From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> The xattr scrubber functions use the temporary memory buffer either for storing bitmaps or for testing if attribute value extraction works. The bitmap code always zeroes what it needs and the value extraction merely sets the buffer contents (we never read the contents, we just look for return codes), so it's not necessary to waste CPU time zeroing on allocation. A flame graph analysis showed that we were spending 7% of a xfs_scrub run (the whole program, not just the attr scrubber itself) allocating and zeroing 64k segments needlessly. Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --- fs/xfs/scrub/attr.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/xfs/scrub/attr.c b/fs/xfs/scrub/attr.c index 09081d8ab34b..d3a6f3dacf0d 100644 --- a/fs/xfs/scrub/attr.c +++ b/fs/xfs/scrub/attr.c @@ -64,7 +64,12 @@ xchk_setup_xattr_buf( sc->buf = NULL; } - ab = kmem_zalloc_large(sizeof(*ab) + sz, flags); + /* + * Allocate the big buffer. We skip zeroing it because that added 7% + * to the scrub runtime and all the users were careful never to read + * uninitialized contents. + */ + ab = kmem_alloc_large(sizeof(*ab) + sz, flags); if (!ab) return -ENOMEM;
