tree 440628c98f848ab7725ae7e9783bd1f2807ca7ef
parent f7b49c5d57669dee419fe2ef926da0aea84d46eb
author Darrick J. Wong <djwong@kernel.org> 1641507205 -0800
committer Darrick J. Wong <djwong@kernel.org> 1650341051 -0700

xfs: speed up rmap lookups by using non-overlapped lookups when possible

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@kernel.org>