diff mbox series

[9/9] xfs: don't look for end of extent further than necessary in xfs_rtallocate_extent_near()

Message ID 169773211863.225862.16145960977172771711.stgit@frogsfrogsfrogs (mailing list archive)
State Deferred, archived
Headers show
Series xfs: CPU usage optimizations for realtime allocator | expand

Commit Message

Darrick J. Wong Oct. 19, 2023, 4:30 p.m. UTC 
From: Omar Sandoval <osandov@fb.com>

As explained in the previous commit, xfs_rtallocate_extent_near() looks
for the end of a free extent when searching backwards from the target
bitmap block. Since the previous commit, it searches from the last
bitmap block it checked to the bitmap block containing the start of the
extent.

This may still be more than necessary, since the free extent may not be
that long. We know the maximum size of the free extent from the realtime
summary. Use that to compute how many bitmap blocks we actually need to
check.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_rtalloc.c |   27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index b743da885ed6..ba66442910b1 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -527,13 +527,30 @@  xfs_rtallocate_extent_near(
 			 * On the negative side of the starting location.
 			 */
 			else {		/* i < 0 */
+				int	maxblocks;
+
 				/*
-				 * Loop backwards through the bitmap blocks
-				 * from where we last checked down to where we
-				 * are now.  There should be an extent which
-				 * ends in this bitmap block and is long
-				 * enough.
+				 * Loop backwards to find the end of the extent
+				 * we found in the realtime summary.
+				 *
+				 * maxblocks is the maximum possible number of
+				 * bitmap blocks from the start of the extent
+				 * to the end of the extent.
 				 */
+				if (maxlog == 0)
+					maxblocks = 0;
+				else if (maxlog < mp->m_blkbit_log)
+					maxblocks = 1;
+				else
+					maxblocks = 2 << (maxlog - mp->m_blkbit_log);
+
+				/*
+				 * We need to check bbno + i + maxblocks down to
+				 * bbno + i. We already checked bbno down to
+				 * bbno + j + 1, so we don't need to check those
+				 * again.
+				 */
+				j = min(i + maxblocks, j);
 				for (; j >= i; j--) {
 					error = xfs_rtallocate_extent_block(args,
 							bbno + j, minlen,