1. 11 9月, 2013 2 次提交
    • D
      shrinker: add node awareness · 0ce3d744
      Dave Chinner 提交于
      Pass the node of the current zone being reclaimed to shrink_slab(),
      allowing the shrinker control nodemask to be set appropriately for node
      aware shrinkers.
      Signed-off-by: NDave Chinner <dchinner@redhat.com>
      Signed-off-by: NGlauber Costa <glommer@openvz.org>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Cc: Adrian Hunter <adrian.hunter@intel.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
      Cc: Arve Hjønnevåg <arve@android.com>
      Cc: Carlos Maiolino <cmaiolino@redhat.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Chuck Lever <chuck.lever@oracle.com>
      Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Gleb Natapov <gleb@redhat.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: J. Bruce Fields <bfields@redhat.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Jerome Glisse <jglisse@redhat.com>
      Cc: John Stultz <john.stultz@linaro.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Kent Overstreet <koverstreet@google.com>
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Marcelo Tosatti <mtosatti@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Steven Whitehouse <swhiteho@redhat.com>
      Cc: Thomas Hellstrom <thellstrom@vmware.com>
      Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      0ce3d744
    • D
      mm: new shrinker API · 24f7c6b9
      Dave Chinner 提交于
      The current shrinker callout API uses an a single shrinker call for
      multiple functions.  To determine the function, a special magical value is
      passed in a parameter to change the behaviour.  This complicates the
      implementation and return value specification for the different
      behaviours.
      
      Separate the two different behaviours into separate operations, one to
      return a count of freeable objects in the cache, and another to scan a
      certain number of objects in the cache for freeing.  In defining these new
      operations, ensure the return values and resultant behaviours are clearly
      defined and documented.
      
      Modify shrink_slab() to use the new API and implement the callouts for all
      the existing shrinkers.
      Signed-off-by: NDave Chinner <dchinner@redhat.com>
      Signed-off-by: NGlauber Costa <glommer@parallels.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Cc: Adrian Hunter <adrian.hunter@intel.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
      Cc: Arve Hjønnevåg <arve@android.com>
      Cc: Carlos Maiolino <cmaiolino@redhat.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Chuck Lever <chuck.lever@oracle.com>
      Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Gleb Natapov <gleb@redhat.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: J. Bruce Fields <bfields@redhat.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Jerome Glisse <jglisse@redhat.com>
      Cc: John Stultz <john.stultz@linaro.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Kent Overstreet <koverstreet@google.com>
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Marcelo Tosatti <mtosatti@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Steven Whitehouse <swhiteho@redhat.com>
      Cc: Thomas Hellstrom <thellstrom@vmware.com>
      Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      24f7c6b9
  2. 10 7月, 2013 2 次提交
    • M
      mm: vmscan: do not scale writeback pages when deciding whether to set ZONE_WRITEBACK · 918fc718
      Mel Gorman 提交于
      After the patch "mm: vmscan: Flatten kswapd priority loop" was merged
      the scanning priority of kswapd changed.
      
      The priority now rises until it is scanning enough pages to meet the
      high watermark.  shrink_inactive_list sets ZONE_WRITEBACK if a number of
      pages were encountered under writeback but this value is scaled based on
      the priority.  As kswapd frequently scans with a higher priority now it
      is relatively easy to set ZONE_WRITEBACK.  This patch removes the
      scaling and treates writeback pages similar to how it treats unqueued
      dirty pages and congested pages.  The user-visible effect should be that
      kswapd will writeback fewer pages from reclaim context.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Dave Chinner <david@fromorbit.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      918fc718
    • M
      mm: vmscan: do not continue scanning if reclaim was aborted for compaction · 5a1c9cbc
      Mel Gorman 提交于
      Direct reclaim is not aborting to allow compaction to go ahead properly.
      do_try_to_free_pages is told to abort reclaim which is happily ignores
      and instead increases priority instead until it reaches 0 and starts
      shrinking file/anon equally.  This patch corrects the situation by
      aborting reclaim when requested instead of raising priority.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Dave Chinner <david@fromorbit.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5a1c9cbc
  3. 04 7月, 2013 16 次提交
    • M
      mm: remove lru parameter from __lru_cache_add and lru_cache_add_lru · c53954a0
      Mel Gorman 提交于
      Similar to __pagevec_lru_add, this patch removes the LRU parameter from
      __lru_cache_add and lru_cache_add_lru as the caller does not control the
      exact LRU the page gets added to.  lru_cache_add_lru gets renamed to
      lru_cache_add the name is silly without the lru parameter.  With the
      parameter removed, it is required that the caller indicate if they want
      the page added to the active or inactive list by setting or clearing
      PageActive respectively.
      
      [akpm@linux-foundation.org: Suggested the patch]
      [gang.chen@asianux.com: fix used-unintialized warning]
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Signed-off-by: NChen Gang <gang.chen@asianux.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Rik van Riel <riel@redhat.com>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Cc: Alexey Lyahkov <alexey.lyashkov@gmail.com>
      Cc: Andrew Perepechko <anserper@ya.ru>
      Cc: Robin Dong <sanbai@taobao.com>
      Cc: Theodore Tso <tytso@mit.edu>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Bernd Schubert <bernd.schubert@fastmail.fm>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c53954a0
    • M
      mm: vmscan: take page buffers dirty and locked state into account · b4597226
      Mel Gorman 提交于
      Page reclaim keeps track of dirty and under writeback pages and uses it
      to determine if wait_iff_congested() should stall or if kswapd should
      begin writing back pages.  This fails to account for buffer pages that
      can be under writeback but not PageWriteback which is the case for
      filesystems like ext3 ordered mode.  Furthermore, PageDirty buffer pages
      can have all the buffers clean and writepage does no IO so it should not
      be accounted as congested.
      
      This patch adds an address_space operation that filesystems may
      optionally use to check if a page is really dirty or really under
      writeback.  An implementation is provided for for buffer_heads is added
      and used for block operations and ext3 in ordered mode.  By default the
      page flags are obeyed.
      
      Credit goes to Jan Kara for identifying that the page flags alone are
      not sufficient for ext3 and sanity checking a number of ideas on how the
      problem could be addressed.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Cc: Zlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b4597226
    • M
      mm: vmscan: treat pages marked for immediate reclaim as zone congestion · d04e8acd
      Mel Gorman 提交于
      Currently a zone will only be marked congested if the underlying BDI is
      congested but if dirty pages are spread across zones it is possible that
      an individual zone is full of dirty pages without being congested.  The
      impact is that zone gets scanned very quickly potentially reclaiming
      really clean pages.  This patch treats pages marked for immediate
      reclaim as congested for the purposes of marking a zone ZONE_CONGESTED
      and stalling in wait_iff_congested.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Cc: Zlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d04e8acd
    • M
      mm: vmscan: move direct reclaim wait_iff_congested into shrink_list · 8e950282
      Mel Gorman 提交于
      shrink_inactive_list makes decisions on whether to stall based on the
      number of dirty pages encountered.  The wait_iff_congested() call in
      shrink_page_list does no such thing and it's arbitrary.
      
      This patch moves the decision on whether to set ZONE_CONGESTED and the
      wait_iff_congested call into shrink_page_list.  This keeps all the
      decisions on whether to stall or not in the one place.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Cc: Zlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8e950282
    • M
      mm: vmscan: set zone flags before blocking · f7ab8db7
      Mel Gorman 提交于
      In shrink_page_list a decision may be made to stall and flag a zone as
      ZONE_WRITEBACK so that if a large number of unqueued dirty pages are
      encountered later then the reclaimer will stall.  Set ZONE_WRITEBACK
      before potentially going to sleep so it is noticed sooner.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Cc: Zlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f7ab8db7
    • M
      mm: vmscan: stall page reclaim after a list of pages have been processed · b1a6f21e
      Mel Gorman 提交于
      Commit "mm: vmscan: Block kswapd if it is encountering pages under
      writeback" blocks page reclaim if it encounters pages under writeback
      marked for immediate reclaim.  It blocks while pages are still isolated
      from the LRU which is unnecessary.  This patch defers the blocking until
      after the isolated pages have been processed and tidies up some of the
      comments.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Cc: Zlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b1a6f21e
    • M
      mm: vmscan: stall page reclaim and writeback pages based on dirty/writepage pages encountered · e2be15f6
      Mel Gorman 提交于
      Further testing of the "Reduce system disruption due to kswapd"
      discovered a few problems.  First and foremost, it's possible for pages
      under writeback to be freed which will lead to badness.  Second, as
      pages were not being swapped the file LRU was being scanned faster and
      clean file pages were being reclaimed.  In some cases this results in
      increased read IO to re-read data from disk.  Third, more pages were
      being written from kswapd context which can adversly affect IO
      performance.  Lastly, it was observed that PageDirty pages are not
      necessarily dirty on all filesystems (buffers can be clean while
      PageDirty is set and ->writepage generates no IO) and not all
      filesystems set PageWriteback when the page is being written (e.g.
      ext3).  This disconnect confuses the reclaim stalling logic.  This
      follow-up series is aimed at these problems.
      
      The tests were based on three kernels
      
      vanilla:	kernel 3.9 as that is what the current mmotm uses as a baseline
      mmotm-20130522	is mmotm as of 22nd May with "Reduce system disruption due to
      		kswapd" applied on top as per what should be in Andrew's tree
      		right now
      lessdisrupt-v7r10 is this follow-up series on top of the mmotm kernel
      
      The first test used memcached+memcachetest while some background IO was
      in progress as implemented by the parallel IO tests implement in MM
      Tests.  memcachetest benchmarks how many operations/second memcached can
      service.  It starts with no background IO on a freshly created ext4
      filesystem and then re-runs the test with larger amounts of IO in the
      background to roughly simulate a large copy in progress.  The
      expectation is that the IO should have little or no impact on
      memcachetest which is running entirely in memory.
      
      parallelio
                                                   3.9.0                       3.9.0                       3.9.0
                                                 vanilla          mm1-mmotm-20130522       mm1-lessdisrupt-v7r10
      Ops memcachetest-0M             23117.00 (  0.00%)          22780.00 ( -1.46%)          22763.00 ( -1.53%)
      Ops memcachetest-715M           23774.00 (  0.00%)          23299.00 ( -2.00%)          22934.00 ( -3.53%)
      Ops memcachetest-2385M           4208.00 (  0.00%)          24154.00 (474.00%)          23765.00 (464.76%)
      Ops memcachetest-4055M           4104.00 (  0.00%)          25130.00 (512.33%)          24614.00 (499.76%)
      Ops io-duration-0M                  0.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops io-duration-715M               12.00 (  0.00%)              7.00 ( 41.67%)              6.00 ( 50.00%)
      Ops io-duration-2385M             116.00 (  0.00%)             21.00 ( 81.90%)             21.00 ( 81.90%)
      Ops io-duration-4055M             160.00 (  0.00%)             36.00 ( 77.50%)             35.00 ( 78.12%)
      Ops swaptotal-0M                    0.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swaptotal-715M             140138.00 (  0.00%)             18.00 ( 99.99%)             18.00 ( 99.99%)
      Ops swaptotal-2385M            385682.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swaptotal-4055M            418029.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-0M                       0.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-715M                   144.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-2385M               134227.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-4055M               125618.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops minorfaults-0M            1536429.00 (  0.00%)        1531632.00 (  0.31%)        1533541.00 (  0.19%)
      Ops minorfaults-715M          1786996.00 (  0.00%)        1612148.00 (  9.78%)        1608832.00 (  9.97%)
      Ops minorfaults-2385M         1757952.00 (  0.00%)        1614874.00 (  8.14%)        1613541.00 (  8.21%)
      Ops minorfaults-4055M         1774460.00 (  0.00%)        1633400.00 (  7.95%)        1630881.00 (  8.09%)
      Ops majorfaults-0M                  1.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops majorfaults-715M              184.00 (  0.00%)            167.00 (  9.24%)            166.00 (  9.78%)
      Ops majorfaults-2385M           24444.00 (  0.00%)            155.00 ( 99.37%)             93.00 ( 99.62%)
      Ops majorfaults-4055M           21357.00 (  0.00%)            147.00 ( 99.31%)            134.00 ( 99.37%)
      
      memcachetest is the transactions/second reported by memcachetest. In
              the vanilla kernel note that performance drops from around
              23K/sec to just over 4K/second when there is 2385M of IO going
              on in the background. With current mmotm, there is no collapse
      	in performance and with this follow-up series there is little
      	change.
      
      swaptotal is the total amount of swap traffic. With mmotm and the follow-up
      	series, the total amount of swapping is much reduced.
      
                                       3.9.0       3.9.0       3.9.0
                                     vanillamm1-mmotm-20130522mm1-lessdisrupt-v7r10
      Minor Faults                  11160152    10706748    10622316
      Major Faults                     46305         755         678
      Swap Ins                        260249           0           0
      Swap Outs                       683860          18          18
      Direct pages scanned                 0         678        2520
      Kswapd pages scanned           6046108     8814900     1639279
      Kswapd pages reclaimed         1081954     1172267     1094635
      Direct pages reclaimed               0         566        2304
      Kswapd efficiency                  17%         13%         66%
      Kswapd velocity               5217.560    7618.953    1414.879
      Direct efficiency                 100%         83%         91%
      Direct velocity                  0.000       0.586       2.175
      Percentage direct scans             0%          0%          0%
      Zone normal velocity          5105.086    6824.681     671.158
      Zone dma32 velocity            112.473     794.858     745.896
      Zone dma velocity                0.000       0.000       0.000
      Page writes by reclaim     1929612.000 6861768.000   32821.000
      Page writes file               1245752     6861750       32803
      Page writes anon                683860          18          18
      Page reclaim immediate            7484          40         239
      Sector Reads                   1130320       93996       86900
      Sector Writes                 13508052    10823500    11804436
      Page rescued immediate               0           0           0
      Slabs scanned                    33536       27136       18560
      Direct inode steals                  0           0           0
      Kswapd inode steals               8641        1035           0
      Kswapd skipped wait                  0           0           0
      THP fault alloc                      8          37          33
      THP collapse alloc                 508         552         515
      THP splits                          24           1           1
      THP fault fallback                   0           0           0
      THP collapse fail                    0           0           0
      
      There are a number of observations to make here
      
      1. Swap outs are almost eliminated. Swap ins are 0 indicating that the
         pages swapped were really unused anonymous pages. Related to that,
         major faults are much reduced.
      
      2. kswapd efficiency was impacted by the initial series but with these
         follow-up patches, the efficiency is now at 66% indicating that far
         fewer pages were skipped during scanning due to dirty or writeback
         pages.
      
      3. kswapd velocity is reduced indicating that fewer pages are being scanned
         with the follow-up series as kswapd now stalls when the tail of the
         LRU queue is full of unqueued dirty pages. The stall gives flushers a
         chance to catch-up so kswapd can reclaim clean pages when it wakes
      
      4. In light of Zlatko's recent reports about zone scanning imbalances,
         mmtests now reports scanning velocity on a per-zone basis. With mainline,
         you can see that the scanning activity is dominated by the Normal
         zone with over 45 times more scanning in Normal than the DMA32 zone.
         With the series currently in mmotm, the ratio is slightly better but it
         is still the case that the bulk of scanning is in the highest zone. With
         this follow-up series, the ratio of scanning between the Normal and
         DMA32 zone is roughly equal.
      
      5. As Dave Chinner observed, the current patches in mmotm increased the
         number of pages written from kswapd context which is expected to adversly
         impact IO performance. With the follow-up patches, far fewer pages are
         written from kswapd context than the mainline kernel
      
      6. With the series in mmotm, fewer inodes were reclaimed by kswapd. With
         the follow-up series, there is less slab shrinking activity and no inodes
         were reclaimed.
      
      7. Note that "Sectors Read" is drastically reduced implying that the source
         data being used for the IO is not being aggressively discarded due to
         page reclaim skipping over dirty pages and reclaiming clean pages. Note
         that the reducion in reads could also be due to inode data not being
         re-read from disk after a slab shrink.
      
                             3.9.0       3.9.0       3.9.0
                           vanillamm1-mmotm-20130522mm1-lessdisrupt-v7r10
      Mean sda-avgqz        166.99       32.09       33.44
      Mean sda-await        853.64      192.76      185.43
      Mean sda-r_await        6.31        9.24        5.97
      Mean sda-w_await     2992.81      202.65      192.43
      Max  sda-avgqz       1409.91      718.75      698.98
      Max  sda-await       6665.74     3538.00     3124.23
      Max  sda-r_await       58.96      111.95       58.00
      Max  sda-w_await    28458.94     3977.29     3148.61
      
      In light of the changes in writes from reclaim context, the number of
      reads and Dave Chinner's concerns about IO performance I took a closer
      look at the IO stats for the test disk. Few observations
      
      1. The average queue size is reduced by the initial series and roughly
         the same with this follow up.
      
      2. Average wait times for writes are reduced and as the IO
         is completing faster it at least implies that the gain is because
         flushers are writing the files efficiently instead of page reclaim
         getting in the way.
      
      3. The reduction in maximum write latency is staggering. 28 seconds down
         to 3 seconds.
      
      Jan Kara asked how NFS is affected by all of this. Unstable pages can
      be taken into account as one of the patches in the series shows but it
      is still the case that filesystems with unusual handling of dirty or
      writeback could still be treated better.
      
      Tests like postmark, fsmark and largedd showed up nothing useful. On my test
      setup, pages are simply not being written back from reclaim context with or
      without the patches and there are no changes in performance. My test setup
      probably is just not strong enough network-wise to be really interesting.
      
      I ran a longer-lived memcached test with IO going to NFS instead of a local disk
      
      parallelio
                                                   3.9.0                       3.9.0                       3.9.0
                                                 vanilla          mm1-mmotm-20130522       mm1-lessdisrupt-v7r10
      Ops memcachetest-0M             23323.00 (  0.00%)          23241.00 ( -0.35%)          23321.00 ( -0.01%)
      Ops memcachetest-715M           25526.00 (  0.00%)          24763.00 ( -2.99%)          23242.00 ( -8.95%)
      Ops memcachetest-2385M           8814.00 (  0.00%)          26924.00 (205.47%)          23521.00 (166.86%)
      Ops memcachetest-4055M           5835.00 (  0.00%)          26827.00 (359.76%)          25560.00 (338.05%)
      Ops io-duration-0M                  0.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops io-duration-715M               65.00 (  0.00%)             71.00 ( -9.23%)             11.00 ( 83.08%)
      Ops io-duration-2385M             129.00 (  0.00%)             94.00 ( 27.13%)             53.00 ( 58.91%)
      Ops io-duration-4055M             301.00 (  0.00%)            100.00 ( 66.78%)            108.00 ( 64.12%)
      Ops swaptotal-0M                    0.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swaptotal-715M              14394.00 (  0.00%)            949.00 ( 93.41%)             63.00 ( 99.56%)
      Ops swaptotal-2385M            401483.00 (  0.00%)          24437.00 ( 93.91%)          30118.00 ( 92.50%)
      Ops swaptotal-4055M            554123.00 (  0.00%)          35688.00 ( 93.56%)          63082.00 ( 88.62%)
      Ops swapin-0M                       0.00 (  0.00%)              0.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-715M                  4522.00 (  0.00%)            560.00 ( 87.62%)             63.00 ( 98.61%)
      Ops swapin-2385M               169861.00 (  0.00%)           5026.00 ( 97.04%)          13917.00 ( 91.81%)
      Ops swapin-4055M               192374.00 (  0.00%)          10056.00 ( 94.77%)          25729.00 ( 86.63%)
      Ops minorfaults-0M            1445969.00 (  0.00%)        1520878.00 ( -5.18%)        1454024.00 ( -0.56%)
      Ops minorfaults-715M          1557288.00 (  0.00%)        1528482.00 (  1.85%)        1535776.00 (  1.38%)
      Ops minorfaults-2385M         1692896.00 (  0.00%)        1570523.00 (  7.23%)        1559622.00 (  7.87%)
      Ops minorfaults-4055M         1654985.00 (  0.00%)        1581456.00 (  4.44%)        1596713.00 (  3.52%)
      Ops majorfaults-0M                  0.00 (  0.00%)              1.00 (-99.00%)              0.00 (  0.00%)
      Ops majorfaults-715M              763.00 (  0.00%)            265.00 ( 65.27%)             75.00 ( 90.17%)
      Ops majorfaults-2385M           23861.00 (  0.00%)            894.00 ( 96.25%)           2189.00 ( 90.83%)
      Ops majorfaults-4055M           27210.00 (  0.00%)           1569.00 ( 94.23%)           4088.00 ( 84.98%)
      
      1. Performance does not collapse due to IO which is good. IO is also completing
         faster. Note with mmotm, IO completes in a third of the time and faster again
         with this series applied
      
      2. Swapping is reduced, although not eliminated. The figures for the follow-up
         look bad but it does vary a bit as the stalling is not perfect for nfs
         or filesystems like ext3 with unusual handling of dirty and writeback
         pages
      
      3. There are swapins, particularly with larger amounts of IO indicating
         that active pages are being reclaimed. However, the number of much
         reduced.
      
                                       3.9.0       3.9.0       3.9.0
                                     vanillamm1-mmotm-20130522mm1-lessdisrupt-v7r10
      Minor Faults                  36339175    35025445    35219699
      Major Faults                    310964       27108       51887
      Swap Ins                       2176399      173069      333316
      Swap Outs                      3344050      357228      504824
      Direct pages scanned              8972       77283       43242
      Kswapd pages scanned          20899983     8939566    14772851
      Kswapd pages reclaimed         6193156     5172605     5231026
      Direct pages reclaimed            8450       73802       39514
      Kswapd efficiency                  29%         57%         35%
      Kswapd velocity               3929.743    1847.499    3058.840
      Direct efficiency                  94%         95%         91%
      Direct velocity                  1.687      15.972       8.954
      Percentage direct scans             0%          0%          0%
      Zone normal velocity          3721.907     939.103    2185.142
      Zone dma32 velocity            209.522     924.368     882.651
      Zone dma velocity                0.000       0.000       0.000
      Page writes by reclaim     4082185.000  526319.000  537114.000
      Page writes file                738135      169091       32290
      Page writes anon               3344050      357228      504824
      Page reclaim immediate            9524         170     5595843
      Sector Reads                   8909900      861192     1483680
      Sector Writes                 13428980     1488744     2076800
      Page rescued immediate               0           0           0
      Slabs scanned                    38016       31744       28672
      Direct inode steals                  0           0           0
      Kswapd inode steals                424           0           0
      Kswapd skipped wait                  0           0           0
      THP fault alloc                     14          15         119
      THP collapse alloc                1767        1569        1618
      THP splits                          30          29          25
      THP fault fallback                   0           0           0
      THP collapse fail                    8           5           0
      Compaction stalls                   17          41         100
      Compaction success                   7          31          95
      Compaction failures                 10          10           5
      Page migrate success              7083       22157       62217
      Page migrate failure                 0           0           0
      Compaction pages isolated        14847       48758      135830
      Compaction migrate scanned       18328       48398      138929
      Compaction free scanned        2000255      355827     1720269
      Compaction cost                      7          24          68
      
      I guess the main takeaway again is the much reduced page writes
      from reclaim context and reduced reads.
      
                             3.9.0       3.9.0       3.9.0
                           vanillamm1-mmotm-20130522mm1-lessdisrupt-v7r10
      Mean sda-avgqz         23.58        0.35        0.44
      Mean sda-await        133.47       15.72       15.46
      Mean sda-r_await        4.72        4.69        3.95
      Mean sda-w_await      507.69       28.40       33.68
      Max  sda-avgqz        680.60       12.25       23.14
      Max  sda-await       3958.89      221.83      286.22
      Max  sda-r_await       63.86       61.23       67.29
      Max  sda-w_await    11710.38      883.57     1767.28
      
      And as before, write wait times are much reduced.
      
      This patch:
      
      The patch "mm: vmscan: Have kswapd writeback pages based on dirty pages
      encountered, not priority" decides whether to writeback pages from reclaim
      context based on the number of dirty pages encountered.  This situation is
      flagged too easily and flushers are not given the chance to catch up
      resulting in more pages being written from reclaim context and potentially
      impacting IO performance.  The check for PageWriteback is also misplaced
      as it happens within a PageDirty check which is nonsense as the dirty may
      have been cleared for IO.  The accounting is updated very late and pages
      that are already under writeback, were reactivated, could not unmapped or
      could not be released are all missed.  Similarly, a page is considered
      congested for reasons other than being congested and pages that cannot be
      written out in the correct context are skipped.  Finally, it considers
      stalling and writing back filesystem pages due to encountering dirty
      anonymous pages at the tail of the LRU which is dumb.
      
      This patch causes kswapd to begin writing filesystem pages from reclaim
      context only if page reclaim found that all filesystem pages at the tail
      of the LRU were unqueued dirty pages.  Before it starts writing filesystem
      pages, it will stall to give flushers a chance to catch up.  The decision
      on whether wait_iff_congested is also now determined by dirty filesystem
      pages only.  Congested pages are based on whether the underlying BDI is
      congested regardless of the context of the reclaiming process.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Cc: Zlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e2be15f6
    • M
      mm: vmscan: move logic from balance_pgdat() to kswapd_shrink_zone() · 7c954f6d
      Mel Gorman 提交于
      balance_pgdat() is very long and some of the logic can and should be
      internal to kswapd_shrink_zone().  Move it so the flow of
      balance_pgdat() is marginally easier to follow.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NRik van Riel <riel@redhat.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      7c954f6d
    • M
      mm: vmscan: check if kswapd should writepage once per pgdat scan · b7ea3c41
      Mel Gorman 提交于
      Currently kswapd checks if it should start writepage as it shrinks each
      zone without taking into consideration if the zone is balanced or not.
      This is not wrong as such but it does not make much sense either.  This
      patch checks once per pgdat scan if kswapd should be writing pages.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NRik van Riel <riel@redhat.com>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b7ea3c41
    • M
      mm: vmscan: block kswapd if it is encountering pages under writeback · 283aba9f
      Mel Gorman 提交于
      Historically, kswapd used to congestion_wait() at higher priorities if
      it was not making forward progress.  This made no sense as the failure
      to make progress could be completely independent of IO.  It was later
      replaced by wait_iff_congested() and removed entirely by commit 258401a6
      (mm: don't wait on congested zones in balance_pgdat()) as it was
      duplicating logic in shrink_inactive_list().
      
      This is problematic.  If kswapd encounters many pages under writeback
      and it continues to scan until it reaches the high watermark then it
      will quickly skip over the pages under writeback and reclaim clean young
      pages or push applications out to swap.
      
      The use of wait_iff_congested() is not suited to kswapd as it will only
      stall if the underlying BDI is really congested or a direct reclaimer
      was unable to write to the underlying BDI.  kswapd bypasses the BDI
      congestion as it sets PF_SWAPWRITE but even if this was taken into
      account then it would cause direct reclaimers to stall on writeback
      which is not desirable.
      
      This patch sets a ZONE_WRITEBACK flag if direct reclaim or kswapd is
      encountering too many pages under writeback.  If this flag is set and
      kswapd encounters a PageReclaim page under writeback then it'll assume
      that the LRU lists are being recycled too quickly before IO can complete
      and block waiting for some IO to complete.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NRik van Riel <riel@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      283aba9f
    • M
      mm: vmscan: have kswapd writeback pages based on dirty pages encountered, not priority · d43006d5
      Mel Gorman 提交于
      Currently kswapd queues dirty pages for writeback if scanning at an
      elevated priority but the priority kswapd scans at is not related to the
      number of unqueued dirty encountered.  Since commit "mm: vmscan: Flatten
      kswapd priority loop", the priority is related to the size of the LRU
      and the zone watermark which is no indication as to whether kswapd
      should write pages or not.
      
      This patch tracks if an excessive number of unqueued dirty pages are
      being encountered at the end of the LRU.  If so, it indicates that dirty
      pages are being recycled before flusher threads can clean them and flags
      the zone so that kswapd will start writing pages until the zone is
      balanced.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d43006d5
    • M
      mm: vmscan: do not allow kswapd to scan at maximum priority · 9aa41348
      Mel Gorman 提交于
      Page reclaim at priority 0 will scan the entire LRU as priority 0 is
      considered to be a near OOM condition.  Kswapd can reach priority 0
      quite easily if it is encountering a large number of pages it cannot
      reclaim such as pages under writeback.  When this happens, kswapd
      reclaims very aggressively even though there may be no real risk of
      allocation failure or OOM.
      
      This patch prevents kswapd reaching priority 0 and trying to reclaim the
      world.  Direct reclaimers will still reach priority 0 in the event of an
      OOM situation.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Acked-by: NRik van Riel <riel@redhat.com>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9aa41348
    • M
      mm: vmscan: decide whether to compact the pgdat based on reclaim progress · 2ab44f43
      Mel Gorman 提交于
      In the past, kswapd makes a decision on whether to compact memory after
      the pgdat was considered balanced.  This more or less worked but it is
      late to make such a decision and does not fit well now that kswapd makes
      a decision whether to exit the zone scanning loop depending on reclaim
      progress.
      
      This patch will compact a pgdat if at least the requested number of
      pages were reclaimed from unbalanced zones for a given priority.  If any
      zone is currently balanced, kswapd will not call compaction as it is
      expected the necessary pages are already available.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2ab44f43
    • M
      mm: vmscan: flatten kswapd priority loop · b8e83b94
      Mel Gorman 提交于
      kswapd stops raising the scanning priority when at least
      SWAP_CLUSTER_MAX pages have been reclaimed or the pgdat is considered
      balanced.  It then rechecks if it needs to restart at DEF_PRIORITY and
      whether high-order reclaim needs to be reset.  This is not wrong per-se
      but it is confusing to follow and forcing kswapd to stay at DEF_PRIORITY
      may require several restarts before it has scanned enough pages to meet
      the high watermark even at 100% efficiency.  This patch irons out the
      logic a bit by controlling when priority is raised and removing the
      "goto loop_again".
      
      This patch has kswapd raise the scanning priority until it is scanning
      enough pages that it could meet the high watermark in one shrink of the
      LRU lists if it is able to reclaim at 100% efficiency.  It will not
      raise the scanning prioirty higher unless it is failing to reclaim any
      pages.
      
      To avoid infinite looping for high-order allocation requests kswapd will
      not reclaim for high-order allocations when it has reclaimed at least
      twice the number of pages as the allocation request.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b8e83b94
    • M
      mm: vmscan: obey proportional scanning requirements for kswapd · e82e0561
      Mel Gorman 提交于
      Simplistically, the anon and file LRU lists are scanned proportionally
      depending on the value of vm.swappiness although there are other factors
      taken into account by get_scan_count().  The patch "mm: vmscan: Limit
      the number of pages kswapd reclaims" limits the number of pages kswapd
      reclaims but it breaks this proportional scanning and may evenly shrink
      anon/file LRUs regardless of vm.swappiness.
      
      This patch preserves the proportional scanning and reclaim.  It does
      mean that kswapd will reclaim more than requested but the number of
      pages will be related to the high watermark.
      
      [mhocko@suse.cz: Correct proportional reclaim for memcg and simplify]
      [kamezawa.hiroyu@jp.fujitsu.com: Recalculate scan based on target]
      [hannes@cmpxchg.org: Account for already scanned pages properly]
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Acked-by: NRik van Riel <riel@redhat.com>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e82e0561
    • M
      mm: vmscan: limit the number of pages kswapd reclaims at each priority · 75485363
      Mel Gorman 提交于
      This series does not fix all the current known problems with reclaim but
      it addresses one important swapping bug when there is background IO.
      
      Changelog since V3
       - Drop the slab shrink changes in light of Glaubers series and
         discussions highlighted that there were a number of potential
         problems with the patch.					(mel)
       - Rebased to 3.10-rc1
      
      Changelog since V2
       - Preserve ratio properly for proportional scanning		(kamezawa)
      
      Changelog since V1
       - Rename ZONE_DIRTY to ZONE_TAIL_LRU_DIRTY			(andi)
       - Reformat comment in shrink_page_list				(andi)
       - Clarify some comments					(dhillf)
       - Rework how the proportional scanning is preserved
       - Add PageReclaim check before kswapd starts writeback
       - Reset sc.nr_reclaimed on every full zone scan
      
      Kswapd and page reclaim behaviour has been screwy in one way or the
      other for a long time.  Very broadly speaking it worked in the far past
      because machines were limited in memory so it did not have that many
      pages to scan and it stalled congestion_wait() frequently to prevent it
      going completely nuts.  In recent times it has behaved very
      unsatisfactorily with some of the problems compounded by the removal of
      stall logic and the introduction of transparent hugepage support with
      high-order reclaims.
      
      There are many variations of bugs that are rooted in this area.  One
      example is reports of a large copy operations or backup causing the
      machine to grind to a halt or applications pushed to swap.  Sometimes in
      low memory situations a large percentage of memory suddenly gets
      reclaimed.  In other cases an application starts and kswapd hits 100%
      CPU usage for prolonged periods of time and so on.  There is now talk of
      introducing features like an extra free kbytes tunable to work around
      aspects of the problem instead of trying to deal with it.  It's
      compounded by the problem that it can be very workload and machine
      specific.
      
      This series aims at addressing some of the worst of these problems
      without attempting to fundmentally alter how page reclaim works.
      
      Patches 1-2 limits the number of pages kswapd reclaims while still obeying
      	the anon/file proportion of the LRUs it should be scanning.
      
      Patches 3-4 control how and when kswapd raises its scanning priority and
      	deletes the scanning restart logic which is tricky to follow.
      
      Patch 5 notes that it is too easy for kswapd to reach priority 0 when
      	scanning and then reclaim the world. Down with that sort of thing.
      
      Patch 6 notes that kswapd starts writeback based on scanning priority which
      	is not necessarily related to dirty pages. It will have kswapd
      	writeback pages if a number of unqueued dirty pages have been
      	recently encountered at the tail of the LRU.
      
      Patch 7 notes that sometimes kswapd should stall waiting on IO to complete
      	to reduce LRU churn and the likelihood that it'll reclaim young
      	clean pages or push applications to swap. It will cause kswapd
      	to block on IO if it detects that pages being reclaimed under
      	writeback are recycling through the LRU before the IO completes.
      
      Patchies 8-9 are cosmetic but balance_pgdat() is easier to follow after they
      	are applied.
      
      This was tested using memcached+memcachetest while some background IO
      was in progress as implemented by the parallel IO tests implement in MM
      Tests.
      
      memcachetest benchmarks how many operations/second memcached can service
      and it is run multiple times.  It starts with no background IO and then
      re-runs the test with larger amounts of IO in the background to roughly
      simulate a large copy in progress.  The expectation is that the IO
      should have little or no impact on memcachetest which is running
      entirely in memory.
      
                                              3.10.0-rc1                  3.10.0-rc1
                                                 vanilla            lessdisrupt-v4
      Ops memcachetest-0M             22155.00 (  0.00%)          22180.00 (  0.11%)
      Ops memcachetest-715M           22720.00 (  0.00%)          22355.00 ( -1.61%)
      Ops memcachetest-2385M           3939.00 (  0.00%)          23450.00 (495.33%)
      Ops memcachetest-4055M           3628.00 (  0.00%)          24341.00 (570.92%)
      Ops io-duration-0M                  0.00 (  0.00%)              0.00 (  0.00%)
      Ops io-duration-715M               12.00 (  0.00%)              7.00 ( 41.67%)
      Ops io-duration-2385M             118.00 (  0.00%)             21.00 ( 82.20%)
      Ops io-duration-4055M             162.00 (  0.00%)             36.00 ( 77.78%)
      Ops swaptotal-0M                    0.00 (  0.00%)              0.00 (  0.00%)
      Ops swaptotal-715M             140134.00 (  0.00%)             18.00 ( 99.99%)
      Ops swaptotal-2385M            392438.00 (  0.00%)              0.00 (  0.00%)
      Ops swaptotal-4055M            449037.00 (  0.00%)          27864.00 ( 93.79%)
      Ops swapin-0M                       0.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-715M                     0.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-2385M               148031.00 (  0.00%)              0.00 (  0.00%)
      Ops swapin-4055M               135109.00 (  0.00%)              0.00 (  0.00%)
      Ops minorfaults-0M            1529984.00 (  0.00%)        1530235.00 ( -0.02%)
      Ops minorfaults-715M          1794168.00 (  0.00%)        1613750.00 ( 10.06%)
      Ops minorfaults-2385M         1739813.00 (  0.00%)        1609396.00 (  7.50%)
      Ops minorfaults-4055M         1754460.00 (  0.00%)        1614810.00 (  7.96%)
      Ops majorfaults-0M                  0.00 (  0.00%)              0.00 (  0.00%)
      Ops majorfaults-715M              185.00 (  0.00%)            180.00 (  2.70%)
      Ops majorfaults-2385M           24472.00 (  0.00%)            101.00 ( 99.59%)
      Ops majorfaults-4055M           22302.00 (  0.00%)            229.00 ( 98.97%)
      
      Note how the vanilla kernels performance collapses when there is enough
      IO taking place in the background.  This drop in performance is part of
      what users complain of when they start backups.  Note how the swapin and
      major fault figures indicate that processes were being pushed to swap
      prematurely.  With the series applied, there is no noticable performance
      drop and while there is still some swap activity, it's tiny.
      
      20 iterations of this test were run in total and averaged.  Every 5
      iterations, additional IO was generated in the background using dd to
      measure how the workload was impacted.  The 0M, 715M, 2385M and 4055M
      subblock refer to the amount of IO going on in the background at each
      iteration.  So memcachetest-2385M is reporting how many
      transactions/second memcachetest recorded on average over 5 iterations
      while there was 2385M of IO going on in the ground.  There are six
      blocks of information reported here
      
      memcachetest is the transactions/second reported by memcachetest. In
      	the vanilla kernel note that performance drops from around
      	22K/sec to just under 4K/second when there is 2385M of IO going
      	on in the background. This is one type of performance collapse
      	users complain about if a large cp or backup starts in the
      	background
      
      io-duration refers to how long it takes for the background IO to
      	complete. It's showing that with the patched kernel that the IO
      	completes faster while not interfering with the memcache
      	workload
      
      swaptotal is the total amount of swap traffic. With the patched kernel,
      	the total amount of swapping is much reduced although it is
      	still not zero.
      
      swapin in this case is an indication as to whether we are swap trashing.
      	The closer the swapin/swapout ratio is to 1, the worse the
      	trashing is.  Note with the patched kernel that there is no swapin
      	activity indicating that all the pages swapped were really inactive
      	unused pages.
      
      minorfaults are just minor faults. An increased number of minor faults
      	can indicate that page reclaim is unmapping the pages but not
      	swapping them out before they are faulted back in. With the
      	patched kernel, there is only a small change in minor faults
      
      majorfaults are just major faults in the target workload and a high
      	number can indicate that a workload is being prematurely
      	swapped. With the patched kernel, major faults are much reduced. As
      	there are no swapin's recorded so it's not being swapped. The likely
      	explanation is that that libraries or configuration files used by
      	the workload during startup get paged out by the background IO.
      
      Overall with the series applied, there is no noticable performance drop
      due to background IO and while there is still some swap activity, it's
      tiny and the lack of swapins imply that the swapped pages were inactive
      and unused.
      
                                  3.10.0-rc1  3.10.0-rc1
                                     vanilla lessdisrupt-v4
      Page Ins                       1234608      101892
      Page Outs                     12446272    11810468
      Swap Ins                        283406           0
      Swap Outs                       698469       27882
      Direct pages scanned                 0      136480
      Kswapd pages scanned           6266537     5369364
      Kswapd pages reclaimed         1088989      930832
      Direct pages reclaimed               0      120901
      Kswapd efficiency                  17%         17%
      Kswapd velocity               5398.371    4635.115
      Direct efficiency                 100%         88%
      Direct velocity                  0.000     117.817
      Percentage direct scans             0%          2%
      Page writes by reclaim         1655843     4009929
      Page writes file                957374     3982047
      Page writes anon                698469       27882
      Page reclaim immediate            5245        1745
      Page rescued immediate               0           0
      Slabs scanned                    33664       25216
      Direct inode steals                  0           0
      Kswapd inode steals              19409         778
      Kswapd skipped wait                  0           0
      THP fault alloc                     35          30
      THP collapse alloc                 472         401
      THP splits                          27          22
      THP fault fallback                   0           0
      THP collapse fail                    0           1
      Compaction stalls                    0           4
      Compaction success                   0           0
      Compaction failures                  0           4
      Page migrate success                 0           0
      Page migrate failure                 0           0
      Compaction pages isolated            0           0
      Compaction migrate scanned           0           0
      Compaction free scanned              0           0
      Compaction cost                      0           0
      NUMA PTE updates                     0           0
      NUMA hint faults                     0           0
      NUMA hint local faults               0           0
      NUMA pages migrated                  0           0
      AutoNUMA cost                        0           0
      
      Unfortunately, note that there is a small amount of direct reclaim due to
      kswapd no longer reclaiming the world.  ftrace indicates that the direct
      reclaim stalls are mostly harmless with the vast bulk of the stalls
      incurred by dd
      
           23 tclsh-3367
           38 memcachetest-13733
           49 memcachetest-12443
           57 tee-3368
         1541 dd-13826
         1981 dd-12539
      
      A consequence of the direct reclaim for dd is that the processes for the
      IO workload may show a higher system CPU usage.  There is also a risk that
      kswapd not reclaiming the world may mean that it stays awake balancing
      zones, does not stall on the appropriate events and continually scans
      pages it cannot reclaim consuming CPU.  This will be visible as continued
      high CPU usage but in my own tests I only saw a single spike lasting less
      than a second and I did not observe any problems related to reclaim while
      running the series on my desktop.
      
      This patch:
      
      The number of pages kswapd can reclaim is bound by the number of pages it
      scans which is related to the size of the zone and the scanning priority.
      In many cases the priority remains low because it's reset every
      SWAP_CLUSTER_MAX reclaimed pages but in the event kswapd scans a large
      number of pages it cannot reclaim, it will raise the priority and
      potentially discard a large percentage of the zone as sc->nr_to_reclaim is
      ULONG_MAX.  The user-visible effect is a reclaim "spike" where a large
      percentage of memory is suddenly freed.  It would be bad enough if this
      was just unused memory but because of how anon/file pages are balanced it
      is possible that applications get pushed to swap unnecessarily.
      
      This patch limits the number of pages kswapd will reclaim to the high
      watermark.  Reclaim will still overshoot due to it not being a hard limit
      as shrink_lruvec() will ignore the sc.nr_to_reclaim at DEF_PRIORITY but it
      prevents kswapd reclaiming the world at higher priorities.  The number of
      pages it reclaims is not adjusted for high-order allocations as kswapd
      will reclaim excessively if it is to balance zones for high-order
      allocations.
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NRik van Riel <riel@redhat.com>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
      Tested-by: NZlatko Calusic <zcalusic@bitsync.net>
      Cc: dormando <dormando@rydia.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      75485363
  4. 30 4月, 2013 3 次提交
    • S
      mm: thp: add split tail pages to shrink page list in page reclaim · 5bc7b8ac
      Shaohua Li 提交于
      In page reclaim, huge page is split.  split_huge_page() adds tail pages
      to LRU list.  Since we are reclaiming a huge page, it's better we
      reclaim all subpages of the huge page instead of just the head page.
      This patch adds split tail pages to shrink page list so the tail pages
      can be reclaimed soon.
      
      Before this patch, run a swap workload:
        thp_fault_alloc 3492
        thp_fault_fallback 608
        thp_collapse_alloc 6
        thp_collapse_alloc_failed 0
        thp_split 916
      
      With this patch:
        thp_fault_alloc 4085
        thp_fault_fallback 16
        thp_collapse_alloc 90
        thp_collapse_alloc_failed 0
        thp_split 1272
      
      fallback allocation is reduced a lot.
      
      [akpm@linux-foundation.org: fix CONFIG_SWAP=n build]
      Signed-off-by: NShaohua Li <shli@fusionio.com>
      Acked-by: NRik van Riel <riel@redhat.com>
      Acked-by: NMinchan Kim <minchan@kernel.org>
      Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NWanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Hugh Dickins <hughd@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5bc7b8ac
    • A
      memcg: add memory.pressure_level events · 70ddf637
      Anton Vorontsov 提交于
      With this patch userland applications that want to maintain the
      interactivity/memory allocation cost can use the pressure level
      notifications.  The levels are defined like this:
      
      The "low" level means that the system is reclaiming memory for new
      allocations.  Monitoring this reclaiming activity might be useful for
      maintaining cache level.  Upon notification, the program (typically
      "Activity Manager") might analyze vmstat and act in advance (i.e.
      prematurely shutdown unimportant services).
      
      The "medium" level means that the system is experiencing medium memory
      pressure, the system might be making swap, paging out active file
      caches, etc.  Upon this event applications may decide to further analyze
      vmstat/zoneinfo/memcg or internal memory usage statistics and free any
      resources that can be easily reconstructed or re-read from a disk.
      
      The "critical" level means that the system is actively thrashing, it is
      about to out of memory (OOM) or even the in-kernel OOM killer is on its
      way to trigger.  Applications should do whatever they can to help the
      system.  It might be too late to consult with vmstat or any other
      statistics, so it's advisable to take an immediate action.
      
      The events are propagated upward until the event is handled, i.e.  the
      events are not pass-through.  Here is what this means: for example you
      have three cgroups: A->B->C.  Now you set up an event listener on
      cgroups A, B and C, and suppose group C experiences some pressure.  In
      this situation, only group C will receive the notification, i.e.  groups
      A and B will not receive it.  This is done to avoid excessive
      "broadcasting" of messages, which disturbs the system and which is
      especially bad if we are low on memory or thrashing.  So, organize the
      cgroups wisely, or propagate the events manually (or, ask us to
      implement the pass-through events, explaining why would you need them.)
      
      Performance wise, the memory pressure notifications feature itself is
      lightweight and does not require much of bookkeeping, in contrast to the
      rest of memcg features.  Unfortunately, as of current memcg
      implementation, pages accounting is an inseparable part and cannot be
      turned off.  The good news is that there are some efforts[1] to improve
      the situation; plus, implementing the same, fully API-compatible[2]
      interface for CONFIG_MEMCG=n case (e.g.  embedded) is also a viable
      option, so it will not require any changes on the userland side.
      
      [1] http://permalink.gmane.org/gmane.linux.kernel.cgroups/6291
      [2] http://lkml.org/lkml/2013/2/21/454
      
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: fix CONFIG_CGROPUPS=n warnings]
      Signed-off-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
      Acked-by: NKirill A. Shutemov <kirill@shutemov.name>
      Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Glauber Costa <glommer@parallels.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Luiz Capitulino <lcapitulino@redhat.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: Leonid Moiseichuk <leonid.moiseichuk@nokia.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
      Cc: John Stultz <john.stultz@linaro.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      70ddf637
    • H
      mm/vmscan.c: minor cleanup for kswapd · 2d42a40d
      Hillf Danton 提交于
      Local variable total_scanned is no longer used.
      Signed-off-by: NHillf Danton <dhillf@gmail.com>
      Acked-by: NRik van Riel <riel@redhat.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2d42a40d
  5. 18 4月, 2013 1 次提交
  6. 24 2月, 2013 16 次提交
    • Z
      vmscan: change type of vm_total_pages to unsigned long · b21e0b90
      Zhang Yanfei 提交于
      This variable is calculated from nr_free_pagecache_pages so
      change its type to unsigned long.
      Signed-off-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b21e0b90
    • M
      mm: use up free swap space before reaching OOM kill · 0e50ce3b
      Minchan Kim 提交于
      Recently, Luigi reported there are lots of free swap space when OOM
      happens.  It's easily reproduced on zram-over-swap, where many instance
      of memory hogs are running and laptop_mode is enabled.  He said there
      was no problem when he disabled laptop_mode.  The problem when I
      investigate problem is following as.
      
      Assumption for easy explanation: There are no page cache page in system
      because they all are already reclaimed.
      
      1. try_to_free_pages disable may_writepage when laptop_mode is enabled.
      2. shrink_inactive_list isolates victim pages from inactive anon lru list.
      3. shrink_page_list adds them to swapcache via add_to_swap but it doesn't
         pageout because sc->may_writepage is 0 so the page is rotated back into
         inactive anon lru list. The add_to_swap made the page Dirty by SetPageDirty.
      4. 3 couldn't reclaim any pages so do_try_to_free_pages increase priority and
         retry reclaim with higher priority.
      5. shrink_inactlive_list try to isolate victim pages from inactive anon lru list
         but got failed because it try to isolate pages with ISOLATE_CLEAN mode but
         inactive anon lru list is full of dirty pages by 3 so it just returns
         without  any reclaim progress.
      6. do_try_to_free_pages doesn't set may_writepage due to zero total_scanned.
         Because sc->nr_scanned is increased by shrink_page_list but we don't call
         shrink_page_list in 5 due to short of isolated pages.
      
      Above loop is continued until OOM happens.
      
      The problem didn't happen before [1] was merged because old logic's
      isolatation in shrink_inactive_list was successful and tried to call
      shrink_page_list to pageout them but it still ends up failed to page out
      by may_writepage.  But important point is that sc->nr_scanned was
      increased although we couldn't swap out them so do_try_to_free_pages
      could set may_writepages.
      
      Since commit f80c0673 ("mm: zone_reclaim: make isolate_lru_page()
      filter-aware") was introduced, it's not a good idea any more to depends
      on only the number of scanned pages for setting may_writepage.  So this
      patch adds new trigger point of setting may_writepage as below
      DEF_PRIOIRTY - 2 which is used to show the significant memory pressure
      in VM so it's good fit for our purpose which would be better to lose
      power saving or clickety rather than OOM killing.
      Signed-off-by: NMinchan Kim <minchan@kernel.org>
      Reported-by: NLuigi Semenzato <semenzato@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0e50ce3b
    • J
      mm: refactor inactive_file_is_low() to use get_lru_size() · e3790144
      Johannes Weiner 提交于
      An inactive file list is considered low when its active counterpart is
      bigger, regardless of whether it is a global zone LRU list or a memcg
      zone LRU list.  The only difference is in how the LRU size is assessed.
      
      get_lru_size() does the right thing for both global and memcg reclaim
      situations.
      
      Get rid of inactive_file_is_low_global() and
      mem_cgroup_inactive_file_is_low() by using get_lru_size() and compare
      the numbers in common code.
      Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e3790144
    • S
      swap: add per-partition lock for swapfile · ec8acf20
      Shaohua Li 提交于
      swap_lock is heavily contended when I test swap to 3 fast SSD (even
      slightly slower than swap to 2 such SSD).  The main contention comes
      from swap_info_get().  This patch tries to fix the gap with adding a new
      per-partition lock.
      
      Global data like nr_swapfiles, total_swap_pages, least_priority and
      swap_list are still protected by swap_lock.
      
      nr_swap_pages is an atomic now, it can be changed without swap_lock.  In
      theory, it's possible get_swap_page() finds no swap pages but actually
      there are free swap pages.  But sounds not a big problem.
      
      Accessing partition specific data (like scan_swap_map and so on) is only
      protected by swap_info_struct.lock.
      
      Changing swap_info_struct.flags need hold swap_lock and
      swap_info_struct.lock, because scan_scan_map() will check it.  read the
      flags is ok with either the locks hold.
      
      If both swap_lock and swap_info_struct.lock must be hold, we always hold
      the former first to avoid deadlock.
      
      swap_entry_free() can change swap_list.  To delete that code, we add a
      new highest_priority_index.  Whenever get_swap_page() is called, we
      check it.  If it's valid, we use it.
      
      It's a pity get_swap_page() still holds swap_lock().  But in practice,
      swap_lock() isn't heavily contended in my test with this patch (or I can
      say there are other much more heavier bottlenecks like TLB flush).  And
      BTW, looks get_swap_page() doesn't really need the lock.  We never free
      swap_info[] and we check SWAP_WRITEOK flag.  The only risk without the
      lock is we could swapout to some low priority swap, but we can quickly
      recover after several rounds of swap, so sounds not a big deal to me.
      But I'd prefer to fix this if it's a real problem.
      
      "swap: make each swap partition have one address_space" improved the
      swapout speed from 1.7G/s to 2G/s.  This patch further improves the
      speed to 2.3G/s, so around 15% improvement.  It's a multi-process test,
      so TLB flush isn't the biggest bottleneck before the patches.
      
      [arnd@arndb.de: fix it for nommu]
      [hughd@google.com: add missing unlock]
      [minchan@kernel.org: get rid of lockdep whinge on sys_swapon]
      Signed-off-by: NShaohua Li <shli@fusionio.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
      Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: NArnd Bergmann <arnd@arndb.de>
      Signed-off-by: NHugh Dickins <hughd@google.com>
      Signed-off-by: NMinchan Kim <minchan@kernel.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ec8acf20
    • M
      mm: teach mm by current context info to not do I/O during memory allocation · 21caf2fc
      Ming Lei 提交于
      This patch introduces PF_MEMALLOC_NOIO on process flag('flags' field of
      'struct task_struct'), so that the flag can be set by one task to avoid
      doing I/O inside memory allocation in the task's context.
      
      The patch trys to solve one deadlock problem caused by block device, and
      the problem may happen at least in the below situations:
      
      - during block device runtime resume, if memory allocation with
        GFP_KERNEL is called inside runtime resume callback of any one of its
        ancestors(or the block device itself), the deadlock may be triggered
        inside the memory allocation since it might not complete until the block
        device becomes active and the involed page I/O finishes.  The situation
        is pointed out first by Alan Stern.  It is not a good approach to
        convert all GFP_KERNEL[1] in the path into GFP_NOIO because several
        subsystems may be involved(for example, PCI, USB and SCSI may be
        involved for usb mass stoarage device, network devices involved too in
        the iSCSI case)
      
      - during block device runtime suspend, because runtime resume need to
        wait for completion of concurrent runtime suspend.
      
      - during error handling of usb mass storage deivce, USB bus reset will
        be put on the device, so there shouldn't have any memory allocation with
        GFP_KERNEL during USB bus reset, otherwise the deadlock similar with
        above may be triggered.  Unfortunately, any usb device may include one
        mass storage interface in theory, so it requires all usb interface
        drivers to handle the situation.  In fact, most usb drivers don't know
        how to handle bus reset on the device and don't provide .pre_set() and
        .post_reset() callback at all, so USB core has to unbind and bind driver
        for these devices.  So it is still not practical to resort to GFP_NOIO
        for solving the problem.
      
      Also the introduced solution can be used by block subsystem or block
      drivers too, for example, set the PF_MEMALLOC_NOIO flag before doing
      actual I/O transfer.
      
      It is not a good idea to convert all these GFP_KERNEL in the affected
      path into GFP_NOIO because these functions doing that may be implemented
      as library and will be called in many other contexts.
      
      In fact, memalloc_noio_flags() can convert some of current static
      GFP_NOIO allocation into GFP_KERNEL back in other non-affected contexts,
      at least almost all GFP_NOIO in USB subsystem can be converted into
      GFP_KERNEL after applying the approach and make allocation with GFP_NOIO
      only happen in runtime resume/bus reset/block I/O transfer contexts
      generally.
      
      [1], several GFP_KERNEL allocation examples in runtime resume path
      
      - pci subsystem
      acpi_os_allocate
      	<-acpi_ut_allocate
      		<-ACPI_ALLOCATE_ZEROED
      			<-acpi_evaluate_object
      				<-__acpi_bus_set_power
      					<-acpi_bus_set_power
      						<-acpi_pci_set_power_state
      							<-platform_pci_set_power_state
      								<-pci_platform_power_transition
      									<-__pci_complete_power_transition
      										<-pci_set_power_state
      											<-pci_restore_standard_config
      												<-pci_pm_runtime_resume
      - usb subsystem
      usb_get_status
      	<-finish_port_resume
      		<-usb_port_resume
      			<-generic_resume
      				<-usb_resume_device
      					<-usb_resume_both
      						<-usb_runtime_resume
      
      - some individual usb drivers
      usblp, uvc, gspca, most of dvb-usb-v2 media drivers, cpia2, az6007, ....
      
      That is just what I have found.  Unfortunately, this allocation can only
      be found by human being now, and there should be many not found since
      any function in the resume path(call tree) may allocate memory with
      GFP_KERNEL.
      Signed-off-by: NMing Lei <ming.lei@canonical.com>
      Signed-off-by: NMinchan Kim <minchan@kernel.org>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Oliver Neukum <oneukum@suse.de>
      Cc: Jiri Kosina <jiri.kosina@suse.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Greg KH <greg@kroah.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Decotigny <david.decotigny@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      21caf2fc
    • Z
      mm: don't wait on congested zones in balance_pgdat() · 258401a6
      Zlatko Calusic 提交于
      From: Zlatko Calusic <zlatko.calusic@iskon.hr>
      
      Commit 92df3a72 ("mm: vmscan: throttle reclaim if encountering too
      many dirty pages under writeback") introduced waiting on congested zones
      based on a sane algorithm in shrink_inactive_list().
      
      What this means is that there's no more need for throttling and
      additional heuristics in balance_pgdat().  So, let's remove it and tidy
      up the code.
      Signed-off-by: NZlatko Calusic <zlatko.calusic@iskon.hr>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Cc: Johannes Weiner <jweiner@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      258401a6
    • J
      mm: use zone->present_pages instead of zone->managed_pages where appropriate · b40da049
      Jiang Liu 提交于
      Now we have zone->managed_pages for "pages managed by the buddy system
      in the zone", so replace zone->present_pages with zone->managed_pages if
      what the user really wants is number of allocatable pages.
      Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
      Cc: Wen Congyang <wency@cn.fujitsu.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Jiang Liu <jiang.liu@huawei.com>
      Cc: Maciej Rutecki <maciej.rutecki@gmail.com>
      Cc: Chris Clayton <chris2553@googlemail.com>
      Cc: "Rafael J . Wysocki" <rjw@sisk.pl>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Jianguo Wu <wujianguo@huawei.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b40da049
    • Z
      mm: avoid calling pgdat_balanced() needlessly · dafcb73e
      Zlatko Calusic 提交于
      Now that balance_pgdat() is slightly tidied up, thanks to more capable
      pgdat_balanced(), it's become obvious that pgdat_balanced() is called to
      check the status, then break the loop if pgdat is balanced, just to be
      immediately called again.  The second call is completely unnecessary, of
      course.
      
      The patch introduces pgdat_is_balanced boolean, which helps resolve the
      above suboptimal behavior, with the added benefit of slightly better
      documenting one other place in the function where we jump and skip lots
      of code.
      Signed-off-by: NZlatko Calusic <zlatko.calusic@iskon.hr>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      dafcb73e
    • M
      memcg,vmscan: do not break out targeted reclaim without reclaimed pages · a394cb8e
      Michal Hocko 提交于
      Targeted (hard resp soft) reclaim has traditionally tried to scan one
      group with decreasing priority until nr_to_reclaim (SWAP_CLUSTER_MAX
      pages) is reclaimed or all priorities are exhausted.  The reclaim is
      then retried until the limit is met.
      
      This approach, however, doesn't work well with deeper hierarchies where
      groups higher in the hierarchy do not have any or only very few pages
      (this usually happens if those groups do not have any tasks and they
      have only re-parented pages after some of their children is removed).
      Those groups are reclaimed with decreasing priority pointlessly as there
      is nothing to reclaim from them.
      
      An easiest fix is to break out of the memcg iteration loop in
      shrink_zone only if the whole hierarchy has been visited or sufficient
      pages have been reclaimed.  This is also more natural because the
      reclaimer expects that the hierarchy under the given root is reclaimed.
      As a result we can simplify the soft limit reclaim which does its own
      iteration.
      
      [yinghan@google.com: break out of the hierarchy loop only if nr_reclaimed exceeded nr_to_reclaim]
      [akpm@linux-foundation.org: use conventional comparison order]
      Signed-off-by: NMichal Hocko <mhocko@suse.cz>
      Reported-by: NYing Han <yinghan@google.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Tejun Heo <htejun@gmail.com>
      Cc: Glauber Costa <glommer@parallels.com>
      Cc: Li Zefan <lizefan@huawei.com>
      Signed-off-by: NYing Han <yinghan@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a394cb8e
    • A
      mm/vmscan.c:__zone_reclaim(): replace max_t() with max() · 62b726c1
      Andrew Morton 提交于
      "mm: vmscan: save work scanning (almost) empty LRU lists" made
      SWAP_CLUSTER_MAX an unsigned long.
      
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Satoru Moriya <satoru.moriya@hds.com>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      62b726c1
    • J
      mm: vmscan: compaction works against zones, not lruvecs · 9b4f98cd
      Johannes Weiner 提交于
      The restart logic for when reclaim operates back to back with compaction
      is currently applied on the lruvec level.  But this does not make sense,
      because the container of interest for compaction is a zone as a whole,
      not the zone pages that are part of a certain memory cgroup.
      
      Negative impact is bounded.  For one, the code checks that the lruvec
      has enough reclaim candidates, so it does not risk getting stuck on a
      condition that can not be fulfilled.  And the unfairness of hammering on
      one particular memory cgroup to make progress in a zone will be
      amortized by the round robin manner in which reclaim goes through the
      memory cgroups.  Still, this can lead to unnecessary allocation
      latencies when the code elects to restart on a hard to reclaim or small
      group when there are other, more reclaimable groups in the zone.
      
      Move this logic to the zone level and restart reclaim for all memory
      cgroups in a zone when compaction requires more free pages from it.
      
      [akpm@linux-foundation.org: no need for min_t]
      Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NRik van Riel <riel@redhat.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Satoru Moriya <satoru.moriya@hds.com>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9b4f98cd
    • J
      mm: vmscan: clean up get_scan_count() · 9a265114
      Johannes Weiner 提交于
      Reclaim pressure balance between anon and file pages is calculated
      through a tuple of numerators and a shared denominator.
      
      Exceptional cases that want to force-scan anon or file pages configure
      the numerators and denominator such that one list is preferred, which is
      not necessarily the most obvious way:
      
          fraction[0] = 1;
          fraction[1] = 0;
          denominator = 1;
          goto out;
      
      Make this easier by making the force-scan cases explicit and use the
      fractionals only in case they are calculated from reclaim history.
      
      [akpm@linux-foundation.org: avoid using unintialized_var()]
      Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NRik van Riel <riel@redhat.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Satoru Moriya <satoru.moriya@hds.com>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9a265114
    • J
      mm: vmscan: improve comment on low-page cache handling · 11d16c25
      Johannes Weiner 提交于
      Fix comment style and elaborate on why anonymous memory is force-scanned
      when file cache runs low.
      Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NRik van Riel <riel@redhat.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Satoru Moriya <satoru.moriya@hds.com>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      11d16c25
    • J
      mm: vmscan: clarify how swappiness, highest priority, memcg interact · 10316b31
      Johannes Weiner 提交于
      A swappiness of 0 has a slightly different meaning for global reclaim
      (may swap if file cache really low) and memory cgroup reclaim (never
      swap, ever).
      
      In addition, global reclaim at highest priority will scan all LRU lists
      equal to their size and ignore other balancing heuristics.  UNLESS
      swappiness forbids swapping, then the lists are balanced based on recent
      reclaim effectiveness.  UNLESS file cache is running low, then anonymous
      pages are force-scanned.
      
      This (total mess of a) behaviour is implicit and not obvious from the
      way the code is organized.  At least make it apparent in the code flow
      and document the conditions.  It will be it easier to come up with sane
      semantics later.
      Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NRik van Riel <riel@redhat.com>
      Reviewed-by: NSatoru Moriya <satoru.moriya@hds.com>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      10316b31
    • J
      mm: vmscan: save work scanning (almost) empty LRU lists · d778df51
      Johannes Weiner 提交于
      In certain cases (kswapd reclaim, memcg target reclaim), a fixed minimum
      amount of pages is scanned from the LRU lists on each iteration, to make
      progress.
      
      Do not make this minimum bigger than the respective LRU list size,
      however, and save some busy work trying to isolate and reclaim pages
      that are not there.
      
      Empty LRU lists are quite common with memory cgroups in NUMA
      environments because there exists a set of LRU lists for each zone for
      each memory cgroup, while the memory of a single cgroup is expected to
      stay on just one node.  The number of expected empty LRU lists is thus
      
        memcgs * (nodes - 1) * lru types
      
      Each attempt to reclaim from an empty LRU list does expensive size
      comparisons between lists, acquires the zone's lru lock etc.  Avoid
      that.
      Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: NRik van Riel <riel@redhat.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Satoru Moriya <satoru.moriya@hds.com>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d778df51
    • J
      mm: memcg: only evict file pages when we have plenty · 7c5bd705
      Johannes Weiner 提交于
      Commit e9868505 ("mm, vmscan: only evict file pages when we have
      plenty") makes a point of not going for anonymous memory while there is
      still enough inactive cache around.
      
      The check was added only for global reclaim, but it is just as useful to
      reduce swapping in memory cgroup reclaim:
      
          200M-memcg-defconfig-j2
      
                                           vanilla                   patched
          Real time              454.06 (  +0.00%)         453.71 (  -0.08%)
          User time              668.57 (  +0.00%)         668.73 (  +0.02%)
          System time            128.92 (  +0.00%)         129.53 (  +0.46%)
          Swap in               1246.80 (  +0.00%)         814.40 ( -34.65%)
          Swap out              1198.90 (  +0.00%)         827.00 ( -30.99%)
          Pages allocated   16431288.10 (  +0.00%)    16434035.30 (  +0.02%)
          Major faults           681.50 (  +0.00%)         593.70 ( -12.86%)
          THP faults             237.20 (  +0.00%)         242.40 (  +2.18%)
          THP collapse           241.20 (  +0.00%)         248.50 (  +3.01%)
          THP splits             157.30 (  +0.00%)         161.40 (  +2.59%)
      Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NRik van Riel <riel@redhat.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Satoru Moriya <satoru.moriya@hds.com>
      Cc: Simon Jeons <simon.jeons@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      7c5bd705