diff mbox series

[v2,4/6] xfs: limit maxlen based on available space in xfs_rtallocate_extent_near()

Message ID 913fd7a759f56ba07a6b7eaa3894d14842167ed8.1693950248.git.osandov@osandov.com (mailing list archive)
State Superseded, archived
Headers show
Series xfs: CPU usage optimizations for realtime allocator | expand

Commit Message

Omar Sandoval Sept. 5, 2023, 9:51 p.m. UTC 
From: Omar Sandoval <osandov@fb.com>

xfs_rtallocate_extent_near() calls xfs_rtallocate_extent_block() with
the minlen and maxlen that were passed to it.
xfs_rtallocate_extent_block() then scans the bitmap block looking for a
free range of size maxlen. If there is none, it has to scan the whole
bitmap block before returning the largest range of at least size minlen.
For a fragmented realtime device and a large allocation request, it's
almost certain that this will have to search the whole bitmap block,
leading to high CPU usage.

However, the realtime summary tells us the maximum size available in the
bitmap block. We can limit the search in xfs_rtallocate_extent_block()
to that size and often stop before scanning the whole bitmap block.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 fs/xfs/xfs_rtalloc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Comments

Christoph Hellwig Oct. 9, 2023, 10:36 a.m. UTC | #1 
Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 13fa0ce91376..24c517595ded 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -491,6 +491,9 @@  xfs_rtallocate_extent_near(
 		 * allocating one.
 		 */
 		if (maxlog >= 0) {
+			xfs_extlen_t maxavail =
+				min_t(xfs_rtblock_t, maxlen,
+				      (1ULL << (maxlog + 1)) - 1);
 			/*
 			 * On the positive side of the starting location.
 			 */
@@ -500,7 +503,7 @@  xfs_rtallocate_extent_near(
 				 * this block.
 				 */
 				error = xfs_rtallocate_extent_block(mp, tp,
-					bbno + i, minlen, maxlen, len, &n,
+					bbno + i, minlen, maxavail, len, &n,
 					rtbufc, prod, &r);
 				if (error) {
 					return error;
@@ -545,7 +548,7 @@  xfs_rtallocate_extent_near(
 					if (maxlog >= 0)
 						continue;
 					error = xfs_rtallocate_extent_block(mp,
-						tp, bbno + j, minlen, maxlen,
+						tp, bbno + j, minlen, maxavail,
 						len, &n, rtbufc, prod, &r);
 					if (error) {
 						return error;
@@ -567,7 +570,7 @@  xfs_rtallocate_extent_near(
 				 * that we found.
 				 */
 				error = xfs_rtallocate_extent_block(mp, tp,
-					bbno + i, minlen, maxlen, len, &n,
+					bbno + i, minlen, maxavail, len, &n,
 					rtbufc, prod, &r);
 				if (error) {
 					return error;