shrink_page_list() sets up a pagevec to release pages as according as they
are free.  It uses significant amounts of stack on the pagevec.  This
patch adds pages to be freed via pagevec to a linked list which is then
freed en-masse at the end.  This avoids using stack in the main path that
potentially calls writepage().
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NRik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

shrink_inactive_list() sets up a pagevec to release unfreeable pages.  It
uses significant amounts of stack doing this.  This patch splits
shrink_inactive_list() to take the stack usage out of the main path so
that callers to writepage() do not contain an unused pagevec on the stack.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NRik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove temporary variable that is only used once and does not help clarify
code.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NRik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now, max_scan of shrink_inactive_list() is always passed less than
SWAP_CLUSTER_MAX.  then, we can remove scanning pages loop in it.  This
patch also help stack diet.

detail
 - remove "while (nr_scanned < max_scan)" loop
 - remove nr_freed (now, we use nr_reclaimed directly)
 - remove nr_scan (now, we use nr_scanned directly)
 - rename max_scan to nr_to_scan
 - pass nr_to_scan into isolate_pages() directly instead
   using SWAP_CLUSTER_MAX

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: NRik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since 2.6.28 zone->prev_priority is unused. Then it can be removed
safely. It reduce stack usage slightly.

Now I have to say that I'm sorry. 2 years ago, I thought prev_priority
can be integrate again, it's useful. but four (or more) times trying
haven't got good performance number. Thus I give up such approach.

The rest of this changelog is notes on prev_priority and why it existed in
the first place and why it might be not necessary any more. This information
is based heavily on discussions between Andrew Morton, Rik van Riel and
Kosaki Motohiro who is heavily quotes from.

Historically prev_priority was important because it determined when the VM
would start unmapping PTE pages. i.e. there are no balances of note within
the VM, Anon vs File and Mapped vs Unmapped. Without prev_priority, there
is a potential risk of unnecessarily increasing minor faults as a large
amount of read activity of use-once pages could push mapped pages to the
end of the LRU and get unmapped.

There is no proof this is still a problem but currently it is not considered
to be. Active files are not deactivated if the active file list is smaller
than the inactive list reducing the liklihood that file-mapped pages are
being pushed off the LRU and referenced executable pages are kept on the
active list to avoid them getting pushed out by read activity.

Even if it is a problem, prev_priority prev_priority wouldn't works
nowadays. First of all, current vmscan still a lot of UP centric code. it
expose some weakness on some dozens CPUs machine. I think we need more and
more improvement.

The problem is, current vmscan mix up per-system-pressure, per-zone-pressure
and per-task-pressure a bit. example, prev_priority try to boost priority to
other concurrent priority. but if the another task have mempolicy restriction,
it is unnecessary, but also makes wrong big latency and exceeding reclaim.
per-task based priority + prev_priority adjustment make the emulation of
per-system pressure. but it have two issue 1) too rough and brutal emulation
2) we need per-zone pressure, not per-system.

Another example, currently DEF_PRIORITY is 12. it mean the lru rotate about
2 cycle (1/4096 + 1/2048 + 1/1024 + .. + 1) before invoking OOM-Killer.
but if 10,0000 thrreads enter DEF_PRIORITY reclaim at the same time, the
system have higher memory pressure than priority==0 (1/4096*10,000 > 2).
prev_priority can't solve such multithreads workload issue. In other word,
prev_priority concept assume the sysmtem don't have lots threads."
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: NRik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add a simple post-processing script for the reclaim-related trace events.
It can be used to give an indication of how much traffic there is on the
LRU lists and how severe latencies due to reclaim are.  Example output
looks like the following

Reclaim latencies expressed as order-latency_in_ms
uname-3942             9-200.179000000004 9-98.7900000000373 9-99.8330000001006
kswapd0-311            0-662.097999999998 0-2.79700000002049 \
	0-149.100000000035 0-3295.73600000003 0-9806.31799999997 0-35528.833 \
	0-10043.197 0-129740.979 0-3.50500000000466 0-3.54899999999907 \
	0-9297.78999999992 0-3.48499999998603 0-3596.97999999998 0-3.92799999995623 \
	0-3.35000000009313 0-16729.017 0-3.57799999997951 0-47435.0630000001 \
	0-3.7819999998901 0-5864.06999999995 0-18635.334 0-10541.289 9-186011.565 \
	9-3680.86300000001 9-1379.06499999994 9-958571.115 9-66215.474 \
	9-6721.14699999988 9-1962.15299999993 9-1094806.125 9-2267.83199999994 \
	9-47120.9029999999 9-427653.886 9-2.6359999999404 9-632.148999999976 \
	9-476.753000000026 9-495.577000000048 9-8.45900000003166 9-6.6820000000298 \
	9-1.30500000016764 9-251.746000000043 9-383.905000000028 9-80.1419999999925 \
	9-281.160000000149 9-14.8780000000261 9-381.45299999998 9-512.07799999998 \
	9-49.5519999999087 9-167.439000000013 9-183.820999999996 9-239.527999999933 \
	9-19.9479999998584 9-148.747999999905 9-164.583000000101 9-16.9480000000913 \
	9-192.376000000164 9-64.1010000000242 9-1.40800000005402 9-3.60800000000745 \
	9-17.1359999999404 9-4.69500000006519 9-2.06400000001304 9-1582488.554 \
	9-6244.19499999983 9-348153.812 9-2.0999999998603 9-0.987999999895692 \
	0-32218.473 0-1.6140000000596 0-1.28100000019185 0-1.41300000017509 \
	0-1.32299999985844 0-602.584000000032 0-1.34400000004098 0-1.6929999999702 \
	1-22101.8190000001 9-174876.724 9-16.2420000000857 9-175.165999999736 \
	9-15.8589999997057 9-0.604999999981374 9-3061.09000000032 9-479.277000000235 \
	9-1.54499999992549 9-771.985000000335 9-4.88700000010431 9-15.0649999999441 \
	9-0.879999999888241 9-252.01500000013 9-1381.03600000031 9-545.689999999944 \
	9-3438.0129999998 9-3343.70099999988
bench-stresshig-3942   9-7063.33900000004 9-129960.482 9-2062.27500000002 \
	9-3845.59399999992 9-171.82799999998 9-16493.821 9-7615.23900000006 \
	9-10217.848 9-983.138000000035 9-2698.39999999991 9-4016.1540000001 \
	9-5522.37700000009 9-21630.429 \
	9-15061.048 9-10327.953 9-542.69700000016 9-317.652000000002 \
	9-8554.71699999995 9-1786.61599999992 9-1899.31499999994 9-2093.41899999999 \
	9-4992.62400000007 9-942.648999999976 9-1923.98300000001 9-3.7980000001844 \
	9-5.99899999983609 9-0.912000000011176 9-1603.67700000014 9-1.98300000000745 \
	9-3.96500000008382 9-0.902999999932945 9-2802.72199999983 9-1078.24799999991 \
	9-2155.82900000014 9-10.058999999892 9-1984.723 9-1687.97999999998 \
	9-1136.05300000007 9-3183.61699999985 9-458.731000000145 9-6.48600000003353 \
	9-1013.25200000009 9-8415.22799999989 9-10065.584 9-2076.79600000009 \
	9-3792.65699999989 9-71.2010000001173 9-2560.96999999997 9-2260.68400000012 \
	9-2862.65799999982 9-1255.81500000018 9-15.7440000001807 9-4.33499999996275 \
	9-1446.63800000004 9-238.635000000009 9-60.1790000000037 9-4.38800000003539 \
	9-639.567000000039 9-306.698000000091 9-31.4070000001229 9-74.997999999905 \
	9-632.725999999791 9-1625.93200000003 9-931.266000000061 9-98.7749999999069 \
	9-984.606999999844 9-225.638999999966 9-421.316000000108 9-653.744999999879 \
	9-572.804000000004 9-769.158999999985 9-603.918000000063 9-4.28499999991618 \
	9-626.21399999992 9-1721.25 9-0.854999999981374 9-572.39599999995 \
	9-681.881999999983 9-1345.12599999993 9-363.666999999899 9-3823.31099999999 \
	9-2991.28200000012 9-4.27099999994971 9-309.76500000013 9-3068.35700000008 \
	9-788.25 9-3515.73999999999 9-2065.96100000013 9-286.719999999972 \
	9-316.076000000117 9-344.151000000071 9-2.51000000000931 9-306.688000000082 \
	9-1515.00099999993 9-336.528999999864 9-793.491999999853 9-457.348999999929 \
	9-13620.155 9-119.933999999892 9-35.0670000000391 9-918.266999999993 \
	9-828.569000000134 9-4863.81099999999 9-105.222000000067 9-894.23900000006 \
	9-110.964999999851 9-0.662999999942258 9-12753.3150000002 9-12.6129999998957 \
	9-13368.0899999999 9-12.4199999999255 9-1.00300000002608 9-1.41100000008009 \
	9-10300.5290000001 9-16.502000000095 9-30.7949999999255 9-6283.0140000002 \
	9-4320.53799999994 9-6826.27300000004 9-3.07299999985844 9-1497.26799999992 \
	9-13.4040000000969 9-3.12999999988824 9-3.86100000003353 9-11.3539999998175 \
	9-0.10799999977462 9-21.780999999959 9-209.695999999996 9-299.647000000114 \
	9-6.01699999999255 9-20.8349999999627 9-22.5470000000205 9-5470.16800000006 \
	9-7.60499999998137 9-0.821000000229105 9-1.56600000010803 9-14.1669999998994 \
	9-0.209000000031665 9-1.82300000009127 9-1.70000000018626 9-19.9429999999702 \
	9-124.266999999993 9-0.0389999998733401 9-6.71400000015274 9-16.7710000001825 \
	9-31.0409999999683 9-0.516999999992549 9-115.888000000035 9-5.19900000002235 \
	9-222.389999999898 9-11.2739999999758 9-80.9050000000279 9-8.14500000001863 \
	9-4.44599999999627 9-0.218999999808148 9-0.715000000083819 9-0.233000000007451
\
	9-48.2630000000354 9-248.560999999987 9-374.96800000011 9-644.179000000004 \
	9-0.835999999893829 9-79.0060000000522 9-128.447999999858 9-0.692000000039116 \
	9-5.26500000013039 9-128.449000000022 9-2.04799999995157 9-12.0990000001621 \
	9-8.39899999997579 9-10.3860000001732 9-11.9310000000987 9-53.4450000000652 \
	9-0.46999999997206 9-2.96299999998882 9-17.9699999999721 9-0.776000000070781 \
	9-25.2919999998994 9-33.1110000000335 9-0.434000000124797 9-0.641000000061467 \
	9-0.505000000121072 9-1.12800000002608 9-149.222000000067 9-1.17599999997765 \
	9-3247.33100000001 9-10.7439999999478 9-153.523000000045 9-1.38300000014715 \
	9-794.762000000104 9-3.36199999996461 9-128.765999999829 9-181.543999999994 \
	9-78149.8229999999 9-176.496999999974 9-89.9940000001807 9-9.12700000009499 \
	9-250.827000000048 9-0.224999999860302 9-0.388999999966472 9-1.16700000036508 \
	9-32.1740000001155 9-12.6800000001676 9-0.0720000001601875 9-0.274999999906868
\
	9-0.724000000394881 9-266.866000000387 9-45.5709999999963 9-4.54399999976158 \
	9-8.27199999988079 9-4.38099999958649 9-0.512000000104308 9-0.0640000002458692
\
	9-5.20000000018626 9-0.0839999997988343 9-12.816000000108 9-0.503000000026077 \
	9-0.507999999914318 9-6.23999999975786 9-3.35100000025705 9-18.8530000001192 \
	9-25.2220000000671 9-68.2309999996796 9-98.9939999999478 9-0.441000000108033 \
	9-4.24599999981001 9-261.702000000048 9-3.01599999982864 9-0.0749999997206032 \
	9-0.0370000000111759 9-4.375 9-3.21800000034273 9-11.3960000001825 \
	9-0.0540000000037253 9-0.286000000312924 9-0.865999999921769 \
	9-0.294999999925494 9-6.45999999996275 9-4.31099999975413 9-128.248999999836 \
	9-0.282999999821186 9-102.155000000261 9-0.0860000001266599 \
	9-0.0540000000037253 9-0.935000000055879 9-0.0670000002719462 \
	9-5.8640000000596 9-19.9860000000335 9-4.18699999991804 9-0.566000000108033 \
	9-2.55099999997765 9-0.702000000048429 9-131.653999999631 9-0.638999999966472 \
	9-14.3229999998584 9-183.398000000045 9-178.095999999903 9-3.22899999981746 \
	9-7.31399999978021 9-22.2400000002235 9-11.7979999999516 9-108.10599999968 \
	9-99.0159999998286 9-102.640999999829 9-38.414000000339
Process                  Direct     Wokeup      Pages      Pages    Pages
details                   Rclms     Kswapd    Scanned    Sync-IO ASync-IO
cc1-30800                     0          1          0          0        0      wakeup-0=1
cc1-24260                     0          1          0          0        0      wakeup-0=1
cc1-24152                     0         12          0          0        0      wakeup-0=12
cc1-8139                      0          1          0          0        0      wakeup-0=1
cc1-4390                      0          1          0          0        0      wakeup-0=1
cc1-4648                      0          7          0          0        0      wakeup-0=7
cc1-4552                      0          3          0          0        0      wakeup-0=3
dd-4550                       0         31          0          0        0      wakeup-0=31
date-4898                     0          1          0          0        0      wakeup-0=1
cc1-6549                      0          7          0          0        0      wakeup-0=7
as-22202                      0         17          0          0        0      wakeup-0=17
cc1-6495                      0          9          0          0        0      wakeup-0=9
cc1-8299                      0          1          0          0        0      wakeup-0=1
cc1-6009                      0          1          0          0        0      wakeup-0=1
cc1-2574                      0          2          0          0        0      wakeup-0=2
cc1-30568                     0          1          0          0        0      wakeup-0=1
cc1-2679                      0          6          0          0        0      wakeup-0=6
sh-13747                      0         12          0          0        0      wakeup-0=12
cc1-22193                     0         18          0          0        0      wakeup-0=18
cc1-30725                     0          2          0          0        0      wakeup-0=2
as-4392                       0          2          0          0        0      wakeup-0=2
cc1-28180                     0         14          0          0        0      wakeup-0=14
cc1-13697                     0          2          0          0        0      wakeup-0=2
cc1-22207                     0          8          0          0        0      wakeup-0=8
cc1-15270                     0        179          0          0        0      wakeup-0=179
cc1-22011                     0         82          0          0        0      wakeup-0=82
cp-14682                      0          1          0          0        0      wakeup-0=1
as-11926                      0          2          0          0        0      wakeup-0=2
cc1-6016                      0          5          0          0        0      wakeup-0=5
make-18554                    0         13          0          0        0      wakeup-0=13
cc1-8292                      0         12          0          0        0      wakeup-0=12
make-24381                    0          1          0          0        0      wakeup-1=1
date-18681                    0         33          0          0        0      wakeup-0=33
cc1-32276                     0          1          0          0        0      wakeup-0=1
timestamp-outpu-2809          0        253          0          0        0      wakeup-0=240 wakeup-1=13
date-18624                    0          7          0          0        0      wakeup-0=7
cc1-30960                     0          9          0          0        0      wakeup-0=9
cc1-4014                      0          1          0          0        0      wakeup-0=1
cc1-30706                     0         22          0          0        0      wakeup-0=22
uname-3942                    4          1        306          0       17      direct-9=4       wakeup-9=1
cc1-28207                     0          1          0          0        0      wakeup-0=1
cc1-30563                     0          9          0          0        0      wakeup-0=9
cc1-22214                     0         10          0          0        0      wakeup-0=10
cc1-28221                     0         11          0          0        0      wakeup-0=11
cc1-28123                     0          6          0          0        0      wakeup-0=6
kswapd0-311                   0          7     357302          0    34233      wakeup-0=7
cc1-5988                      0          7          0          0        0      wakeup-0=7
as-30734                      0        161          0          0        0      wakeup-0=161
cc1-22004                     0         45          0          0        0      wakeup-0=45
date-4590                     0          4          0          0        0      wakeup-0=4
cc1-15279                     0        213          0          0        0      wakeup-0=213
date-30735                    0          1          0          0        0      wakeup-0=1
cc1-30583                     0          4          0          0        0      wakeup-0=4
cc1-32324                     0          2          0          0        0      wakeup-0=2
cc1-23933                     0          3          0          0        0      wakeup-0=3
cc1-22001                     0         36          0          0        0      wakeup-0=36
bench-stresshig-3942        287        287      80186       6295    12196      direct-9=287       wakeup-9=287
cc1-28170                     0          7          0          0        0      wakeup-0=7
date-7932                     0         92          0          0        0      wakeup-0=92
cc1-22222                     0          6          0          0        0      wakeup-0=6
cc1-32334                     0         16          0          0        0      wakeup-0=16
cc1-2690                      0          6          0          0        0      wakeup-0=6
cc1-30733                     0          9          0          0        0      wakeup-0=9
cc1-32298                     0          2          0          0        0      wakeup-0=2
cc1-13743                     0         18          0          0        0      wakeup-0=18
cc1-22186                     0          4          0          0        0      wakeup-0=4
cc1-28214                     0         11          0          0        0      wakeup-0=11
cc1-13735                     0          1          0          0        0      wakeup-0=1
updatedb-8173                 0         18          0          0        0      wakeup-0=18
cc1-13750                     0          3          0          0        0      wakeup-0=3
cat-2808                      0          2          0          0        0      wakeup-0=2
cc1-15277                     0        169          0          0        0      wakeup-0=169
date-18317                    0          1          0          0        0      wakeup-0=1
cc1-15274                     0        197          0          0        0      wakeup-0=197
cc1-30732                     0          1          0          0        0      wakeup-0=1

Kswapd                   Kswapd      Order      Pages      Pages    Pages
Instance                Wakeups  Re-wakeup    Scanned    Sync-IO ASync-IO
kswapd0-311                  91         24     357302          0    34233      wake-0=31 wake-1=1 wake-9=59       rewake-0=10 rewake-1=1 rewake-9=13

Summary
Direct reclaims:     		291
Direct reclaim pages scanned:	437794
Direct reclaim write sync I/O:	6295
Direct reclaim write async I/O:	46446
Wake kswapd requests:		2152
Time stalled direct reclaim: 	519.163009000002 ms

Kswapd wakeups:			91
Kswapd pages scanned:		357302
Kswapd reclaim write sync I/O:	0
Kswapd reclaim write async I/O:	34233
Time kswapd awake:		5282.749757 ms
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NLarry Woodman <lwoodman@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add a trace event for when page reclaim queues a page for IO and records
whether it is synchronous or asynchronous.  Excessive synchronous IO for a
process can result in noticeable stalls during direct reclaim.  Excessive
IO from page reclaim may indicate that the system is seriously under
provisioned for the amount of dirty pages that exist.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NLarry Woodman <lwoodman@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add an event for when pages are isolated en-masse from the LRU lists.
This event augments the information available on LRU traffic and can be
used to evaluate lumpy reclaim.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NLarry Woodman <lwoodman@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add two trace events for kswapd waking up and going asleep for the
purposes of tracking kswapd activity and two trace events for direct
reclaim beginning and ending.  The information can be used to work out how
much time a process or the system is spending on the reclamation of pages
and in the case of direct reclaim, how many pages were reclaimed for that
process.  High frequency triggering of these events could point to memory
pressure problems.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NLarry Woodman <lwoodman@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

shrink_zones() need relatively long time and lru_pages can change
dramatically during shrink_zones().  So lru_pages should be recalculated
for each priority.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: NRik van Riel <riel@redhat.com>
Reviewed-by: NMinchan Kim <minchan.kim@gmail.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Swap token don't works when zone reclaim is enabled since it was born.
Because __zone_reclaim() always call disable_swap_token() unconditionally.

This kill swap token feature completely.  As far as I know, nobody want to
that.  Remove it.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: NRik van Riel <riel@redhat.com>
Reviewed-by: NMinchan Kim <minchan.kim@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We try to avoid livelocks of writeback when some steadily creates dirty
pages in a mapping we are writing out.  For memory-cleaning writeback,
using nr_to_write works reasonably well but we cannot really use it for
data integrity writeback.  This patch tries to solve the problem.

The idea is simple: Tag all pages that should be written back with a
special tag (TOWRITE) in the radix tree.  This can be done rather quickly
and thus livelocks should not happen in practice.  Then we start doing the
hard work of locking pages and sending them to disk only for those pages
that have TOWRITE tag set.

Note: Adding new radix tree tag grows radix tree node from 288 to 296
bytes for 32-bit archs and from 552 to 560 bytes for 64-bit archs.
However, the number of slab/slub items per page remains the same (13 and 7
respectively).
Signed-off-by: NJan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Implement function for setting one tag if another tag is set for each item
in given range.
Signed-off-by: NJan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Verify the refcounting doesn't go wrong, and resurrect the check in
__page_check_anon_rmap as in old anon-vma code.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Signed-off-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>

With root anon-vma it's trivial to keep doing the usual check as in
old-anon-vma code.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Signed-off-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>

Always use anon_vma->root pointer instead of anon_vma_chain.prev.

Also optimize the map-paths, if a mapping is already established no need
to overwrite it with root anon-vma list, we can keep the more finegrined
anon-vma and skip the overwrite: see the PageAnon check in !exclusive
case.  This is also the optimization that hidden the ksm bug as this tends
to make ksm_might_need_to_copy skip the copy, but only the proper fix to
ksm_might_need_to_copy guarantees not triggering the ksm bug unless ksm is
in use.  this is an optimization only...

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Signed-off-by: NRik van Riel <riel@redhat.com>
[kamezawa.hiroyu@jp.fujitsu.com: fix false positive BUG_ON in __page_set_anon_rmap]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The new anon-vma code, was suboptimal and it lead to erratic invocation of
ksm_does_need_to_copy.  That leads to host hangs or guest vnc lockup, or
weird behavior.  It's unclear why ksm_does_need_to_copy is unstable but
the point is that when KSM is not in use, ksm_does_need_to_copy must never
run or we bounce pages for no good reason.  I suspect the same hangs will
happen with KVM swaps.  But this at least fixes the regression in the
new-anon-vma code and it only let KSM bugs triggers when KSM is in use.

The code in do_swap_page likely doesn't cope well with a not-swapcache,
especially the memcg code.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Signed-off-by: NRik van Riel <riel@redhat.com>
Cc: Izik Eidus <ieidus@yahoo.com>
Cc: Avi Kivity <avi@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make sure to always add new VMAs at the end of the list.  This is
important so rmap_walk does not miss a VMA that was created during the
rmap_walk.

The old code got this right most of the time due to luck, but was buggy
when anon_vma_prepare reused a mergeable anon_vma.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Signed-off-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>

There's no anon-vma related mangling happening inside __vma_link anymore
so no need of anon_vma locking there.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Signed-off-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>

I'm running a shmem pagefault test case (see attached file) under a 64 CPU
system.  Profile shows shmem_inode_info->lock is heavily contented and
100% CPUs time are trying to get the lock.  In the pagefault (no swap)
case, shmem_getpage gets the lock twice, the last one is avoidable if we
prealloc a page so we could reduce one time of locking.  This is what
below patch does.

The result of the test case:
2.6.35-rc3: ~20s
2.6.35-rc3 + patch: ~12s
so this is 40% improvement.

One might argue if we could have better locking for shmem.  But even shmem
is lockless, the pagefault will soon have pagecache lock heavily contented
because shmem must add new page to pagecache.  So before we have better
locking for pagecache, improving shmem locking doesn't have too much
improvement.  I did a similar pagefault test against a ramfs file, the
test result is ~10.5s.

[akpm@linux-foundation.org: fix comment, clean up code layout, elimintate code duplication]
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Zhang, Yanmin" <yanmin.zhang@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The current implementation of tmpfs is not scalable.  We found that
stat_lock is contended by multiple threads when we need to get a new page,
leading to useless spinning inside this spin lock.

This patch makes use of the percpu_counter library to maintain local count
of used blocks to speed up getting and returning of pages.  So the
acquisition of stat_lock is unnecessary for getting and returning blocks,
improving the performance of tmpfs on system with large number of cpus.
On a 4 socket 32 core NHM-EX system, we saw improvement of 270%.

The implementation below has a slight chance of race between threads
causing a slight overshoot of the maximum configured blocks.  However, any
overshoot is small, and is bounded by the number of cpus.  This happens
when the number of used blocks is slightly below the maximum configured
blocks when a thread checks the used block count, and another thread
allocates the last block before the current thread does.  This should not
be a problem for tmpfs, as the overshoot is most likely to be a few blocks
and bounded.  If a strict limit is really desired, then configured the max
blocks to be the limit less the number of cpus in system.
Signed-off-by: NTim Chen <tim.c.chen@linux.intel.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>

Add percpu_counter_compare that allows for a quick but accurate comparison
of percpu_counter with a given value.

A rough count is provided by the count field in percpu_counter structure,
without accounting for the other values stored in individual cpu counters.

The actual count is a sum of count and the cpu counters.  However, count
field is never different from the actual value by a factor of
batch*num_online_cpu.  We do not need to get actual count for comparison
if count is different from the given value by this factor and allows for
quick comparison without summing up all the per cpu counters.
Signed-off-by: NTim Chen <tim.c.chen@linux.intel.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>

No real bugs, just some dead code and some fixups.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Avoid quite a lot of warnings in header files in a gcc 4.6 -Wall builds
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As explained in commit 1c0fe6e3 ("mm: invoke oom-killer from page
fault") , we want to call the architecture independent oom killer when
getting an unexplained OOM from handle_mm_fault, rather than simply
killing current.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Acked-by: NHaavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

migrate_pages() is using >500 bytes stack. Reduce it.

   mm/mempolicy.c: In function 'sys_migrate_pages':
   mm/mempolicy.c:1344: warning: the frame size of 528 bytes is larger than 512 bytes

[akpm@linux-foundation.org: don't play with a might-be-NULL pointer]
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: NChristoph Lameter <cl@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Define stubs for the numa_*_id() generic percpu related functions for
non-NUMA configurations in <asm-generic/topology.h> where the other
non-numa stubs live.

Fixes ia64 !NUMA build breakage -- e.g., tiger_defconfig

Back out now unneeded '#ifndef CONFIG_NUMA' guards from ia64 smpboot.c
Signed-off-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Tested-by: NTony Luck <tony.luck@intel.com>
Acked-by: NTony Luck <tony.luck@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

get_zone_counts() was dropped from kernel tree, see:
http://www.mail-archive.com/mm-commits@vger.kernel.org/msg07313.html but
its prototype remains.
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The sum_vm_events passes cpumask for for_each_cpu().  But it's useless
since we have for_each_online_cpu.  Althougth it's tirival overhead, it's
not good about coding consistency.

Let's use for_each_online_cpu instead of for_each_cpu with cpumask
argument.
Signed-off-by: NMinchan Kim <minchan.kim@gmail.com>
Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NChristoph Lameter <cl@linux-foundation.org>
Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

__out_of_memory() only has a single caller, so fold it into
out_of_memory() and add a comment about locking for its call to
oom_kill_process().
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

select_bad_process() and __out_of_memory() doe not need their enum
oom_constraint arguments: it's possible to pass a NULL nodemask if
constraint == CONSTRAINT_MEMORY_POLICY in the caller, out_of_memory().
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We have been used naming try_set_zone_oom and clear_zonelist_oom.
The role of functions is to lock of zonelist for preventing parallel
OOM. So clear_zonelist_oom makes sense but try_set_zone_oome is rather
awkward and unmatched with clear_zonelist_oom.

Let's change it with try_set_zonelist_oom.
Signed-off-by: NMinchan Kim <minchan.kim@gmail.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.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>

Remove the redundancy in __oom_kill_task() since:

 - init can never be passed to this function: it will never be PF_EXITING
   or selectable from select_bad_process(), and

 - it will never be passed a task from oom_kill_task() without an ->mm
   and we're unconcerned about detachment from exiting tasks, there's no
   reason to protect them against SIGKILL or access to memory reserves.

Also moves the kernel log message to a higher level since the verbosity is
not always emitted here; we need not print an error message if an exiting
task is given a longer timeslice.

__oom_kill_task() only has a single caller, so it can be merged into that
function at the same time.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.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>

The three oom killer sysctl variables (sysctl_oom_dump_tasks,
sysctl_oom_kill_allocating_task, and sysctl_panic_on_oom) are better
declared in include/linux/oom.h rather than kernel/sysctl.c.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.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>

It is possible to remove the special pagefault oom handler by simply oom
locking all system zones and then calling directly into out_of_memory().

All populated zones must have ZONE_OOM_LOCKED set, otherwise there is a
parallel oom killing in progress that will lead to eventual memory freeing
so it's not necessary to needlessly kill another task.  The context in
which the pagefault is allocating memory is unknown to the oom killer, so
this is done on a system-wide level.

If a task has already been oom killed and hasn't fully exited yet, this
will be a no-op since select_bad_process() recognizes tasks across the
system with TIF_MEMDIE set.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NNick Piggin <npiggin@suse.de>
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.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>

There are various points in the oom killer where the kernel must determine
whether to panic or not.  It's better to extract this to a helper function
to remove all the confusion as to its semantics.

Also fix a call to dump_header() where tasklist_lock is not read- locked,
as required.

There's no functional change with this patch.
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NDavid Rientjes <rientjes@google.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>

If memory has been depleted in lowmem zones even with the protection
afforded to it by /proc/sys/vm/lowmem_reserve_ratio, it is unlikely that
killing current users will help.  The memory is either reclaimable (or
migratable) already, in which case we should not invoke the oom killer at
all, or it is pinned by an application for I/O.  Killing such an
application may leave the hardware in an unspecified state and there is no
guarantee that it will be able to make a timely exit.

Lowmem allocations are now failed in oom conditions when __GFP_NOFAIL is
not used so that the task can perhaps recover or try again later.

Previously, the heuristic provided some protection for those tasks with
CAP_SYS_RAWIO, but this is no longer necessary since we will not be
killing tasks for the purposes of ISA allocations.

high_zoneidx is gfp_zone(gfp_flags), meaning that ZONE_NORMAL will be the
default for all allocations that are not __GFP_DMA, __GFP_DMA32,
__GFP_HIGHMEM, and __GFP_MOVABLE on kernels configured to support those
flags.  Testing for high_zoneidx being less than ZONE_NORMAL will only
return true for allocations that have either __GFP_DMA or __GFP_DMA32.
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NDavid Rientjes <rientjes@google.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>

The oom killer tasklist dump, enabled with the oom_dump_tasks sysctl, is
very helpful information in diagnosing why a user's task has been killed.
It emits useful information such as each eligible thread's memory usage
that can determine why the system is oom, so it should be enabled by
default.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.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>

The oom killer presently kills current whenever there is no more memory
free or reclaimable on its mempolicy's nodes.  There is no guarantee that
current is a memory-hogging task or that killing it will free any
substantial amount of memory, however.

In such situations, it is better to scan the tasklist for nodes that are
allowed to allocate on current's set of nodes and kill the task with the
highest badness() score.  This ensures that the most memory-hogging task,
or the one configured by the user with /proc/pid/oom_adj, is always
selected in such scenarios.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.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>

When a task is chosen for oom kill, the oom killer first attempts to
sacrifice a child not sharing its parent's memory instead.  Unfortunately,
this often kills in a seemingly random fashion based on the ordering of
the selected task's child list.  Additionally, it is not guaranteed at all
to free a large amount of memory that we need to prevent additional oom
killing in the very near future.

Instead, we now only attempt to sacrifice the worst child not sharing its
parent's memory, if one exists.  The worst child is indicated with the
highest badness() score.  This serves two advantages: we kill a
memory-hogging task more often, and we allow the configurable
/proc/pid/oom_adj value to be considered as a factor in which child to
kill.

Reviewers may observe that the previous implementation would iterate
through the children and attempt to kill each until one was successful and
then the parent if none were found while the new code simply kills the
most memory-hogging task or the parent.  Note that the only time
oom_kill_task() fails, however, is when a child does not have an mm or has
a /proc/pid/oom_adj of OOM_DISABLE.  badness() returns 0 for both cases,
so the final oom_kill_task() will always succeed.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NNick Piggin <npiggin@suse.de>
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>