13 Jan, 2012
40 commits
-
Asynchronous compaction is used when allocating transparent hugepages to
avoid blocking for long periods of time. Due to reports of stalling,
there was a debate on disabling synchronous compaction but this severely
impacted allocation success rates. Part of the reason was that many dirty
pages are skipped in asynchronous compaction by the following check;if (PageDirty(page) && !sync &&
mapping->a_ops->migratepage != migrate_page)
rc = -EBUSY;This skips over all mapping aops using buffer_migrate_page() even though
it is possible to migrate some of these pages without blocking. This
patch updates the ->migratepage callback with a "sync" parameter. It is
the responsibility of the callback to fail gracefully if migration would
block.Signed-off-by: Mel Gorman
Reviewed-by: Rik van Riel
Cc: Andrea Arcangeli
Cc: Minchan Kim
Cc: Dave Jones
Cc: Jan Kara
Cc: Andy Isaacson
Cc: Nai Xia
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
During direct reclaim it is possible that reclaim will be aborted so that
compaction can be attempted to satisfy a high-order allocation. If this
decision is made before any pages are reclaimed, it is possible that 0 is
returned to the page allocator potentially triggering an OOM. This has
not been observed but it is a possibility so this patch addresses it.Signed-off-by: Mel Gorman
Reviewed-by: Rik van Riel
Cc: Andrea Arcangeli
Cc: Minchan Kim
Cc: Dave Jones
Cc: Jan Kara
Cc: Andy Isaacson
Cc: Nai Xia
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Properly take into account if we isolated a compound page during the lumpy
scan in reclaim and skip over the tail pages when encountered. This
corrects the values given to the tracepoint for number of lumpy pages
isolated and will avoid breaking the loop early if compound pages smaller
than the requested allocation size are requested.[mgorman@suse.de: Updated changelog]
Signed-off-by: Andrea Arcangeli
Signed-off-by: Mel Gorman
Reviewed-by: Minchan Kim
Reviewed-by: Rik van Riel
Cc: Dave Jones
Cc: Jan Kara
Cc: Andy Isaacson
Cc: Nai Xia
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When asynchronous compaction was introduced, the
/proc/sys/vm/compact_memory handler should have been updated to always use
synchronous compaction. This did not happen so this patch addresses it.The assumption is if a user writes to /proc/sys/vm/compact_memory, they
are willing for that process to stall.Signed-off-by: Mel Gorman
Reviewed-by: Andrea Arcangeli
Reviewed-by: Rik van Riel
Reviewed-by: Minchan Kim
Cc: Dave Jones
Cc: Jan Kara
Cc: Andy Isaacson
Cc: Nai Xia
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Short summary: There are severe stalls when a USB stick using VFAT is
used with THP enabled that are reduced by this series. If you are
experiencing this problem, please test and report back and considering I
have seen complaints from openSUSE and Fedora users on this as well as a
few private mails, I'm guessing it's a widespread issue. This is a new
type of USB-related stall because it is due to synchronous compaction
writing where as in the past the big problem was dirty pages reaching
the end of the LRU and being written by reclaim.Am cc'ing Andrew this time and this series would replace
mm-do-not-stall-in-synchronous-compaction-for-thp-allocations.patch.
I'm also cc'ing Dave Jones as he might have merged that patch to Fedora
for wider testing and ideally it would be reverted and replaced by this
series.That said, the later patches could really do with some review. If this
series is not the answer then a new direction needs to be discussed
because as it is, the stalls are unacceptable as the results in this
leader show.For testers that try backporting this to 3.1, it won't work because
there is a non-obvious dependency on not writing back pages in direct
reclaim so you need those patches too.Changelog since V5
o Rebase to 3.2-rc5
o Tidy up the changelogs a bitChangelog since V4
o Added reviewed-bys, credited Andrea properly for sync-light
o Allow dirty pages without mappings to be considered for migration
o Bound the number of pages freed for compaction
o Isolate PageReclaim pages on their own LRU listThis is against 3.2-rc5 and follows on from discussions on "mm: Do
not stall in synchronous compaction for THP allocations" and "[RFC
PATCH 0/5] Reduce compaction-related stalls". Initially, the proposed
patch eliminated stalls due to compaction which sometimes resulted in
user-visible interactivity problems on browsers by simply never using
sync compaction. The downside was that THP success allocation rates
were lower because dirty pages were not being migrated as reported by
Andrea. His approach at fixing this was nacked on the grounds that
it reverted fixes from Rik merged that reduced the amount of pages
reclaimed as it severely impacted his workloads performance.This series attempts to reconcile the requirements of maximising THP
usage, without stalling in a user-visible fashion due to compaction
or cheating by reclaiming an excessive number of pages.Patch 1 partially reverts commit 39deaf85 to allow migration to isolate
dirty pages. This is because migration can move some dirty
pages without blocking.Patch 2 notes that the /proc/sys/vm/compact_memory handler is not using
synchronous compaction when it should be. This is unrelated
to the reported stalls but is worth fixing.Patch 3 checks if we isolated a compound page during lumpy scan and
account for it properly. For the most part, this affects
tracing so it's unrelated to the stalls but worth fixing.Patch 4 notes that it is possible to abort reclaim early for compaction
and return 0 to the page allocator potentially entering the
"may oom" path. This has not been observed in practice but
the rest of the series potentially makes it easier to happen.Patch 5 adds a sync parameter to the migratepage callback and gives
the callback responsibility for migrating the page without
blocking if sync==false. For example, fallback_migrate_page
will not call writepage if sync==false. This increases the
number of pages that can be handled by asynchronous compaction
thereby reducing stalls.Patch 6 restores filter-awareness to isolate_lru_page for migration.
In practice, it means that pages under writeback and pages
without a ->migratepage callback will not be isolated
for migration.Patch 7 avoids calling direct reclaim if compaction is deferred but
makes sure that compaction is only deferred if sync
compaction was used.Patch 8 introduces a sync-light migration mechanism that sync compaction
uses. The objective is to allow some stalls but to not call
->writepage which can lead to significant user-visible stalls.Patch 9 notes that while we want to abort reclaim ASAP to allow
compation to go ahead that we leave a very small window of
opportunity for compaction to run. This patch allows more pages
to be freed by reclaim but bounds the number to a reasonable
level based on the high watermark on each zone.Patch 10 allows slabs to be shrunk even after compaction_ready() is
true for one zone. This is to avoid a problem whereby a single
small zone can abort reclaim even though no pages have been
reclaimed and no suitably large zone is in a usable state.Patch 11 fixes a problem with the rate of page scanning. As reclaim is
rarely stalling on pages under writeback it means that scan
rates are very high. This is particularly true for direct
reclaim which is not calling writepage. The vmstat figures
implied that much of this was busy work with PageReclaim pages
marked for immediate reclaim. This patch is a prototype that
moves these pages to their own LRU list.This has been tested and other than 2 USB keys getting trashed,
nothing horrible fell out. That said, I am a bit unhappy with the
rescue logic in patch 11 but did not find a better way around it. It
does significantly reduce scan rates and System CPU time indicating
it is the right direction to take.What is of critical importance is that stalls due to compaction
are massively reduced even though sync compaction was still
allowed. Testing from people complaining about stalls copying to USBs
with THP enabled are particularly welcome.The following tests all involve THP usage and USB keys in some
way. Each test follows this type of pattern1. Read from some fast fast storage, be it raw device or file. Each time
the copy finishes, start again until the test ends
2. Write a large file to a filesystem on a USB stick. Each time the copy
finishes, start again until the test ends
3. When memory is low, start an alloc process that creates a mapping
the size of physical memory to stress THP allocation. This is the
"real" part of the test and the part that is meant to trigger
stalls when THP is enabled. Copying continues in the background.
4. Record the CPU usage and time to execute of the alloc process
5. Record the number of THP allocs and fallbacks as well as the number of THP
pages in use a the end of the test just before alloc exited
6. Run the test 5 times to get an idea of variability
7. Between each run, sync is run and caches dropped and the test
waits until nr_dirty is a small number to avoid interference
or caching between iterations that would skew the figures.The individual tests were then
writebackCPDeviceBasevfat
Disable THP, read from a raw device (sda), vfat on USB stick
writebackCPDeviceBaseext4
Disable THP, read from a raw device (sda), ext4 on USB stick
writebackCPDevicevfat
THP enabled, read from a raw device (sda), vfat on USB stick
writebackCPDeviceext4
THP enabled, read from a raw device (sda), ext4 on USB stick
writebackCPFilevfat
THP enabled, read from a file on fast storage and USB, both vfat
writebackCPFileext4
THP enabled, read from a file on fast storage and USB, both ext4The kernels tested were
3.1 3.1
vanilla 3.2-rc5
freemore Patches 1-10
immediate Patches 1-11
andrea The 8 patches Andrea posted as a basis of comparisonThe results are very long unfortunately. I'll start with the case
where we are not using THP at allwritebackCPDeviceBasevfat
3.1.0-vanilla rc5-vanilla freemore-v6r1 isolate-v6r1 andrea-v2r1
System Time 1.28 ( 0.00%) 54.49 (-4143.46%) 48.63 (-3687.69%) 4.69 ( -265.11%) 51.88 (-3940.81%)
+/- 0.06 ( 0.00%) 2.45 (-4305.55%) 4.75 (-8430.57%) 7.46 (-13282.76%) 4.76 (-8440.70%)
User Time 0.09 ( 0.00%) 0.05 ( 40.91%) 0.06 ( 29.55%) 0.07 ( 15.91%) 0.06 ( 27.27%)
+/- 0.02 ( 0.00%) 0.01 ( 45.39%) 0.02 ( 25.07%) 0.00 ( 77.06%) 0.01 ( 52.24%)
Elapsed Time 110.27 ( 0.00%) 56.38 ( 48.87%) 49.95 ( 54.70%) 11.77 ( 89.33%) 53.43 ( 51.54%)
+/- 7.33 ( 0.00%) 3.77 ( 48.61%) 4.94 ( 32.63%) 6.71 ( 8.50%) 4.76 ( 35.03%)
THP Active 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%)
+/- 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%)
Fault Alloc 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%)
+/- 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%)
Fault Fallback 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%)
+/- 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%)The THP figures are obviously all 0 because THP was enabled. The
main thing to watch is the elapsed times and how they compare to
times when THP is enabled later. It's also important to note that
elapsed time is improved by this series as System CPu time is much
reduced.writebackCPDevicevfat
3.1.0-vanilla rc5-vanilla freemore-v6r1 isolate-v6r1 andrea-v2r1
System Time 1.22 ( 0.00%) 13.89 (-1040.72%) 46.40 (-3709.20%) 4.44 ( -264.37%) 47.37 (-3789.33%)
+/- 0.06 ( 0.00%) 22.82 (-37635.56%) 3.84 (-6249.44%) 6.48 (-10618.92%) 6.60
(-10818.53%)
User Time 0.06 ( 0.00%) 0.06 ( -6.90%) 0.05 ( 17.24%) 0.05 ( 13.79%) 0.04 ( 31.03%)
+/- 0.01 ( 0.00%) 0.01 ( 33.33%) 0.01 ( 33.33%) 0.01 ( 39.14%) 0.01 ( 25.46%)
Elapsed Time 10445.54 ( 0.00%) 2249.92 ( 78.46%) 70.06 ( 99.33%) 16.59 ( 99.84%) 472.43 (
95.48%)
+/- 643.98 ( 0.00%) 811.62 ( -26.03%) 10.02 ( 98.44%) 7.03 ( 98.91%) 59.99 ( 90.68%)
THP Active 15.60 ( 0.00%) 35.20 ( 225.64%) 65.00 ( 416.67%) 70.80 ( 453.85%) 62.20 ( 398.72%)
+/- 18.48 ( 0.00%) 51.29 ( 277.59%) 15.99 ( 86.52%) 37.91 ( 205.18%) 22.02 ( 119.18%)
Fault Alloc 121.80 ( 0.00%) 76.60 ( 62.89%) 155.40 ( 127.59%) 181.20 ( 148.77%) 286.60 ( 235.30%)
+/- 73.51 ( 0.00%) 61.11 ( 83.12%) 34.89 ( 47.46%) 31.88 ( 43.36%) 68.13 ( 92.68%)
Fault Fallback 881.20 ( 0.00%) 926.60 ( -5.15%) 847.60 ( 3.81%) 822.00 ( 6.72%) 716.60 ( 18.68%)
+/- 73.51 ( 0.00%) 61.26 ( 16.67%) 34.89 ( 52.54%) 31.65 ( 56.94%) 67.75 ( 7.84%)
MMTests Statistics: duration
User/Sys Time Running Test (seconds) 3540.88 1945.37 716.04 64.97 1937.03
Total Elapsed Time (seconds) 52417.33 11425.90 501.02 230.95 2520.28The first thing to note is the "Elapsed Time" for the vanilla kernels
of 2249 seconds versus 56 with THP disabled which might explain the
reports of USB stalls with THP enabled. Applying the patches brings
performance in line with THP-disabled performance while isolating
pages for immediate reclaim from the LRU cuts down System CPU time.The "Fault Alloc" success rate figures are also improved. The vanilla
kernel only managed to allocate 76.6 pages on average over the course
of 5 iterations where as applying the series allocated 181.20 on
average albeit it is well within variance. It's worth noting that
applies the series at least descreases the amount of variance which
implies an improvement.Andrea's series had a higher success rate for THP allocations but
at a severe cost to elapsed time which is still better than vanilla
but still much worse than disabling THP altogether. One can bring my
series close to Andrea's by removing this check/*
* If compaction is deferred for high-order allocations, it is because
* sync compaction recently failed. In this is the case and the caller
* has requested the system not be heavily disrupted, fail the
* allocation now instead of entering direct reclaim
*/
if (deferred_compaction && (gfp_mask & __GFP_NO_KSWAPD))
goto nopage;I didn't include a patch that removed the above check because hurting
overall performance to improve the THP figure is not what the average
user wants. It's something to consider though if someone really wants
to maximise THP usage no matter what it does to the workload initially.This is summary of vmstat figures from the same test.
3.1.0-vanilla rc5-vanilla freemore-v6r1 isolate-v6r1 andrea-v2r1
Page Ins 3257266139 1111844061 17263623 10901575 161423219
Page Outs 81054922 30364312 3626530 3657687 8753730
Swap Ins 3294 2851 6560 4964 4592
Swap Outs 390073 528094 620197 790912 698285
Direct pages scanned 1077581700 3024951463 1764930052 115140570 5901188831
Kswapd pages scanned 34826043 7112868 2131265 1686942 1893966
Kswapd pages reclaimed 28950067 4911036 1246044 966475 1497726
Direct pages reclaimed 805148398 280167837 3623473 2215044 40809360
Kswapd efficiency 83% 69% 58% 57% 79%
Kswapd velocity 664.399 622.521 4253.852 7304.360 751.490
Direct efficiency 74% 9% 0% 1% 0%
Direct velocity 20557.737 264745.137 3522673.849 498551.938 2341481.435
Percentage direct scans 96% 99% 99% 98% 99%
Page writes by reclaim 722646 529174 620319 791018 699198
Page writes file 332573 1080 122 106 913
Page writes anon 390073 528094 620197 790912 698285
Page reclaim immediate 0 2552514720 1635858848 111281140 5478375032
Page rescued immediate 0 0 0 87848 0
Slabs scanned 23552 23552 9216 8192 9216
Direct inode steals 231 0 0 0 0
Kswapd inode steals 0 0 0 0 0
Kswapd skipped wait 28076 786 0 61 6
THP fault alloc 609 383 753 906 1433
THP collapse alloc 12 6 0 0 6
THP splits 536 211 456 593 1136
THP fault fallback 4406 4633 4263 4110 3583
THP collapse fail 120 127 0 0 4
Compaction stalls 1810 728 623 779 3200
Compaction success 196 53 60 80 123
Compaction failures 1614 675 563 699 3077
Compaction pages moved 193158 53545 243185 333457 226688
Compaction move failure 9952 9396 16424 23676 45070The main things to look at are
1. Page In/out figures are much reduced by the series.
2. Direct page scanning is incredibly high (264745.137 pages scanned
per second on the vanilla kernel) but isolating PageReclaim pages
on their own list reduces the number of pages scanned significantly.3. The fact that "Page rescued immediate" is a positive number implies
that we sometimes race removing pages from the LRU_IMMEDIATE list
that need to be put back on a normal LRU but it happens only for
0.07% of the pages marked for immediate reclaim.writebackCPDeviceext4
3.1.0-vanilla rc5-vanilla freemore-v6r1 isolate-v6r1 andrea-v2r1
System Time 1.51 ( 0.00%) 1.77 ( -17.66%) 1.46 ( 2.92%) 1.15 ( 23.77%) 1.89 ( -25.63%)
+/- 0.27 ( 0.00%) 0.67 ( -148.52%) 0.33 ( -22.76%) 0.30 ( -11.15%) 0.19 ( 30.16%)
User Time 0.03 ( 0.00%) 0.04 ( -37.50%) 0.05 ( -62.50%) 0.07 ( -112.50%) 0.04 ( -18.75%)
+/- 0.01 ( 0.00%) 0.02 ( -146.64%) 0.02 ( -97.91%) 0.02 ( -75.59%) 0.02 ( -63.30%)
Elapsed Time 124.93 ( 0.00%) 114.49 ( 8.36%) 96.77 ( 22.55%) 27.48 ( 78.00%) 205.70 ( -64.65%)
+/- 20.20 ( 0.00%) 74.39 ( -268.34%) 59.88 ( -196.48%) 7.72 ( 61.79%) 25.03 ( -23.95%)
THP Active 161.80 ( 0.00%) 83.60 ( 51.67%) 141.20 ( 87.27%) 84.60 ( 52.29%) 82.60 ( 51.05%)
+/- 71.95 ( 0.00%) 43.80 ( 60.88%) 26.91 ( 37.40%) 59.02 ( 82.03%) 52.13 ( 72.45%)
Fault Alloc 471.40 ( 0.00%) 228.60 ( 48.49%) 282.20 ( 59.86%) 225.20 ( 47.77%) 388.40 ( 82.39%)
+/- 88.07 ( 0.00%) 87.42 ( 99.26%) 73.79 ( 83.78%) 109.62 ( 124.47%) 82.62 ( 93.81%)
Fault Fallback 531.60 ( 0.00%) 774.60 ( -45.71%) 720.80 ( -35.59%) 777.80 ( -46.31%) 614.80 ( -15.65%)
+/- 88.07 ( 0.00%) 87.26 ( 0.92%) 73.79 ( 16.22%) 109.62 ( -24.47%) 82.29 ( 6.56%)
MMTests Statistics: duration
User/Sys Time Running Test (seconds) 50.22 33.76 30.65 24.14 128.45
Total Elapsed Time (seconds) 1113.73 1132.19 1029.45 759.49 1707.26Similar test but the USB stick is using ext4 instead of vfat. As
ext4 does not use writepage for migration, the large stalls due to
compaction when THP is enabled are not observed. Still, isolating
PageReclaim pages on their own list helped completion time largely
by reducing the number of pages scanned by direct reclaim although
time spend in congestion_wait could also be a factor.Again, Andrea's series had far higher success rates for THP allocation
at the cost of elapsed time. I didn't look too closely but a quick
look at the vmstat figures tells me kswapd reclaimed 8 times more pages
than the patch series and direct reclaim reclaimed roughly three times
as many pages. It follows that if memory is aggressively reclaimed,
there will be more available for THP.writebackCPFilevfat
3.1.0-vanilla rc5-vanilla freemore-v6r1 isolate-v6r1 andrea-v2r1
System Time 1.76 ( 0.00%) 29.10 (-1555.52%) 46.01 (-2517.18%) 4.79 ( -172.35%) 54.89 (-3022.53%)
+/- 0.14 ( 0.00%) 25.61 (-18185.17%) 2.15 (-1434.83%) 6.60 (-4610.03%) 9.75
(-6863.76%)
User Time 0.05 ( 0.00%) 0.07 ( -45.83%) 0.05 ( -4.17%) 0.06 ( -29.17%) 0.06 ( -16.67%)
+/- 0.02 ( 0.00%) 0.02 ( 20.11%) 0.02 ( -3.14%) 0.01 ( 31.58%) 0.01 ( 47.41%)
Elapsed Time 22520.79 ( 0.00%) 1082.85 ( 95.19%) 73.30 ( 99.67%) 32.43 ( 99.86%) 291.84 ( 98.70%)
+/- 7277.23 ( 0.00%) 706.29 ( 90.29%) 19.05 ( 99.74%) 17.05 ( 99.77%) 125.55 ( 98.27%)
THP Active 83.80 ( 0.00%) 12.80 ( 15.27%) 15.60 ( 18.62%) 13.00 ( 15.51%) 0.80 ( 0.95%)
+/- 66.81 ( 0.00%) 20.19 ( 30.22%) 5.92 ( 8.86%) 15.06 ( 22.54%) 1.17 ( 1.75%)
Fault Alloc 171.00 ( 0.00%) 67.80 ( 39.65%) 97.40 ( 56.96%) 125.60 ( 73.45%) 133.00 ( 77.78%)
+/- 82.91 ( 0.00%) 30.69 ( 37.02%) 53.91 ( 65.02%) 55.05 ( 66.40%) 21.19 ( 25.56%)
Fault Fallback 832.00 ( 0.00%) 935.20 ( -12.40%) 906.00 ( -8.89%) 877.40 ( -5.46%) 870.20 ( -4.59%)
+/- 82.91 ( 0.00%) 30.69 ( 62.98%) 54.01 ( 34.86%) 55.05 ( 33.60%) 20.91 ( 74.78%)
MMTests Statistics: duration
User/Sys Time Running Test (seconds) 7229.81 928.42 704.52 80.68 1330.76
Total Elapsed Time (seconds) 112849.04 5618.69 571.11 360.54 1664.28In this case, the test is reading/writing only from filesystems but as
it's vfat, it's slow due to calling writepage during compaction. Little
to observe really - the time to complete the test goes way down
with the series applied and THP allocation success rates go up in
comparison to 3.2-rc5. The success rates are lower than 3.1.0 but
the elapsed time for that kernel is abysmal so it is not really a
sensible comparison.As before, Andrea's series allocates more THPs at the cost of overall
performance.writebackCPFileext4
3.1.0-vanilla rc5-vanilla freemore-v6r1 isolate-v6r1 andrea-v2r1
System Time 1.51 ( 0.00%) 1.77 ( -17.66%) 1.46 ( 2.92%) 1.15 ( 23.77%) 1.89 ( -25.63%)
+/- 0.27 ( 0.00%) 0.67 ( -148.52%) 0.33 ( -22.76%) 0.30 ( -11.15%) 0.19 ( 30.16%)
User Time 0.03 ( 0.00%) 0.04 ( -37.50%) 0.05 ( -62.50%) 0.07 ( -112.50%) 0.04 ( -18.75%)
+/- 0.01 ( 0.00%) 0.02 ( -146.64%) 0.02 ( -97.91%) 0.02 ( -75.59%) 0.02 ( -63.30%)
Elapsed Time 124.93 ( 0.00%) 114.49 ( 8.36%) 96.77 ( 22.55%) 27.48 ( 78.00%) 205.70 ( -64.65%)
+/- 20.20 ( 0.00%) 74.39 ( -268.34%) 59.88 ( -196.48%) 7.72 ( 61.79%) 25.03 ( -23.95%)
THP Active 161.80 ( 0.00%) 83.60 ( 51.67%) 141.20 ( 87.27%) 84.60 ( 52.29%) 82.60 ( 51.05%)
+/- 71.95 ( 0.00%) 43.80 ( 60.88%) 26.91 ( 37.40%) 59.02 ( 82.03%) 52.13 ( 72.45%)
Fault Alloc 471.40 ( 0.00%) 228.60 ( 48.49%) 282.20 ( 59.86%) 225.20 ( 47.77%) 388.40 ( 82.39%)
+/- 88.07 ( 0.00%) 87.42 ( 99.26%) 73.79 ( 83.78%) 109.62 ( 124.47%) 82.62 ( 93.81%)
Fault Fallback 531.60 ( 0.00%) 774.60 ( -45.71%) 720.80 ( -35.59%) 777.80 ( -46.31%) 614.80 ( -15.65%)
+/- 88.07 ( 0.00%) 87.26 ( 0.92%) 73.79 ( 16.22%) 109.62 ( -24.47%) 82.29 ( 6.56%)
MMTests Statistics: duration
User/Sys Time Running Test (seconds) 50.22 33.76 30.65 24.14 128.45
Total Elapsed Time (seconds) 1113.73 1132.19 1029.45 759.49 1707.26Same type of story - elapsed times go down. In this case, allocation
success rates are roughtly the same. As before, Andrea's has higher
success rates but takes a lot longer.Overall the series does reduce latencies and while the tests are
inherency racy as alloc competes with the cp processes, the variability
was included. The THP allocation rates are not as high as they could
be but that is because we would have to be more aggressive about
reclaim and compaction impacting overall performance.This patch:
Commit 39deaf85 ("mm: compaction: make isolate_lru_page() filter-aware")
noted that compaction does not migrate dirty or writeback pages and that
is was meaningless to pick the page and re-add it to the LRU list.What was missed during review is that asynchronous migration moves dirty
pages if their ->migratepage callback is migrate_page() because these can
be moved without blocking. This potentially impacted hugepage allocation
success rates by a factor depending on how many dirty pages are in the
system.This patch partially reverts 39deaf85 to allow migration to isolate dirty
pages again. This increases how much compaction disrupts the LRU but that
is addressed later in the series.Signed-off-by: Mel Gorman
Reviewed-by: Andrea Arcangeli
Reviewed-by: Rik van Riel
Reviewed-by: Minchan Kim
Cc: Dave Jones
Cc: Jan Kara
Cc: Andy Isaacson
Cc: Nai Xia
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In trace_mm_vmscan_lru_isolate(), we don't output 'file' information to
the trace event and it is a bit inconvenient for the user to get the
real information(like pasted below). mm_vmscan_lru_isolate:
isolate_mode=2 order=0 nr_requested=32 nr_scanned=32 nr_taken=32
contig_taken=0 contig_dirty=0 contig_failed=0'active' can be obtained by analyzing mode(Thanks go to Minchan and
Mel), So this patch adds 'file' to the trace event and it now looks
like: mm_vmscan_lru_isolate: isolate_mode=2 order=0 nr_requested=32
nr_scanned=32 nr_taken=32 contig_taken=0 contig_dirty=0 contig_failed=0
file=0Signed-off-by: Tao Ma
Acked-by: KOSAKI Motohiro
Reviewed-by: KAMEZAWA Hiroyuki
Cc: Mel Gorman
Reviewed-by: Minchan Kim
Cc: Rik van Riel
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Put the tail subpages of an isolated hugepage under splitting in the lru
reclaim head as they supposedly should be isolated too next.Queues the subpages in physical order in the lru for non isolated
hugepages under splitting. That might provide some theoretical cache
benefit to the buddy allocator later.Signed-off-by: Shaohua Li
Signed-off-by: Andrea Arcangeli
Cc: David Rientjes
Cc: Johannes Weiner
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We have tlb_remove_tlb_entry to indicate a pte tlb flush entry should be
flushed, but not a corresponding API for pmd entry. This isn't a
problem so far because THP is only for x86 currently and tlb_flush()
under x86 will flush entire TLB. But this is confusion and could be
missed if thp is ported to other arch.Also convert tlb->need_flush = 1 to a VM_BUG_ON(!tlb->need_flush) in
__tlb_remove_page() as suggested by Andrea Arcangeli. The
__tlb_remove_page() function is supposed to be called after
tlb_remove_xxx_tlb_entry() and we can catch any misuse.Signed-off-by: Shaohua Li
Reviewed-by: Andrea Arcangeli
Cc: David Rientjes
Cc: Johannes Weiner
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
change_protection() will do TLB flush later, don't need duplicate tlb
flush.Signed-off-by: Shaohua Li
Reviewed-by: Andrea Arcangeli
Cc: David Rientjes
Cc: Johannes Weiner
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Improve the error code path. Delete unnecessary sysfs file for example.
Also remove the #ifdef xxx to make code better.Signed-off-by: Shaohua Li
Reviewed-by: Andrea Arcangeli
Cc: David Rientjes
Cc: Johannes Weiner
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
No need for two CONFIG_MEMORY_HOTPLUG blocks.
Signed-off-by: Bob Liu
Acked-by: Michal Hocko
Cc: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Cc: KOSAKI Motohiro
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
If there is a zone below ZONE_NORMAL has present_pages, we can set node
state to N_NORMAL_MEMORY, no need to loop to end.Signed-off-by: Bob Liu
Acked-by: Michal Hocko
Cc: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Cc: KOSAKI Motohiro
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We already have for_each_node(node) define in nodemask.h, better to use it.
Signed-off-by: Bob Liu
Acked-by: Michal Hocko
Cc: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Cc: KOSAKI Motohiro
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Now, at LRU handling, memory cgroup needs to do complicated works to see
valid pc->mem_cgroup, which may be overwritten.This patch is for relaxing the protocol. This patch guarantees
- when pc->mem_cgroup is overwritten, page must not be on LRU.By this, LRU routine can believe pc->mem_cgroup and don't need to check
bits on pc->flags. This new rule may adds small overheads to swapin. But
in most case, lru handling gets faster.After this patch, PCG_ACCT_LRU bit is obsolete and removed.
[akpm@linux-foundation.org: remove unneeded VM_BUG_ON(), restore hannes's christmas tree]
[akpm@linux-foundation.org: clean up code comment]
[hughd@google.com: fix NULL mem_cgroup_try_charge]
Signed-off-by: KAMEZAWA Hiroyuki
Cc: Miklos Szeredi
Acked-by: Michal Hocko
Acked-by: Johannes Weiner
Cc: Ying Han
Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This is a preparation before removing a flag PCG_ACCT_LRU in page_cgroup
and reducing atomic ops/complexity in memcg LRU handling.In some cases, pages are added to lru before charge to memcg and pages
are not classfied to memory cgroup at lru addtion. Now, the lru where
the page should be added is determined a bit in page_cgroup->flags and
pc->mem_cgroup. I'd like to remove the check of flag.To handle the case pc->mem_cgroup may contain stale pointers if pages
are added to LRU before classification. This patch resets
pc->mem_cgroup to root_mem_cgroup before lru additions.[akpm@linux-foundation.org: fix CONFIG_CGROUP_MEM_CONT=n build]
[hughd@google.com: fix CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_CGROUP_MEM_RES_CTLR_SWAP=n build]
[akpm@linux-foundation.org: ksm.c needs memcontrol.h, per Michal]
[hughd@google.com: stop oops in mem_cgroup_reset_owner()]
[hughd@google.com: fix page migration to reset_owner]
Signed-off-by: KAMEZAWA Hiroyuki
Cc: Miklos Szeredi
Acked-by: Michal Hocko
Cc: Johannes Weiner
Cc: Ying Han
Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch simplifies LRU handling of racy case (memcg+SwapCache). At
charging, SwapCache tend to be on LRU already. So, before overwriting
pc->mem_cgroup, the page must be removed from LRU and added to LRU
later.This patch does
spin_lock(zone->lru_lock);
if (PageLRU(page))
remove from LRU
overwrite pc->mem_cgroup
if (PageLRU(page))
add to new LRU.
spin_unlock(zone->lru_lock);And guarantee all pages are not on LRU at modifying pc->mem_cgroup.
This patch also unfies lru handling of replace_page_cache() and
swapin.Signed-off-by: KAMEZAWA Hiroyuki
Cc: Miklos Szeredi
Acked-by: Michal Hocko
Acked-by: Johannes Weiner
Cc: Ying Han
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch is a clean up. No functional/logical changes.
Because of commit ef6a3c6311 ("mm: add replace_page_cache_page()
function") , FUSE uses replace_page_cache() instead of
add_to_page_cache(). Then, mem_cgroup_cache_charge() is not called
against FUSE's pages from splice.So now, mem_cgroup_cache_charge() gets pages that are not on the LRU
with the exception of PageSwapCache pages. For checking,
WARN_ON_ONCE(PageLRU(page)) is added.Signed-off-by: KAMEZAWA Hiroyuki
Cc: Miklos Szeredi
Acked-by: Michal Hocko
Acked-by: Johannes Weiner
Cc: Ying Han
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The oom killer relies on logic that identifies threads that have already
been oom killed when scanning the tasklist and, if found, deferring
until such threads have exited. This is done by checking for any
candidate threads that have the TIF_MEMDIE bit set.For memcg ooms, candidate threads are first found by calling
task_in_mem_cgroup() since the oom killer should not defer if there's an
oom killed thread in another memcg.Unfortunately, task_in_mem_cgroup() excludes threads if they have
detached their mm in the process of exiting so TIF_MEMDIE is never
detected for such conditions. This is different for global, mempolicy,
and cpuset oom conditions where a detached mm is only excluded after
checking for TIF_MEMDIE and deferring, if necessary, in
select_bad_process().The fix is to return true if a task has a detached mm but is still in
the memcg or its hierarchy that is currently oom. This will allow the
oom killer to appropriately defer rather than kill unnecessarily or, in
the worst case, panic the machine if nothing else is available to kill.Signed-off-by: David Rientjes
Acked-by: KOSAKI Motohiro
Cc: Johannes Weiner
Cc: Balbir Singh
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
If we are not able to allocate tree nodes for all NUMA nodes then we
should release those that were allocated.Signed-off-by: Michal Hocko
Acked-by: Johannes Weiner
Cc: Michal Hocko
Cc: Hugh Dickins
Cc: Balbir Singh
Cc: David Rientjes
Cc: Andrea Arcangeli
Cc: KAMEZAWA Hiroyuki
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There are multiple places which need to get the swap_cgroup address, so
add a helper function:static struct swap_cgroup *swap_cgroup_getsc(swp_entry_t ent,
struct swap_cgroup_ctrl **ctrl);to simplify the code.
Signed-off-by: Bob Liu
Acked-by: Michal Hocko
Acked-by: KAMEZAWA Hiroyuki
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
mem_cgroup_uncharge_page() is only called on either freshly allocated
pages without page->mapping or on rmapped PageAnon() pages. There is no
need to check for a page->mapping that is not an anon_vma.Signed-off-by: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Cc: Balbir Singh
Cc: David Rientjes
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
All callsites pass in freshly allocated pages and a valid mm. As a
result, all checks pertaining to the page's mapcount, page->mapping or the
fallback to init_mm are unneeded.Signed-off-by: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Cc: David Rientjes
Cc: Balbir Singh
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
lookup_page_cgroup() is usually used only against pages that are used in
userspace.The exception is the CONFIG_DEBUG_VM-only memcg check from the page
allocator: it can run on pages without page_cgroup descriptors allocated
when the pages are fed into the page allocator for the first time during
boot or memory hotplug.Include the array check only when CONFIG_DEBUG_VM is set and save the
unnecessary check in production kernels.Signed-off-by: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Cc: Balbir Singh
Cc: David Rientjes
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Pages have their corresponding page_cgroup descriptors set up before
they are used in userspace, and thus managed by a memory cgroup.The only time where lookup_page_cgroup() can return NULL is in the
CONFIG_DEBUG_VM-only page sanity checking code that executes while
feeding pages into the page allocator for the first time.Remove the NULL checks against lookup_page_cgroup() results from all
callsites where we know that corresponding page_cgroup descriptors must
be allocated, and add a comment to the callsite that actually does have
to check the return value.[hughd@google.com: stop oops in mem_cgroup_update_page_stat()]
Signed-off-by: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Cc: Balbir Singh
Cc: David Rientjes
Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The fault accounting functions have a single, memcg-internal user, so they
don't need to be global. In fact, their one-line bodies can be directly
folded into the caller. And since faults happen one at a time, use
this_cpu_inc() directly instead of this_cpu_add(foo, 1).Signed-off-by: Johannes Weiner
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Acked-by: Balbir Singh
Cc: David Rientjes
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Johannes Weiner
Acked-by: David Rientjes
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Cc: Balbir Singh
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The memcg argument of oom_kill_task() hasn't been used since 341aea2
'oom-kill: remove boost_dying_task_prio()'. Kill it.Signed-off-by: Johannes Weiner
Acked-by: David Rientjes
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Cc: Balbir Singh
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The two memcg stats pgpgin/pgpgout have different meaning than the ones
in vmstat, which indicates that we picked a bad naming for them.It might be late to change the stat name, but better documentation is
always helpful.Signed-off-by: Ying Han
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Johannes Weiner
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
It should be memsw.max_usage_in_bytes. This typo has been there for
a really long time.Signed-off-by: Zhu Yanhai
Acked-by: KAMEZAWA Hiroyuki
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Only the ratelimit checks themselves have to run with preemption
disabled, the resulting actions - checking for usage thresholds,
updating the soft limit tree - can and should run with preemption
enabled.Signed-off-by: Johannes Weiner
Reported-by: Yong Zhang
Tested-by: Yong Zhang
Reported-by: Luis Henriques
Tested-by: Luis Henriques
Cc: Thomas Gleixner
Cc: Steven Rostedt
Cc: Peter Zijlstra
Acked-by: KAMEZAWA Hiroyuki
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In split_huge_page(), mem_cgroup_split_huge_fixup() is called to handle
page_cgroup modifcations. It takes move_lock_page_cgroup() and modifies
page_cgroup and LRU accounting jobs and called HPAGE_PMD_SIZE - 1 times.But thinking again,
- compound_lock() is held at move_accout...then, it's not necessary
to take move_lock_page_cgroup().
- LRU is locked and all tail pages will go into the same LRU as
head is now on.
- page_cgroup is contiguous in huge page range.This patch fixes mem_cgroup_split_huge_fixup() as to be called once per
hugepage and reduce costs for spliting.[akpm@linux-foundation.org: fix typo, per Michal]
Signed-off-by: KAMEZAWA Hiroyuki
Cc: Johannes Weiner
Cc: Andrea Arcangeli
Reviewed-by: Michal Hocko
Cc: Balbir Singh
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
To find the page corresponding to a certain page_cgroup, the pc->flags
encoded the node or section ID with the base array to compare the pc
pointer to.Now that the per-memory cgroup LRU lists link page descriptors directly,
there is no longer any code that knows the struct page_cgroup of a PFN
but not the struct page.[hughd@google.com: remove unused node/section info from pc->flags fix]
Signed-off-by: Johannes Weiner
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: KAMEZAWA Hiroyuki
Cc: Michal Hocko
Cc: "Kirill A. Shutemov"
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Now that all code that operated on global per-zone LRU lists is
converted to operate on per-memory cgroup LRU lists instead, there is no
reason to keep the double-LRU scheme around any longer.The pc->lru member is removed and page->lru is linked directly to the
per-memory cgroup LRU lists, which removes two pointers from a
descriptor that exists for every page frame in the system.Signed-off-by: Johannes Weiner
Signed-off-by: Hugh Dickins
Signed-off-by: Ying Han
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Having a unified structure with a LRU list set for both global zones and
per-memcg zones allows to keep that code simple which deals with LRU
lists and does not care about the container itself.Once the per-memcg LRU lists directly link struct pages, the isolation
function and all other list manipulations are shared between the memcg
case and the global LRU case.Signed-off-by: Johannes Weiner
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The global per-zone LRU lists are about to go away on memcg-enabled
kernels, global reclaim must be able to find its pages on the per-memcg
LRU lists.Since the LRU pages of a zone are distributed over all existing memory
cgroups, a scan target for a zone is complete when all memory cgroups
are scanned for their proportional share of a zone's memory.The forced scanning of small scan targets from kswapd is limited to
zones marked unreclaimable, otherwise kswapd can quickly overreclaim by
force-scanning the LRU lists of multiple memory cgroups.Signed-off-by: Johannes Weiner
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
root_mem_cgroup, lacking a configurable limit, was never subject to
limit reclaim, so the pages charged to it could be kept off its LRU
lists. They would be found on the global per-zone LRU lists upon
physical memory pressure and it made sense to avoid uselessly linking
them to both lists.The global per-zone LRU lists are about to go away on memcg-enabled
kernels, with all pages being exclusively linked to their respective
per-memcg LRU lists. As a result, pages of the root_mem_cgroup must
also be linked to its LRU lists again. This is purely about the LRU
list, root_mem_cgroup is still not charged.The overhead is temporary until the double-LRU scheme is going away
completely.Signed-off-by: Johannes Weiner
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Memory cgroup limit reclaim and traditional global pressure reclaim will
soon share the same code to reclaim from a hierarchical tree of memory
cgroups.In preparation of this, move the two right next to each other in
shrink_zone().The mem_cgroup_hierarchical_reclaim() polymath is split into a soft
limit reclaim function, which still does hierarchy walking on its own,
and a limit (shrinking) reclaim function, which relies on generic
reclaim code to walk the hierarchy.Signed-off-by: Johannes Weiner
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Memory cgroup limit reclaim currently picks one memory cgroup out of the
target hierarchy, remembers it as the last scanned child, and reclaims
all zones in it with decreasing priority levels.The new hierarchy reclaim code will pick memory cgroups from the same
hierarchy concurrently from different zones and priority levels, it
becomes necessary that hierarchy roots not only remember the last
scanned child, but do so for each zone and priority level.Until now, we reclaimed memcgs like this:
mem = mem_cgroup_iter(root)
for each priority level:
for each zone in zonelist:
reclaim(mem, zone)But subsequent patches will move the memcg iteration inside the loop
over the zones:for each priority level:
for each zone in zonelist:
mem = mem_cgroup_iter(root)
reclaim(mem, zone)And to keep with the original scan order - memcg -> priority -> zone -
the last scanned memcg has to be remembered per zone and per priority
level.Furthermore, global reclaim will be switched to the hierarchy walk as
well. Different from limit reclaim, which can just recheck the limit
after some reclaim progress, its target is to scan all memcgs for the
desired zone pages, proportional to the memcg size, and so reliably
detecting a full hierarchy round-trip will become crucial.Currently, the code relies on one reclaimer encountering the same memcg
twice, but that is error-prone with concurrent reclaimers. Instead, use
a generation counter that is increased every time the child with the
highest ID has been visited, so that reclaimers can stop when the
generation changes.Signed-off-by: Johannes Weiner
Reviewed-by: Kirill A. Shutemov
Cc: KAMEZAWA Hiroyuki
Cc: Michal Hocko
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Memory cgroup hierarchies are currently handled completely outside of
the traditional reclaim code, which is invoked with a single memory
cgroup as an argument for the whole call stack.Subsequent patches will switch this code to do hierarchical reclaim, so
there needs to be a distinction between a) the memory cgroup that is
triggering reclaim due to hitting its limit and b) the memory cgroup
that is being scanned as a child of a).This patch introduces a struct mem_cgroup_zone that contains the
combination of the memory cgroup and the zone being scanned, which is
then passed down the stack instead of the zone argument.[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Johannes Weiner
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The traditional zone reclaim code is scanning the per-zone LRU lists
during direct reclaim and kswapd, and the per-zone per-memory cgroup LRU
lists when reclaiming on behalf of a memory cgroup limit.Subsequent patches will convert the traditional reclaim code to reclaim
exclusively from the per-memory cgroup LRU lists. As a result, using
the predicate for which LRU list is scanned will no longer be
appropriate to tell global reclaim from limit reclaim.This patch adds a global_reclaim() predicate to tell direct/kswapd
reclaim from memory cgroup limit reclaim and substitutes it in all
places where currently scanning_global_lru() is used for that.Signed-off-by: Johannes Weiner
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: Michal Hocko
Reviewed-by: Kirill A. Shutemov
Cc: Daisuke Nishimura
Cc: Balbir Singh
Cc: Ying Han
Cc: Greg Thelen
Cc: Michel Lespinasse
Cc: Rik van Riel
Cc: Minchan Kim
Cc: Christoph Hellwig
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
