On 4/26/2023 11:33 PM, Mel Gorman wrote:
On Wed, Apr 26, 2023 at 05:10:14PM +0200, Vlastimil Babka wrote:
On 4/26/23 17:03, Baolin Wang wrote:
This reverts commit 95e7a450b8190673675836bfef236262ceff084a.
When I tested thpscale with v6.3 kernel, I found the compaction efficiency
had a great regression compared to v6.2-rc1 kernel. See below numbers:
v6.2-rc v6.3
Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%)
Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%)
Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%)
Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%)
Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%)
Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%)
Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%)
Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%)
Ops Compaction stalls 113790.00 207099.00
Ops Compaction success 33983.00 19488.00
Ops Compaction failures 79807.00 187611.00
Ops Compaction efficiency 29.86 9.41
After some investigation, I found the commit 95e7a450b819
("Revert mm/compaction: fix set skip in fast_find_migrateblock") caused
the regression. This commit revert the commit 7efc3b726103 ("mm/compaction:
fix set skip in fast_find_migrateblock") to fix a CPU stalling issue, which
is caused by compaction stucked in repeating fast_find_migrateblock().
And now the compaction stalling issue is addressed by commit cfccd2e63e7e
("mm, compaction: finish pageblocks on complete migration failure"). So
IIRC at that time I was pointing out some scenarios that could make the
problem appear even after that commit, and we wanted to revisit that
when Mel is back.
Ah, I missed that, and will check previous discussion.
Yes, I've prototyped the fix against 6.3-rc7 and the revert is at the
end but the revert on its own has the potential for causing problems. The
series needs to be rebased, retested and posted. What I last tested
should show up shortly at
https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/ mm-follupfastmigrate-v1r1
Thanks.
