
       32 - 76 cycles 19.052 ns -  19 cycles 4.857 ns - 19 cycles 4.815 ns
       34 - 121 cycles 30.291 ns -  25 cycles 6.333 ns - 25 cycles 6.268 ns
       48 - 108 cycles 27.111 ns -  21 cycles 5.498 ns - 21 cycles 5.458 ns
       64 - 100 cycles 25.164 ns -  20 cycles 5.242 ns - 20 cycles 5.229 ns
       128 - 155 cycles 38.976 ns -  27 cycles 6.886 ns - 27 cycles 6.892 ns
       158 - 132 cycles 33.034 ns -  30 cycles 7.711 ns - 30 cycles 7.728 ns
       250 - 130 cycles 32.612 ns -  38 cycles 9.560 ns - 38 cycles 9.549 ns
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ca257195
    • Jesper Dangaard Brouer's avatar
      mm/slab: move SLUB alloc hooks to common mm/slab.h · 11c7aec2
      Jesper Dangaard Brouer authored
      First step towards sharing alloc_hook's between SLUB and SLAB
      allocators.  Move the SLUB allocators *_alloc_hook to the common
      mm/slab.h for internal slab definitions.
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      11c7aec2
    • Jesper Dangaard Brouer's avatar
      slub: clean up code for kmem cgroup support to kmem_cache_free_bulk · 376bf125
      Jesper Dangaard Brouer authored
      This change is primarily an attempt to make it easier to realize the
      optimizations the compiler performs in-case CONFIG_MEMCG_KMEM is not
      enabled.
      
      Performance wise, even when CONFIG_MEMCG_KMEM is compiled in, the
      overhead is zero.  This is because, as long as no process have enabled
      kmem cgroups accounting, the assignment is replaced by asm-NOP
      operations.  This is possible because memcg_kmem_enabled() uses a
      static_key_false() construct.
      
      It also helps readability as it avoid accessing the p[] array like:
      p[size - 1] which "expose" that the array is processed backwards inside
      helper function build_detached_freelist().
      
      Lastly this also makes the code more robust, in error case like passing
      NULL pointers in the array.  Which were previously handled before commit
      03374518 ("slub: add missing kmem cgroup support to
      kmem_cache_free_bulk").
      
      Fixes: 03374518 ("slub: add missing kmem cgroup support to kmem_cache_free_bulk")
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      376bf125
  6. 18 Feb, 2016 1 commit
    • Dmitry Safonov's avatar
      mm: slab: free kmem_cache_node after destroy sysfs file · 52b4b950
      Dmitry Safonov authored
      When slub_debug alloc_calls_show is enabled we will try to track
      location and user of slab object on each online node, kmem_cache_node
      structure and cpu_cache/cpu_slub shouldn't be freed till there is the
      last reference to sysfs file.
      
      This fixes the following panic:
      
         BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
         IP:  list_locations+0x169/0x4e0
         PGD 257304067 PUD 438456067 PMD 0
         Oops: 0000 [#1] SMP
         CPU: 3 PID: 973074 Comm: cat ve: 0 Not tainted 3.10.0-229.7.2.ovz.9.30-00007-japdoll-dirty #2 9.30
         Hardware name: DEPO Computers To Be Filled By O.E.M./H67DE3, BIOS L1.60c 07/14/2011
         task: ffff88042a5dc5b0 ti: ffff88037f8d8000 task.ti: ffff88037f8d8000
         RIP: list_locations+0x169/0x4e0
         Call Trace:
           alloc_calls_show+0x1d/0x30
           slab_attr_show+0x1b/0x30
           sysfs_read_file+0x9a/0x1a0
           vfs_read+0x9c/0x170
           SyS_read+0x58/0xb0
           system_call_fastpath+0x16/0x1b
         Code: 5e 07 12 00 b9 00 04 00 00 3d 00 04 00 00 0f 4f c1 3d 00 04 00 00 89 45 b0 0f 84 c3 00 00 00 48 63 45 b0 49 8b 9c c4 f8 00 00 00 <48> 8b 43 20 48 85 c0 74 b6 48 89 df e8 46 37 44 00 48 8b 53 10
         CR2: 0000000000000020
      
      Separated __kmem_cache_release from __kmem_cache_shutdown which now
      called on slab_kmem_cache_release (after the last reference to sysfs
      file object has dropped).
      
      Reintroduced locking in free_partial as sysfs file might access cache's
      partial list after shutdowning - partial revert of the commit
      69cb8e6b ("slub: free slabs without holding locks").  Zap
      __remove_partial and use remove_partial (w/o underscores) as
      free_partial now takes list_lock which s partial revert for commit
      1e4dd946 ("slub: do not assert not having lock in removing freed
      partial")
      Signed-off-by: default avatarDmitry Safonov <dsafonov@virtuozzo.com>
      Suggested-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Acked-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      52b4b950
  7. 20 Jan, 2016 1 commit
  8. 15 Jan, 2016 1 commit
    • Kirill A. Shutemov's avatar
      page-flags: define PG_locked behavior on compound pages · 48c935ad
      Kirill A. Shutemov authored
      lock_page() must operate on the whole compound page.  It doesn't make
      much sense to lock part of compound page.  Change code to use head
      page's PG_locked, if tail page is passed.
      
      This patch also gets rid of custom helper functions --
      __set_page_locked() and __clear_page_locked().  They are replaced with
      helpers generated by __SETPAGEFLAG/__CLEARPAGEFLAG.  Tail pages to these
      helper would trigger VM_BUG_ON().
      
      SLUB uses PG_locked as a bit spin locked.  IIUC, tail pages should never
      appear there.  VM_BUG_ON() is added to make sure that this assumption is
      correct.
      
      [akpm@linux-foundation.org: fix fs/cifs/file.c]
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Steve Capper <steve.capper@linaro.org>
      Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Jerome Marchand <jmarchan@redhat.com>
      Cc: Jérôme Glisse <jglisse@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      48c935ad
  9. 14 Jan, 2016 1 commit
    • Vladimir Davydov's avatar
      slab: add SLAB_ACCOUNT flag · 230e9fc2
      Vladimir Davydov authored
      Currently, if we want to account all objects of a particular kmem cache,
      we have to pass __GFP_ACCOUNT to each kmem_cache_alloc call, which is
      inconvenient.  This patch introduces SLAB_ACCOUNT flag which if passed
      to kmem_cache_create will force accounting for every allocation from
      this cache even if __GFP_ACCOUNT is not passed.
      
      This patch does not make any of the existing caches use this flag - it
      will be done later in the series.
      
      Note, a cache with SLAB_ACCOUNT cannot be merged with a cache w/o
      SLAB_ACCOUNT, because merged caches share the same kmem_cache struct and
      hence cannot have different sets of SLAB_* flags.  Thus using this flag
      will probably reduce the number of merged slabs even if kmem accounting
      is not used (only compiled in).
      Signed-off-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Suggested-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      230e9fc2
  10. 22 Nov, 2015 5 commits
    • Jesper Dangaard Brouer's avatar
      slab/slub: adjust kmem_cache_alloc_bulk API · 865762a8
      Jesper Dangaard Brouer authored
      Adjust kmem_cache_alloc_bulk API before we have any real users.
      
      Adjust API to return type 'int' instead of previously type 'bool'.  This
      is done to allow future extension of the bulk alloc API.
      
      A future extension could be to allow SLUB to stop at a page boundary, when
      specified by a flag, and then return the number of objects.
      
      The advantage of this approach, would make it easier to make bulk alloc
      run without local IRQs disabled.  With an approach of cmpxchg "stealing"
      the entire c->freelist or page->freelist.  To avoid overshooting we would
      stop processing at a slab-page boundary.  Else we always end up returning
      some objects at the cost of another cmpxchg.
      
      To keep compatible with future users of this API linking against an older
      kernel when using the new flag, we need to return the number of allocated
      objects with this API change.
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      865762a8
    • Jesper Dangaard Brouer's avatar
      slub: add missing kmem cgroup support to kmem_cache_free_bulk · 03374518
      Jesper Dangaard Brouer authored
      Initial implementation missed support for kmem cgroup support in
      kmem_cache_free_bulk() call, add this.
      
      If CONFIG_MEMCG_KMEM is not enabled, the compiler should be smart enough
      to not add any asm code.
      
      Incoming bulk free objects can belong to different kmem cgroups, and
      object free call can happen at a later point outside memcg context.  Thus,
      we need to keep the orig kmem_cache, to correctly verify if a memcg object
      match against its "root_cache" (s->memcg_params.root_cache).
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Reviewed-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      03374518
    • Jesper Dangaard Brouer's avatar
      slub: fix kmem cgroup bug in kmem_cache_alloc_bulk · 03ec0ed5
      Jesper Dangaard Brouer authored
      The call slab_pre_alloc_hook() interacts with kmemgc and is not allowed to
      be called several times inside the bulk alloc for loop, due to the call to
      memcg_kmem_get_cache().
      
      This would result in hitting the VM_BUG_ON in __memcg_kmem_get_cache.
      
      As suggested by Vladimir Davydov, change slab_post_alloc_hook() to be able
      to handle an array of objects.
      
      A subtle detail is, loop iterator "i" in slab_post_alloc_hook() must have
      same type (size_t) as size argument.  This helps the compiler to easier
      realize that it can remove the loop, when all debug statements inside loop
      evaluates to nothing.  Note, this is only an issue because the kernel is
      compiled with GCC option: -fno-strict-overflow
      
      In slab_alloc_node() the compiler inlines and optimizes the invocation of
      slab_post_alloc_hook(s, flags, 1, &object) by removing the loop and access
      object directly.
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Reported-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Suggested-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Reviewed-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      03ec0ed5
    • Jesper Dangaard Brouer's avatar
      slub: optimize bulk slowpath free by detached freelist · d0ecd894
      Jesper Dangaard Brouer authored
      This change focus on improving the speed of object freeing in the
      "slowpath" of kmem_cache_free_bulk.
      
      The calls slab_free (fastpath) and __slab_free (slowpath) have been
      extended with support for bulk free, which amortize the overhead of
      the (locked) cmpxchg_double.
      
      To use the new bulking feature, we build what I call a detached
      freelist.  The detached freelist takes advantage of three properties:
      
       1) the free function call owns the object that is about to be freed,
          thus writing into this memory is synchronization-free.
      
       2) many freelist's can co-exist side-by-side in the same slab-page
          each with a separate head pointer.
      
       3) it is the visibility of the head pointer that needs synchronization.
      
      Given these properties, the brilliant part is that the detached
      freelist can be constructed without any need for synchronization.  The
      freelist is constructed directly in the page objects, without any
      synchronization needed.  The detached freelist is allocated on the
      stack of the function call kmem_cache_free_bulk.  Thus, the freelist
      head pointer is not visible to other CPUs.
      
      All objects in a SLUB freelist must belong to the same slab-page.
      Thus, constructing the detached freelist is about matching objects
      that belong to the same slab-page.  The bulk free array is scanned is
      a progressive manor with a limited look-ahead facility.
      
      Kmem debug support is handled in call of slab_free().
      
      Notice kmem_cache_free_bulk no longer need to disable IRQs. This
      only slowed down single free bulk with approx 3 cycles.
      
      Performance data:
       Benchmarked[1] obj size 256 bytes on CPU i7-4790K @ 4.00GHz
      
      SLUB fastpath single object quick reuse: 47 cycles(tsc) 11.931 ns
      
      To get stable and comparable numbers, the kernel have been booted with
      "slab_merge" (this also improve performance for larger bulk sizes).
      
      Performance data, compared against fallback bulking:
      
      bulk -  fallback bulk            - improvement with this patch
         1 -  62 cycles(tsc) 15.662 ns - 49 cycles(tsc) 12.407 ns- improved 21.0%
         2 -  55 cycles(tsc) 13.935 ns - 30 cycles(tsc) 7.506 ns - improved 45.5%
         3 -  53 cycles(tsc) 13.341 ns - 23 cycles(tsc) 5.865 ns - improved 56.6%
         4 -  52 cycles(tsc) 13.081 ns - 20 cycles(tsc) 5.048 ns - improved 61.5%
         8 -  50 cycles(tsc) 12.627 ns - 18 cycles(tsc) 4.659 ns - improved 64.0%
        16 -  49 cycles(tsc) 12.412 ns - 17 cycles(tsc) 4.495 ns - improved 65.3%
        30 -  49 cycles(tsc) 12.484 ns - 18 cycles(tsc) 4.533 ns - improved 63.3%
        32 -  50 cycles(tsc) 12.627 ns - 18 cycles(tsc) 4.707 ns - improved 64.0%
        34 -  96 cycles(tsc) 24.243 ns - 23 cycles(tsc) 5.976 ns - improved 76.0%
        48 -  83 cycles(tsc) 20.818 ns - 21 cycles(tsc) 5.329 ns - improved 74.7%
        64 -  74 cycles(tsc) 18.700 ns - 20 cycles(tsc) 5.127 ns - improved 73.0%
       128 -  90 cycles(tsc) 22.734 ns - 27 cycles(tsc) 6.833 ns - improved 70.0%
       158 -  99 cycles(tsc) 24.776 ns - 30 cycles(tsc) 7.583 ns - improved 69.7%
       250 - 104 cycles(tsc) 26.089 ns - 37 cycles(tsc) 9.280 ns - improved 64.4%
      
      Performance data, compared current in-kernel bulking:
      
      bulk - curr in-kernel  - improvement with this patch
         1 -  46 cycles(tsc) - 49 cycles(tsc) - improved (cycles:-3) -6.5%
         2 -  27 cycles(tsc) - 30 cycles(tsc) - improved (cycles:-3) -11.1%
         3 -  21 cycles(tsc) - 23 cycles(tsc) - improved (cycles:-2) -9.5%
         4 -  18 cycles(tsc) - 20 cycles(tsc) - improved (cycles:-2) -11.1%
         8 -  17 cycles(tsc) - 18 cycles(tsc) - improved (cycles:-1) -5.9%
        16 -  18 cycles(tsc) - 17 cycles(tsc) - improved (cycles: 1)  5.6%
        30 -  18 cycles(tsc) - 18 cycles(tsc) - improved (cycles: 0)  0.0%
        32 -  18 cycles(tsc) - 18 cycles(tsc) - improved (cycles: 0)  0.0%
        34 -  78 cycles(tsc) - 23 cycles(tsc) - improved (cycles:55) 70.5%
        48 -  60 cycles(tsc) - 21 cycles(tsc) - improved (cycles:39) 65.0%
        64 -  49 cycles(tsc) - 20 cycles(tsc) - improved (cycles:29) 59.2%
       128 -  69 cycles(tsc) - 27 cycles(tsc) - improved (cycles:42) 60.9%
       158 -  79 cycles(tsc) - 30 cycles(tsc) - improved (cycles:49) 62.0%
       250 -  86 cycles(tsc) - 37 cycles(tsc) - improved (cycles:49) 57.0%
      
      Performance with normal SLUB merging is significantly slower for
      larger bulking.  This is believed to (primarily) be an effect of not
      having to share the per-CPU data-structures, as tuning per-CPU size
      can achieve similar performance.
      
      bulk - slab_nomerge   -  normal SLUB merge
         1 -  49 cycles(tsc) - 49 cycles(tsc) - merge slower with cycles:0
         2 -  30 cycles(tsc) - 30 cycles(tsc) - merge slower with cycles:0
         3 -  23 cycles(tsc) - 23 cycles(tsc) - merge slower with cycles:0
         4 -  20 cycles(tsc) - 20 cycles(tsc) - merge slower with cycles:0
         8 -  18 cycles(tsc) - 18 cycles(tsc) - merge slower with cycles:0
        16 -  17 cycles(tsc) - 17 cycles(tsc) - merge slower with cycles:0
        30 -  18 cycles(tsc) - 23 cycles(tsc) - merge slower with cycles:5
        32 -  18 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:4
        34 -  23 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:-1
        48 -  21 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:1
        64 -  20 cycles(tsc) - 48 cycles(tsc) - merge slower with cycles:28
       128 -  27 cycles(tsc) - 57 cycles(tsc) - merge slower with cycles:30
       158 -  30 cycles(tsc) - 59 cycles(tsc) - merge slower with cycles:29
       250 -  37 cycles(tsc) - 56 cycles(tsc) - merge slower with cycles:19
      
      Joint work with Alexander Duyck.
      
      [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/slab_bulk_test01.c
      
      [akpm@linux-foundation.org: BUG_ON -> WARN_ON;return]
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@redhat.com>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d0ecd894
    • Jesper Dangaard Brouer's avatar
      slub: support for bulk free with SLUB freelists · 81084651
      Jesper Dangaard Brouer authored
      Make it possible to free a freelist with several objects by adjusting API
      of slab_free() and __slab_free() to have head, tail and an objects counter
      (cnt).
      
      Tail being NULL indicate single object free of head object.  This allow
      compiler inline constant propagation in slab_free() and
      slab_free_freelist_hook() to avoid adding any overhead in case of single
      object free.
      
      This allows a freelist with several objects (all within the same
      slab-page) to be free'ed using a single locked cmpxchg_double in
      __slab_free() and with an unlocked cmpxchg_double in slab_free().
      
      Object debugging on the free path is also extended to handle these
      freelists.  When CONFIG_SLUB_DEBUG is enabled it will also detect if
      objects don't belong to the same slab-page.
      
      These changes are needed for the next patch to bulk free the detached
      freelists it introduces and constructs.
      
      Micro benchmarking showed no performance reduction due to this change,
      when debugging is turned off (compiled with CONFIG_SLUB_DEBUG).
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@redhat.com>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      81084651
  11. 20 Nov, 2015 3 commits
  12. 06 Nov, 2015 2 commits
    • Kirill A. Shutemov's avatar
      slab, slub: use page->rcu_head instead of page->lru plus cast · bc4f610d
      Kirill A. Shutemov authored
      We have properly typed page->rcu_head, no need to cast page->lru.
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Michal Hocko <mhocko@suse.com>
      Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      bc4f610d
    • Mel Gorman's avatar
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep... · d0164adc
      Mel Gorman authored
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd
      
      __GFP_WAIT has been used to identify atomic context in callers that hold
      spinlocks or are in interrupts.  They are expected to be high priority and
      have access one of two watermarks lower than "min" which can be referred
      to as the "atomic reserve".  __GFP_HIGH users get access to the first
      lower watermark and can be called the "high priority reserve".
      
      Over time, callers had a requirement to not block when fallback options
      were available.  Some have abused __GFP_WAIT leading to a situation where
      an optimisitic allocation with a fallback option can access atomic
      reserves.
      
      This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
      cannot sleep and have no alternative.  High priority users continue to use
      __GFP_HIGH.  __GFP_DIRECT_RECLAIM identifies callers that can sleep and
      are willing to enter direct reclaim.  __GFP_KSWAPD_RECLAIM to identify
      callers that want to wake kswapd for background reclaim.  __GFP_WAIT is
      redefined as a caller that is willing to enter direct reclaim and wake
      kswapd for background reclaim.
      
      This patch then converts a number of sites
      
      o __GFP_ATOMIC is used by callers that are high priority and have memory
        pools for those requests. GFP_ATOMIC uses this flag.
      
      o Callers that have a limited mempool to guarantee forward progress clear
        __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
        into this category where kswapd will still be woken but atomic reserves
        are not used as there is a one-entry mempool to guarantee progress.
      
      o Callers that are checking if they are non-blocking should use the
        helper gfpflags_allow_blocking() where possible. This is because
        checking for __GFP_WAIT as was done historically now can trigger false
        positives. Some exceptions like dm-crypt.c exist where the code intent
        is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
        flag manipulations.
      
      o Callers that built their own GFP flags instead of starting with GFP_KERNEL
        and friends now also need to specify __GFP_KSWAPD_RECLAIM.
      
      The first key hazard to watch out for is callers that removed __GFP_WAIT
      and was depending on access to atomic reserves for inconspicuous reasons.
      In some cases it may be appropriate for them to use __GFP_HIGH.
      
      The second key hazard is callers that assembled their own combination of
      GFP flags instead of starting with something like GFP_KERNEL.  They may
      now wish to specify __GFP_KSWAPD_RECLAIM.  It's almost certainly harmless
      if it's missed in most cases as other activity will wake kswapd.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d0164adc
  13. 05 Nov, 2015 5 commits
  14. 08 Sep, 2015 1 commit
    • Vlastimil Babka's avatar
      mm: rename alloc_pages_exact_node() to __alloc_pages_node() · 96db800f
      Vlastimil Babka authored
      alloc_pages_exact_node() was introduced in commit 6484eb3e ("page
      allocator: do not check NUMA node ID when the caller knows the node is
      valid") as an optimized variant of alloc_pages_node(), that doesn't
      fallback to current node for nid == NUMA_NO_NODE.  Unfortunately the
      name of the function can easily suggest that the allocation is
      restricted to the given node and fails otherwise.  In truth, the node is
      only preferred, unless __GFP_THISNODE is passed among the gfp flags.
      
      The misleading name has lead to mistakes in the past, see for example
      commits 5265047a ("mm, thp: really limit transparent hugepage
      allocation to local node") and b360edb4 ("mm, mempolicy:
      migrate_to_node should only migrate to node").
      
      Another issue with the name is that there's a family of
      alloc_pages_exact*() functions where 'exact' means exact size (instead
      of page order), which leads to more confusion.
      
      To prevent further mistakes, this patch effectively renames
      alloc_pages_exact_node() to __alloc_pages_node() to better convey that
      it's an optimized variant of alloc_pages_node() not intended for general
      usage.  Both functions get described in comments.
      
      It has been also considered to really provide a convenience function for
      allocations restricted to a node, but the major opinion seems to be that
      __GFP_THISNODE already provides that functionality and we shouldn't
      duplicate the API needlessly.  The number of users would be small
      anyway.
      
      Existing callers of alloc_pages_exact_node() are simply converted to
      call __alloc_pages_node(), with the exception of sba_alloc_coherent()
      which open-codes the check for NUMA_NO_NODE, so it is converted to use
      alloc_pages_node() instead.  This means it no longer performs some
      VM_BUG_ON checks, and since the current check for nid in
      alloc_pages_node() uses a 'nid < 0' comparison (which includes
      NUMA_NO_NODE), it may hide wrong values which would be previously
      exposed.
      
      Both differences will be rectified by the next patch.
      
      To sum up, this patch makes no functional changes, except temporarily
      hiding potentially buggy callers.  Restricting the checks in
      alloc_pages_node() is left for the next patch which can in turn expose
      more existing buggy callers.
      Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Acked-by: default avatarRobin Holt <robinmholt@gmail.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Gleb Natapov <gleb@kernel.org>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Cliff Whickman <cpw@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      96db800f
  15. 04 Sep, 2015 2 commits
    • Joonsoo Kim's avatar
      mm/slub: don't wait for high-order page allocation · 45eb00cd
      Joonsoo Kim authored
      Description is almost copied from commit fb05e7a8 ("net: don't wait
      for order-3 page allocation").
      
      I saw excessive direct memory reclaim/compaction triggered by slub.  This
      causes performance issues and add latency.  Slub uses high-order
      allocation to reduce internal fragmentation and management overhead.  But,
      direct memory reclaim/compaction has high overhead and the benefit of
      high-order allocation can't compensate the overhead of both work.
      
      This patch makes auxiliary high-order allocation atomic.  If there is no
      memory pressure and memory isn't fragmented, the alloction will still
      success, so we don't sacrifice high-order allocation's benefit here.  If
      the atomic allocation fails, direct memory reclaim/compaction will not be
      triggered, allocation fallback to low-order immediately, hence the direct
      memory reclaim/compaction overhead is avoided.  In the allocation failure
      case, kswapd is waken up and trying to make high-order freepages, so
      allocation could success next time.
      
      Following is the test to measure effect of this patch.
      
      System: QEMU, CPU 8, 512 MB
      Mem: 25% memory is allocated at random position to make fragmentation.
       Memory-hogger occupies 150 MB memory.
      Workload: hackbench -g 20 -l 1000
      
      Average result by 10 runs (Base va Patched)
      
      elapsed_time(s): 4.3468 vs 2.9838
      compact_stall: 461.7 vs 73.6
      pgmigrate_success: 28315.9 vs 7256.1
      Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Shaohua Li <shli@fb.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Eric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      45eb00cd
    • Konstantin Khlebnikov's avatar
      mm/slub: fix slab double-free in case of duplicate sysfs filename · 80da026a
      Konstantin Khlebnikov authored
      sysfs_slab_add() shouldn't call kobject_put at error path: this puts last
      reference of kmem-cache kobject and frees it.  Kmem cache will be freed
      second time at error path in kmem_cache_create().
      
      For example this happens when slub debug was enabled in runtime and
      somebody creates new kmem cache:
      
      # echo 1 | tee /sys/kernel/slab/*/sanity_checks
      # modprobe configfs
      
      "configfs_dir_cache" cannot be merged because existing slab have debug and
      cannot create new slab because unique name ":t-0000096" already taken.
      Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      80da026a