Revert "mm/compaction: fix set skip in fast_find_migrateblock"
authorVlastimil Babka <vbabka@suse.cz>
Fri, 13 Jan 2023 17:33:45 +0000 (18:33 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 1 Feb 2023 07:34:49 +0000 (08:34 +0100)
commite1275a6b2d993b92a7202b1154b4b6a7cf745646
tree597caf36f9c5452db6826f3f2f786a3f8f3bb7e5
parent2fd712538d68a738349d48b34bac99c996afc023
Revert "mm/compaction: fix set skip in fast_find_migrateblock"

commit 95e7a450b8190673675836bfef236262ceff084a upstream.

This reverts commit 7efc3b7261030da79001c00d92bc3392fd6c664c.

We have got openSUSE reports (Link 1) for 6.1 kernel with khugepaged
stalling CPU for long periods of time.  Investigation of tracepoint data
shows that compaction is stuck in repeating fast_find_migrateblock()
based migrate page isolation, and then fails to migrate all isolated
pages.

Commit 7efc3b726103 ("mm/compaction: fix set skip in fast_find_migrateblock")
was suspected as it was merged in 6.1 and in theory can indeed remove a
termination condition for fast_find_migrateblock() under certain
conditions, as it removes a place that always marks a scanned pageblock
from being re-scanned.  There are other such places, but those can be
skipped under certain conditions, which seems to match the tracepoint
data.

Testing of revert also appears to have resolved the issue, thus revert
the commit until a more robust solution for the original problem is
developed.

It's also likely this will fix qemu stalls with 6.1 kernel reported in
Link 2, but that is not yet confirmed.

Link: https://bugzilla.suse.com/show_bug.cgi?id=1206848
Link: https://lore.kernel.org/kvm/b8017e09-f336-3035-8344-c549086c2340@kernel.org/
Link: https://lore.kernel.org/lkml/20230125134434.18017-1-mgorman@techsingularity.net/
Fixes: 7efc3b726103 ("mm/compaction: fix set skip in fast_find_migrateblock")
Cc: <stable@vger.kernel.org>
Tested-by: Pedro Falcato <pedro.falcato@gmail.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mm/compaction.c