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  1. 23 4月, 2020 15 次提交
    • M
      mm, compaction: finish pageblock scanning on contention · 4bfbd121
      由 Mel Gorman 提交于 
      to #26255339

commit cb2dcaf023c2cf12d45289c82d4030d33f7df73e upstream

Async migration aborts on spinlock contention but contention can be high
when there are multiple compaction attempts and kswapd is active.  The
consequence is that the migration scanners move forward uselessly while
still contending on locks for longer while leaving suitable migration
sources behind.

This patch will acquire the lock but track when contention occurs.  When
it does, the current pageblock will finish as compaction may succeed for
that block and then abort.  This will have a variable impact on latency
as in some cases useless scanning is avoided (reduces latency) but a
lock will be contended (increase latency) or a single contended
pageblock is scanned that would otherwise have been skipped (increase
latency).

                                     5.0.0-rc1              5.0.0-rc1
                                norescan-v3r16    finishcontend-v3r16
Amean     fault-both-1         0.00 (   0.00%)        0.00 *   0.00%*
Amean     fault-both-3      3002.07 (   0.00%)     3153.17 (  -5.03%)
Amean     fault-both-5      4684.47 (   0.00%)     4280.52 (   8.62%)
Amean     fault-both-7      6815.54 (   0.00%)     5811.50 *  14.73%*
Amean     fault-both-12    10864.02 (   0.00%)     9276.85 (  14.61%)
Amean     fault-both-18    12247.52 (   0.00%)    11032.67 (   9.92%)
Amean     fault-both-24    15683.99 (   0.00%)    14285.70 (   8.92%)
Amean     fault-both-30    18620.02 (   0.00%)    16293.76 *  12.49%*
Amean     fault-both-32    19250.28 (   0.00%)    16721.02 *  13.14%*

                                5.0.0-rc1              5.0.0-rc1
                           norescan-v3r16    finishcontend-v3r16
Percentage huge-1         0.00 (   0.00%)        0.00 (   0.00%)
Percentage huge-3        95.00 (   0.00%)       96.82 (   1.92%)
Percentage huge-5        94.22 (   0.00%)       95.40 (   1.26%)
Percentage huge-7        92.35 (   0.00%)       95.92 (   3.86%)
Percentage huge-12       91.90 (   0.00%)       96.73 (   5.25%)
Percentage huge-18       89.58 (   0.00%)       96.77 (   8.03%)
Percentage huge-24       90.03 (   0.00%)       96.05 (   6.69%)
Percentage huge-30       89.14 (   0.00%)       96.81 (   8.60%)
Percentage huge-32       90.58 (   0.00%)       97.41 (   7.54%)

There is a variable impact that is mostly good on latency while allocation
success rates are slightly higher.  System CPU usage is reduced by about
10% but scan rate impact is mixed

Compaction migrate scanned    27997659.00    20148867
Compaction free scanned      120782791.00   118324914

Migration scan rates are reduced 28% which is expected as a pageblock is
used by the async scanner instead of skipped.  The impact on the free
scanner is known to be variable.  Overall the primary justification for
this patch is that completing scanning of a pageblock is very important
for later patches.

[yuehaibing@huawei.com: fix unused variable warning]
Link: http://lkml.kernel.org/r/20190118175136.31341-14-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: YueHaibing <yuehaibing@huawei.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      4bfbd121
    • M
      mm, compaction: avoid rescanning the same pageblock multiple times · 1586467d
      由 Mel Gorman 提交于 
      to #26255339

commit 804d3121ba5f03af0ab225e2f688ee3ee669c0d2 upstream

Pageblocks are marked for skip when no pages are isolated after a scan.
However, it's possible to hit corner cases where the migration scanner
gets stuck near the boundary between the source and target scanner.  Due
to pages being migrated in blocks of COMPACT_CLUSTER_MAX, pages that are
migrated can be reallocated before the pageblock is complete.  The
pageblock is not necessarily skipped so it can be rescanned multiple
times.  Similarly, a pageblock with some dirty/writeback pages may fail
to migrate and be rescanned until writeback completes which is wasteful.

This patch tracks if a pageblock is being rescanned.  If so, then the
entire pageblock will be migrated as one operation.  This narrows the
race window during which pages can be reallocated during migration.
Secondly, if there are pages that cannot be isolated then the pageblock
will still be fully scanned and marked for skipping.  On the second
rescan, the pageblock skip is set and the migration scanner makes
progress.

                                     5.0.0-rc1              5.0.0-rc1
                                findfree-v3r16         norescan-v3r16
Amean     fault-both-1         0.00 (   0.00%)        0.00 *   0.00%*
Amean     fault-both-3      3200.68 (   0.00%)     3002.07 (   6.21%)
Amean     fault-both-5      4847.75 (   0.00%)     4684.47 (   3.37%)
Amean     fault-both-7      6658.92 (   0.00%)     6815.54 (  -2.35%)
Amean     fault-both-12    11077.62 (   0.00%)    10864.02 (   1.93%)
Amean     fault-both-18    12403.97 (   0.00%)    12247.52 (   1.26%)
Amean     fault-both-24    15607.10 (   0.00%)    15683.99 (  -0.49%)
Amean     fault-both-30    18752.27 (   0.00%)    18620.02 (   0.71%)
Amean     fault-both-32    21207.54 (   0.00%)    19250.28 *   9.23%*

                                5.0.0-rc1              5.0.0-rc1
                           findfree-v3r16         norescan-v3r16
Percentage huge-3        96.86 (   0.00%)       95.00 (  -1.91%)
Percentage huge-5        93.72 (   0.00%)       94.22 (   0.53%)
Percentage huge-7        94.31 (   0.00%)       92.35 (  -2.08%)
Percentage huge-12       92.66 (   0.00%)       91.90 (  -0.82%)
Percentage huge-18       91.51 (   0.00%)       89.58 (  -2.11%)
Percentage huge-24       90.50 (   0.00%)       90.03 (  -0.52%)
Percentage huge-30       91.57 (   0.00%)       89.14 (  -2.65%)
Percentage huge-32       91.00 (   0.00%)       90.58 (  -0.46%)

Negligible difference but this was likely a case when the specific
corner case was not hit.  A previous run of the same patch based on an
earlier iteration of the series showed large differences where migration
rates could be halved when the corner case was hit.

The specific corner case where migration scan rates go through the roof
was due to a dirty/writeback pageblock located at the boundary of the
migration/free scanner did not happen in this case.  When it does
happen, the scan rates multipled by massive margins.

Link: http://lkml.kernel.org/r/20190118175136.31341-13-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      1586467d
    • M
      mm, compaction: use free lists to quickly locate a migration target · 8eaac357
      由 Mel Gorman 提交于 
      to #26255339

commit 5a811889de10f1ebb8e03a2744be006e909c405c upstream

Similar to the migration scanner, this patch uses the free lists to
quickly locate a migration target.  The search is different in that
lower orders will be searched for a suitable high PFN if necessary but
the search is still bound.  This is justified on the grounds that the
free scanner typically scans linearly much more than the migration
scanner.

If a free page is found, it is isolated and compaction continues if
enough pages were isolated.  For SYNC* scanning, the full pageblock is
scanned for any remaining free pages so that is can be marked for
skipping in the near future.

1-socket thpfioscale
                                     5.0.0-rc1              5.0.0-rc1
                                 isolmig-v3r15         findfree-v3r16
Amean     fault-both-3      3024.41 (   0.00%)     3200.68 (  -5.83%)
Amean     fault-both-5      4749.30 (   0.00%)     4847.75 (  -2.07%)
Amean     fault-both-7      6454.95 (   0.00%)     6658.92 (  -3.16%)
Amean     fault-both-12    10324.83 (   0.00%)    11077.62 (  -7.29%)
Amean     fault-both-18    12896.82 (   0.00%)    12403.97 (   3.82%)
Amean     fault-both-24    13470.60 (   0.00%)    15607.10 * -15.86%*
Amean     fault-both-30    17143.99 (   0.00%)    18752.27 (  -9.38%)
Amean     fault-both-32    17743.91 (   0.00%)    21207.54 * -19.52%*

The impact on latency is variable but the search is optimistic and
sensitive to the exact system state.  Success rates are similar but the
major impact is to the rate of scanning

                                5.0.0-rc1      5.0.0-rc1
                            isolmig-v3r15 findfree-v3r16
Compaction migrate scanned    25646769          29507205
Compaction free scanned      201558184         100359571

The free scan rates are reduced by 50%.  The 2-socket reductions for the
free scanner are more dramatic which is a likely reflection that the
machine has more memory.

[dan.carpenter@oracle.com: fix static checker warning]
[vbabka@suse.cz: correct number of pages scanned for lower orders]
Link: http://lkml.kernel.org/r/20190118175136.31341-12-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      8eaac357
    • M
      mm, compaction: keep migration source private to a single compaction instance · 87f9b9a3
      由 Mel Gorman 提交于 
      to #26255339

commit e380bebe4771548df9bece8b7ad9dab07d9158a6 upstream

Due to either a fast search of the free list or a linear scan, it is
possible for multiple compaction instances to pick the same pageblock
for migration.  This is lucky for one scanner and increased scanning for
all the others.  It also allows a race between requests on which first
allocates the resulting free block.

This patch tests and updates the pageblock skip for the migration
scanner carefully.  When isolating a block, it will check and skip if
the block is already in use.  Once the zone lock is acquired, it will be
rechecked so that only one scanner can set the pageblock skip for
exclusive use.  Any scanner contending will continue with a linear scan.
The skip bit is still set if no pages can be isolated in a range.  While
this may result in redundant scanning, it avoids unnecessarily acquiring
the zone lock when there are no suitable migration sources.

1-socket thpscale
Amean     fault-both-1         0.00 (   0.00%)        0.00 *   0.00%*
Amean     fault-both-3      3390.40 (   0.00%)     3024.41 (  10.80%)
Amean     fault-both-5      5082.28 (   0.00%)     4749.30 (   6.55%)
Amean     fault-both-7      7012.51 (   0.00%)     6454.95 (   7.95%)
Amean     fault-both-12    11346.63 (   0.00%)    10324.83 (   9.01%)
Amean     fault-both-18    15324.19 (   0.00%)    12896.82 *  15.84%*
Amean     fault-both-24    16088.50 (   0.00%)    13470.60 *  16.27%*
Amean     fault-both-30    18723.42 (   0.00%)    17143.99 (   8.44%)
Amean     fault-both-32    18612.01 (   0.00%)    17743.91 (   4.66%)

                                5.0.0-rc1              5.0.0-rc1
                            findmig-v3r15          isolmig-v3r15
Percentage huge-3        89.83 (   0.00%)       92.96 (   3.48%)
Percentage huge-5        91.96 (   0.00%)       93.26 (   1.41%)
Percentage huge-7        92.85 (   0.00%)       93.63 (   0.84%)
Percentage huge-12       92.74 (   0.00%)       92.80 (   0.07%)
Percentage huge-18       91.71 (   0.00%)       91.62 (  -0.10%)
Percentage huge-24       92.13 (   0.00%)       91.50 (  -0.69%)
Percentage huge-30       93.79 (   0.00%)       92.73 (  -1.13%)
Percentage huge-32       91.27 (   0.00%)       91.94 (   0.74%)

This shows a reasonable reduction in latency as multiple compaction
scanners do not operate on the same blocks with a similar allocation
success rate.

Compaction migrate scanned    41093126    25646769

Migration scan rates are reduced by 38%.

Link: http://lkml.kernel.org/r/20190118175136.31341-11-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      87f9b9a3
    • M
      mm, compaction: use free lists to quickly locate a migration source · 255de7ac
      由 Mel Gorman 提交于 
      to #26255339

commit 70b44595eafe9c7c235f076d653a268ca1ab9fdb upstream

The migration scanner is a linear scan of a zone with a potentiall large
search space.  Furthermore, many pageblocks are unusable such as those
filled with reserved pages or partially filled with pages that cannot
migrate.  These still get scanned in the common case of allocating a THP
and the cost accumulates.

The patch uses a partial search of the free lists to locate a migration
source candidate that is marked as MOVABLE when allocating a THP.  It
prefers picking a block with a larger number of free pages already on
the basis that there are fewer pages to migrate to free the entire
block.  The lowest PFN found during searches is tracked as the basis of
the start for the linear search after the first search of the free list
fails.  After the search, the free list is shuffled so that the next
search will not encounter the same page.  If the search fails then the
subsequent searches will be shorter and the linear scanner is used.

If this search fails, or if the request is for a small or
unmovable/reclaimable allocation then the linear scanner is still used.
It is somewhat pointless to use the list search in those cases.  Small
free pages must be used for the search and there is no guarantee that
movable pages are located within that block that are contiguous.

                                     5.0.0-rc1              5.0.0-rc1
                                 noboost-v3r10          findmig-v3r15
Amean     fault-both-3      3771.41 (   0.00%)     3390.40 (  10.10%)
Amean     fault-both-5      5409.05 (   0.00%)     5082.28 (   6.04%)
Amean     fault-both-7      7040.74 (   0.00%)     7012.51 (   0.40%)
Amean     fault-both-12    11887.35 (   0.00%)    11346.63 (   4.55%)
Amean     fault-both-18    16718.19 (   0.00%)    15324.19 (   8.34%)
Amean     fault-both-24    21157.19 (   0.00%)    16088.50 *  23.96%*
Amean     fault-both-30    21175.92 (   0.00%)    18723.42 *  11.58%*
Amean     fault-both-32    21339.03 (   0.00%)    18612.01 *  12.78%*

                                5.0.0-rc1              5.0.0-rc1
                            noboost-v3r10          findmig-v3r15
Percentage huge-3        86.50 (   0.00%)       89.83 (   3.85%)
Percentage huge-5        92.52 (   0.00%)       91.96 (  -0.61%)
Percentage huge-7        92.44 (   0.00%)       92.85 (   0.44%)
Percentage huge-12       92.98 (   0.00%)       92.74 (  -0.25%)
Percentage huge-18       91.70 (   0.00%)       91.71 (   0.02%)
Percentage huge-24       91.59 (   0.00%)       92.13 (   0.60%)
Percentage huge-30       90.14 (   0.00%)       93.79 (   4.04%)
Percentage huge-32       90.03 (   0.00%)       91.27 (   1.37%)

This shows an improvement in allocation latencies with similar
allocation success rates.  While not presented, there was a 31%
reduction in migration scanning and a 8% reduction on system CPU usage.
A 2-socket machine showed similar benefits.

[mgorman@techsingularity.net: several fixes]
  Link: http://lkml.kernel.org/r/20190204120111.GL9565@techsingularity.net
[vbabka@suse.cz: migrate block that was found-fast, some optimisations]
Link: http://lkml.kernel.org/r/20190118175136.31341-10-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <Vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      255de7ac
    • M
      mm, compaction: ignore the fragmentation avoidance boost for isolation and compaction · a7ff78ca
      由 Mel Gorman 提交于 
      to #26255339

commit fd1444b2729289ea3ef6b6096be604f8983e9f9f upstream

When pageblocks get fragmented, watermarks are artifically boosted to
reclaim pages to avoid further fragmentation events.  However,
compaction is often either fragmentation-neutral or moving movable pages
away from unmovable/reclaimable pages.  As the true watermarks are
preserved, allow compaction to ignore the boost factor.

The expected impact is very slight as the main benefit is that
compaction is slightly more likely to succeed when the system has been
fragmented very recently.  On both 1-socket and 2-socket machines for
THP-intensive allocation during fragmentation the success rate was
increased by less than 1% which is marginal.  However, detailed tracing
indicated that failure of migration due to a premature ENOMEM triggered
by watermark checks were eliminated.

Link: http://lkml.kernel.org/r/20190118175136.31341-9-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      a7ff78ca
    • M
      mm, compaction: always finish scanning of a full pageblock · d3a528a2
      由 Mel Gorman 提交于 
      to #26255339

commit efe771c7603bc524425070d651e70e9c56c57f28 upstream

When compaction is finishing, it uses a flag to ensure the pageblock is
complete but it makes sense to always complete migration of a pageblock.
Minimally, skip information is based on a pageblock and partially
scanned pageblocks may incur more scanning in the future.  The pageblock
skip handling also becomes more strict later in the series and the hint
is more useful if a complete pageblock was always scanned.

The potentially impacts latency as more scanning is done but it's not a
consistent win or loss as the scanning is not always a high percentage
of the pageblock and sometimes it is offset by future reductions in
scanning.  Hence, the results are not presented this time due to a
misleading mix of gains/losses without any clear pattern.  However, full
scanning of the pageblock is important for later patches.

Link: http://lkml.kernel.org/r/20190118175136.31341-8-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      d3a528a2
    • M
      mm, migrate: immediately fail migration of a page with no migration handler · bed49b98
      由 Mel Gorman 提交于 
      to #26255339

commit 806031bb5ec36ed879d64249d5a5cf9c6657f89d upstream

Pages with no migration handler use a fallback handler which sometimes
works and sometimes persistently retries.  A historical example was
blockdev pages but there are others such as odd refcounting when
page->private is used.  These are retried multiple times which is
wasteful during compaction so this patch will fail migration faster
unless the caller specifies MIGRATE_SYNC.

This is not expected to help THP allocation success rates but it did
reduce latencies very slightly in some cases.

1-socket thpfioscale
                                        4.20.0                 4.20.0
                              noreserved-v2r15         failfast-v2r15
Amean     fault-both-1         0.00 (   0.00%)        0.00 *   0.00%*
Amean     fault-both-3      3839.67 (   0.00%)     3833.72 (   0.15%)
Amean     fault-both-5      5177.47 (   0.00%)     4967.15 (   4.06%)
Amean     fault-both-7      7245.03 (   0.00%)     7139.19 (   1.46%)
Amean     fault-both-12    11534.89 (   0.00%)    11326.30 (   1.81%)
Amean     fault-both-18    16241.10 (   0.00%)    16270.70 (  -0.18%)
Amean     fault-both-24    19075.91 (   0.00%)    19839.65 (  -4.00%)
Amean     fault-both-30    22712.11 (   0.00%)    21707.05 (   4.43%)
Amean     fault-both-32    21692.92 (   0.00%)    21968.16 (  -1.27%)

The 2-socket results are not materially different.  Scan rates are
similar as expected.

Link: http://lkml.kernel.org/r/20190118175136.31341-7-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      bed49b98
    • M
      mm, compaction: rename map_pages to split_map_pages · 47ee435b
      由 Mel Gorman 提交于 
      to #26255339

commit 4469ab98477b290f6728b79f8d225d9d88ce16e3 upstream

It's non-obvious that high-order free pages are split into order-0 pages
from the function name.  Fix it.

Link: http://lkml.kernel.org/r/20190118175136.31341-6-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      47ee435b
    • M
      mm, compaction: remove unnecessary zone parameter in some instances · 66dfb67e
      由 Mel Gorman 提交于 
      to #26255339

commit 40cacbcb324036233a927418441323459d28d19b upstream

A zone parameter is passed into a number of top-level compaction
functions despite the fact that it's already in compact_control.  This
is harmless but it did need an audit to check if zone actually ever
changes meaningfully.  This patches removes the parameter in a number of
top-level functions.  The change could be much deeper but this was
enough to briefly clarify the flow.

No functional change.

Link: http://lkml.kernel.org/r/20190118175136.31341-5-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      66dfb67e
    • M
      mm, compaction: remove last_migrated_pfn from compact_control · 3e1a250c
      由 Mel Gorman 提交于 
      to #26255339

commit 566e54e113eb2b669f9300db2c2df400cbb06646 upstream

The last_migrated_pfn field is a bit dubious as to whether it really
helps but either way, the information from it can be inferred without
increasing the size of compact_control so remove the field.

Link: http://lkml.kernel.org/r/20190118175136.31341-4-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      3e1a250c
    • M
      mm, compaction: rearrange compact_control · 7f7d6863
      由 Mel Gorman 提交于 
      to #26255339

commit c5943b9c5312d4fa23175ff146e901b865e4a60a upstream

compact_control spans two cache lines with write-intensive lines on
both.  Rearrange so the most write-intensive fields are in the same
cache line.  This has a negligible impact on the overall performance of
compaction and is more a tidying exercise than anything.

Link: http://lkml.kernel.org/r/20190118175136.31341-3-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      7f7d6863
    • M
      mm, compaction: shrink compact_control · 42fbe240
      由 Mel Gorman 提交于 
      to #26255339

commit c5fbd937b603885f1db3280ca212ed28add895bc upstream

Patch series "Increase success rates and reduce latency of compaction", v3.

This series reduces scan rates and success rates of compaction,
primarily by using the free lists to shorten scans, better controlling
of skip information and whether multiple scanners can target the same
block and capturing pageblocks before being stolen by parallel requests.
The series is based on mmotm from January 9th, 2019 with the previous
compaction series reverted.

I'm mostly using thpscale to measure the impact of the series.  The
benchmark creates a large file, maps it, faults it, punches holes in the
mapping so that the virtual address space is fragmented and then tries
to allocate THP.  It re-executes for different numbers of threads.  From
a fragmentation perspective, the workload is relatively benign but it
does stress compaction.

The overall impact on latencies for a 1-socket machine is

				      baseline		      patches
Amean     fault-both-3      3832.09 (   0.00%)     2748.56 *  28.28%*
Amean     fault-both-5      4933.06 (   0.00%)     4255.52 (  13.73%)
Amean     fault-both-7      7017.75 (   0.00%)     6586.93 (   6.14%)
Amean     fault-both-12    11610.51 (   0.00%)     9162.34 *  21.09%*
Amean     fault-both-18    17055.85 (   0.00%)    11530.06 *  32.40%*
Amean     fault-both-24    19306.27 (   0.00%)    17956.13 (   6.99%)
Amean     fault-both-30    22516.49 (   0.00%)    15686.47 *  30.33%*
Amean     fault-both-32    23442.93 (   0.00%)    16564.83 *  29.34%*

The allocation success rates are much improved

			 	 baseline		 patches
Percentage huge-3        85.99 (   0.00%)       97.96 (  13.92%)
Percentage huge-5        88.27 (   0.00%)       96.87 (   9.74%)
Percentage huge-7        85.87 (   0.00%)       94.53 (  10.09%)
Percentage huge-12       82.38 (   0.00%)       98.44 (  19.49%)
Percentage huge-18       83.29 (   0.00%)       99.14 (  19.04%)
Percentage huge-24       81.41 (   0.00%)       97.35 (  19.57%)
Percentage huge-30       80.98 (   0.00%)       98.05 (  21.08%)
Percentage huge-32       80.53 (   0.00%)       97.06 (  20.53%)

That's a nearly perfect allocation success rate.

The biggest impact is on the scan rates

Compaction migrate scanned    55893379    19341254
Compaction free scanned      474739990    11903963

The number of pages scanned for migration was reduced by 65% and the
free scanner was reduced by 97.5%.  So much less work in exchange for
lower latency and better success rates.

The series was also evaluated using a workload that heavily fragments
memory but the benefits there are also significant, albeit not
presented.

It was commented that we should be rethinking scanning entirely and to a
large extent I agree.  However, to achieve that you need a lot of this
series in place first so it's best to make the linear scanners as best
as possible before ripping them out.

This patch (of 22):

The isolate and migrate scanners should never isolate more than a
pageblock of pages so unsigned int is sufficient saving 8 bytes on a
64-bit build.

Link: http://lkml.kernel.org/r/20190118175136.31341-2-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      42fbe240
    • M
      mm: move zone watermark accesses behind an accessor · 1bb2b85e
      由 Mel Gorman 提交于 
      to #26255339

commit a921444382b49cc7fdeca3fba3e278bc09484a27 upstream

This is a preparation patch only, no functional change.

Link: http://lkml.kernel.org/r/20181123114528.28802-3-mgorman@techsingularity.netSigned-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      1bb2b85e
    • Y
      alinux: Revert "mm/compaction.c: clear total_{migrate,free}_scanned before scanning a new zone" · b725e258
      由 Yang Shi 提交于 
      to #26255339

This reverts commit 4d8bdf7f.

The commit was backported from v5.4 to stable tree, but it breaks the
context depended by backporting compaction optimization made in v5.1.
So revert this commit for now, the commit will be re-applied after the
compaction optimization series.
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
      b725e258
  3. 22 4月, 2020 25 次提交