From 1fe5c2aa3903d911b9b15c8278e4442323a3a95a Mon Sep 17 00:00:00 2001 From: Chi Zhiling Date: Wed, 5 Feb 2025 13:40:23 -0800 Subject: [PATCH] xfs: Reduce unnecessary searches when searching for the best extents commit 3ef22684038aa577c10972ee9c6a2455f5fac941 upstream. Recently, we found that the CPU spent a lot of time in xfs_alloc_ag_vextent_size when the filesystem has millions of fragmented spaces. The reason is that we conducted much extra searching for extents that could not yield a better result, and these searches would cost a lot of time when there were millions of extents to search through. Even if we get the same result length, we don't switch our choice to the new one, so we can definitely terminate the search early. Since the result length cannot exceed the found length, when the found length equals the best result length we already have, we can conclude the search. We did a test in that filesystem: [root@localhost ~]# xfs_db -c freesp /dev/vdb from to extents blocks pct 1 1 215 215 0.01 2 3 994476 1988952 99.99 Before this patch: 0) | xfs_alloc_ag_vextent_size [xfs]() { 0) * 15597.94 us | } After this patch: 0) | xfs_alloc_ag_vextent_size [xfs]() { 0) 19.176 us | } Signed-off-by: Chi Zhiling Reviewed-by: Dave Chinner Signed-off-by: Carlos Maiolino Signed-off-by: Catherine Hoang Acked-by: Darrick J. Wong Signed-off-by: Greg Kroah-Hartman --- fs/xfs/libxfs/xfs_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index d8081095557c..ad2fa3c26f8a 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c @@ -1783,7 +1783,7 @@ restart: error = -EFSCORRUPTED; goto error0; } - if (flen < bestrlen) + if (flen <= bestrlen) break; busy = xfs_alloc_compute_aligned(args, fbno, flen, &rbno, &rlen, &busy_gen);