[PATCHSET,0/4] xfs: fix rmap inefficiencies

Message

Darrick J. Wong April 14, 2022, 10:53 p.m. UTC

Hi all,

Reduce the performance impact of the reverse mapping btree when reflink
is enabled by using the much faster non-overlapped btree lookup
functions when we're searching the rmap index with a fully specified
key.  If we find the exact record we're looking for, great!  We don't
have to perform the full overlapped scan.  For filesystems with high
sharing factors this reduces the xfs_scrub runtime by a good 15%.

This has been shown to reduce the fstests runtime for realtime rmap
configurations by 30%, since the lack of AGs severely limits
scalability.

If you're going to start using this mess, you probably ought to just
pull from my git trees, which are linked below.

This is an extraordinary way to destroy everything.  Enjoy!
Comments and questions are, as always, welcome.

--D

kernel git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=rmap-speedups-5.19
---
 fs/xfs/libxfs/xfs_rmap.c |  132 +++++++++++++++++++++++++++++-----------------
 fs/xfs/libxfs/xfs_rmap.h |    7 +-
 fs/xfs/scrub/bmap.c      |   24 +-------
 fs/xfs/xfs_trace.h       |    5 +-
 4 files changed, 94 insertions(+), 74 deletions(-)