Re: [PATCH 3/4] xfs: speed up rmap lookups by using non-overlapped lookups when possible

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On Tue, Apr 26, 2022 at 05:51:42PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
> 
> Reverse mapping on a reflink-capable filesystem has some pretty high
> overhead when performing file operations.  This is because the rmap
> records for logically and physically adjacent extents might not be
> adjacent in the rmap index due to data block sharing.  As a result, we
> use expensive overlapped-interval btree search, which walks every record
> that overlaps with the supplied key in the hopes of finding the record.
> 
> However, profiling data shows that when the index contains a record that
> is an exact match for a query key, the non-overlapped btree search
> function can find the record much faster than the overlapped version.
> Try the non-overlapped lookup first, which will make scrub run much
> faster.
> 
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>

LGTM.

Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>

-- 
Dave Chinner
david@xxxxxxxxxxxxx



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