xfs: stagger the starting AG of scrub iscans to reduce contention

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Online directory and parent repairs on parent-pointer equipped
filesystems have shown that starting a large number of parallel iscans
causes a lot of AGI buffer contention.  Try to reduce this by making it
so that iscans scan wrap around the end of the filesystem, and using a
rotor to stagger where each scanner begins.  Surprisingly, this boosts
CPU utilization (on the author's test machines) from effectively
single-threaded to 160%.  Not great, but see the next patch.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

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Darrick J. Wong 2024-02-22 12:30:46 -08:00

parent 4e98cc905c

commit c473a3320b

3 changed files with 89 additions and 12 deletions

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89

fs/xfs/scrub/iscan.c

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7

fs/xfs/scrub/iscan.h

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7

fs/xfs/scrub/trace.h

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