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Do not request data L1 buffers on scan prefetch.

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Set ARC_FLAG_NO_BUF when prefetching data L1 buffers for scan.  We
do not prefetch data L0 buffers, so we do not need the L1 buffers,
only want them to be ready in ARC. This saves some CPU time on the
buffers decompression.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15029
This commit is contained in:
Alexander Motin 2023-07-20 12:10:04 -04:00 committed by Brian Behlendorf
parent 73ba5df31a
commit 83b0967c1f
1 changed files with 9 additions and 3 deletions
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12
module/zfs/dsl_scan.c
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@ -2080,10 +2080,16 @@ dsl_scan_prefetch_thread(void *arg)
zio_flags |= ZIO_FLAG_RAW;
}
/* We don't need data L1 buffer since we do not prefetch L0. */
blkptr_t *bp = &spic->spic_bp;
if (BP_GET_LEVEL(bp) == 1 && BP_GET_TYPE(bp) != DMU_OT_DNODE &&
BP_GET_TYPE(bp) != DMU_OT_OBJSET)
flags |= ARC_FLAG_NO_BUF;
/* issue the prefetch asynchronously */
(void) arc_read(scn->scn_zio_root, scn->scn_dp->dp_spa,
&spic->spic_bp, dsl_scan_prefetch_cb, spic->spic_spc,
ZIO_PRIORITY_SCRUB, zio_flags, &flags, &spic->spic_zb);
(void) arc_read(scn->scn_zio_root, spa, bp,
dsl_scan_prefetch_cb, spic->spic_spc, ZIO_PRIORITY_SCRUB,
zio_flags, &flags, &spic->spic_zb);
kmem_free(spic, sizeof (scan_prefetch_issue_ctx_t));
}