From: Chi Zhiling Date: Fri, 25 Oct 2024 02:33:20 +0000 (+0800) Subject: xfs: Reduce unnecessary searches when searching for the best extents X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3ef22684038aa577c10972ee9c6a2455f5fac941;p=users%2Fdwmw2%2Flinux.git xfs: Reduce unnecessary searches when searching for the best extents 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 --- diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index 04f64cf9777e2..22bdbb3e9980c 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c @@ -1923,7 +1923,7 @@ restart: error = -EFSCORRUPTED; goto error0; } - if (flen < bestrlen) + if (flen <= bestrlen) break; busy = xfs_alloc_compute_aligned(args, fbno, flen, &rbno, &rlen, &busy_gen);