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			2 Commits
		
	
	
	| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
|  Mel Gorman | e11da5b4fd | tracing, vmscan: add trace events for LRU list shrinking There have been numerous reports of stalls that pointed at the problem
being somewhere in the VM.  There are multiple roots to the problems which
means dealing with any of the root problems in isolation is tricky to
justify on their own and they would still need integration testing.  This
patch series puts together two different patch sets which in combination
should tackle some of the root causes of latency problems being reported.
Patch 1 adds a tracepoint for shrink_inactive_list.  For this series, the
most important results is being able to calculate the scanning/reclaim
ratio as a measure of the amount of work being done by page reclaim.
Patch 2 accounts for time spent in congestion_wait.
Patches 3-6 were originally developed by Kosaki Motohiro but reworked for
this series.  It has been noted that lumpy reclaim is far too aggressive
and trashes the system somewhat.  As SLUB uses high-order allocations, a
large cost incurred by lumpy reclaim will be noticeable.  It was also
reported during transparent hugepage support testing that lumpy reclaim
was trashing the system and these patches should mitigate that problem
without disabling lumpy reclaim.
Patch 7 adds wait_iff_congested() and replaces some callers of
congestion_wait().  wait_iff_congested() only sleeps if there is a BDI
that is currently congested.  Patch 8 notes that any BDI being congested
is not necessarily a problem because there could be multiple BDIs of
varying speeds and numberous zones.  It attempts to track when a zone
being reclaimed contains many pages backed by a congested BDI and if so,
reclaimers wait on the congestion queue.
I ran a number of tests with monitoring on X86, X86-64 and PPC64. Each
machine had 3G of RAM and the CPUs were
X86:    Intel P4 2-core
X86-64: AMD Phenom 4-core
PPC64:  PPC970MP
Each used a single disk and the onboard IO controller.  Dirty ratio was
left at 20.  I'm just going to report for X86-64 and PPC64 in a vague
attempt to keep this report short.  Four kernels were tested each based on
v2.6.36-rc4
traceonly-v2r2:     Patches 1 and 2 to instrument vmscan reclaims and congestion_wait
lowlumpy-v2r3:      Patches 1-6 to test if lumpy reclaim is better
waitcongest-v2r3:   Patches 1-7 to only wait on congestion
waitwriteback-v2r4: Patches 1-8 to detect when a zone is congested
nocongest-v1r5: Patches 1-3 for testing wait_iff_congestion
nodirect-v1r5:  Patches 1-10 to disable filesystem writeback for better IO
The tests run were as follows
kernbench
	compile-based benchmark. Smoke test performance
sysbench
	OLTP read-only benchmark. Will be re-run in the future as read-write
micro-mapped-file-stream
	This is a micro-benchmark from Johannes Weiner that accesses a
	large sparse-file through mmap(). It was configured to run in only
	single-CPU mode but can be indicative of how well page reclaim
	identifies suitable pages.
stress-highalloc
	Tries to allocate huge pages under heavy load.
kernbench, iozone and sysbench did not report any performance regression
on any machine.  sysbench did pressure the system lightly and there was
reclaim activity but there were no difference of major interest between
the kernels.
X86-64 micro-mapped-file-stream
                                      traceonly-v2r2           lowlumpy-v2r3        waitcongest-v2r3     waitwriteback-v2r4
pgalloc_dma                       1639.00 (   0.00%)       667.00 (-145.73%)      1167.00 ( -40.45%)       578.00 (-183.56%)
pgalloc_dma32                  2842410.00 (   0.00%)   2842626.00 (   0.01%)   2843043.00 (   0.02%)   2843014.00 (   0.02%)
pgalloc_normal                       0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)
pgsteal_dma                        729.00 (   0.00%)        85.00 (-757.65%)       609.00 ( -19.70%)       125.00 (-483.20%)
pgsteal_dma32                  2338721.00 (   0.00%)   2447354.00 (   4.44%)   2429536.00 (   3.74%)   2436772.00 (   4.02%)
pgsteal_normal                       0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)
pgscan_kswapd_dma                 1469.00 (   0.00%)       532.00 (-176.13%)      1078.00 ( -36.27%)       220.00 (-567.73%)
pgscan_kswapd_dma32            4597713.00 (   0.00%)   4503597.00 (  -2.09%)   4295673.00 (  -7.03%)   3891686.00 ( -18.14%)
pgscan_kswapd_normal                 0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)
pgscan_direct_dma                   71.00 (   0.00%)       134.00 (  47.01%)       243.00 (  70.78%)       352.00 (  79.83%)
pgscan_direct_dma32             305820.00 (   0.00%)    280204.00 (  -9.14%)    600518.00 (  49.07%)    957485.00 (  68.06%)
pgscan_direct_normal                 0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)         0.00 (   0.00%)
pageoutrun                       16296.00 (   0.00%)     21254.00 (  23.33%)     18447.00 (  11.66%)     20067.00 (  18.79%)
allocstall                         443.00 (   0.00%)       273.00 ( -62.27%)       513.00 (  13.65%)      1568.00 (  71.75%)
These are based on the raw figures taken from /proc/vmstat.  It's a rough
measure of reclaim activity.  Note that allocstall counts are higher
because we are entering direct reclaim more often as a result of not
sleeping in congestion.  In itself, it's not necessarily a bad thing.
It's easier to get a view of what happened from the vmscan tracepoint
report.
FTrace Reclaim Statistics: vmscan
                                traceonly-v2r2   lowlumpy-v2r3 waitcongest-v2r3 waitwriteback-v2r4
Direct reclaims                                443        273        513       1568
Direct reclaim pages scanned                305968     280402     600825     957933
Direct reclaim pages reclaimed               43503      19005      30327     117191
Direct reclaim write file async I/O              0          0          0          0
Direct reclaim write anon async I/O              0          3          4         12
Direct reclaim write file sync I/O               0          0          0          0
Direct reclaim write anon sync I/O               0          0          0          0
Wake kswapd requests                        187649     132338     191695     267701
Kswapd wakeups                                   3          1          4          1
Kswapd pages scanned                       4599269    4454162    4296815    3891906
Kswapd pages reclaimed                      | ||
|  Mel Gorman | b898cc7001 | vmscan: tracing: add a postprocessing script for reclaim-related ftrace events 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: Mel Gorman <mel@csn.ul.ie> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Larry 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |