diff options
authorAlexander Motin <mav@FreeBSD.org>2022-07-05 23:27:29 +0000
committerGitHub <noreply@github.com>2022-07-05 23:27:29 +0000
commit74230a5bc1be6e5e84a5f41b26f6f65a155078f0 (patch)
parent1ac7d194e5ca31d5284e410a87ad9f9669a7f5b5 (diff)
Avoid memory copy when verifying raidz/draid parity
Before this change for every valid parity column raidz_parity_verify() allocated new buffer and copied there existing data, then recalculated the parity and compared the result with the copy. This patch removes the memory copy, simply swapping original buffer pointers with newly allocated empty ones for parity recalculation and comparison. Original buffers with potentially incorrect parity data are then just freed, while new recalculated ones are used for repair. On a pool of 12 4-wide raidz vdevs, storing 1.5TB of 16MB blocks, this change reduces memory traffic during scrub by 17% and total unhalted CPU time by 25%. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored-By: iXsystems, Inc. Closes #13613
1 files changed, 3 insertions, 2 deletions
diff --git a/module/zfs/vdev_raidz.c b/module/zfs/vdev_raidz.c
index bc343c6254b7..3633937f462b 100644
--- a/module/zfs/vdev_raidz.c
+++ b/module/zfs/vdev_raidz.c
@@ -1815,8 +1815,9 @@ raidz_parity_verify(zio_t *zio, raidz_row_t *rr)
if (!rc->rc_tried || rc->rc_error != 0)
- orig[c] = abd_alloc_sametype(rc->rc_abd, rc->rc_size);
- abd_copy(orig[c], rc->rc_abd, rc->rc_size);
+ orig[c] = rc->rc_abd;
+ ASSERT3U(abd_get_size(rc->rc_abd), ==, rc->rc_size);
+ rc->rc_abd = abd_alloc_linear(rc->rc_size, B_FALSE);