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BRT: Skip getting length in brt_entry_lookup()

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Unlike DDT, where ZAP values may have different lengths due to
compression, all BRT entries are identical 8-byte counters.  It
does not make sense to first fetch the length only to assert it.
zap_lookup_uint64() is specifically designed to work with counters
of different size and should return error if something odd found.
Calling it straight allows to save some measurable CPU time.

Reviewed-by: Pawel Jakub Dawidek <pawel@dawidek.net>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15950
This commit is contained in:
Alexander Motin 2024-03-25 20:13:45 -04:00 committed by Brian Behlendorf
parent c94f730078
commit 3e91a9c525
1 changed files with 2 additions and 16 deletions
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18
module/zfs/brt.c
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@ -900,7 +900,6 @@ static int
brt_entry_lookup(brt_t *brt, brt_vdev_t *brtvd, brt_entry_t *bre)
{
uint64_t mos_entries;
uint64_t one, physsize;
int error;
ASSERT(RW_LOCK_HELD(&brt->brt_lock));
@ -918,21 +917,8 @@ brt_entry_lookup(brt_t *brt, brt_vdev_t *brtvd, brt_entry_t *bre)
brt_unlock(brt);
error = zap_length_uint64(brt->brt_mos, mos_entries, &bre->bre_offset,
BRT_KEY_WORDS, &one, &physsize);
if (error == 0) {
ASSERT3U(one, ==, 1);
ASSERT3U(physsize, ==, sizeof (bre->bre_refcount));
error = zap_lookup_uint64(brt->brt_mos, mos_entries,
&bre->bre_offset, BRT_KEY_WORDS, 1,
sizeof (bre->bre_refcount), &bre->bre_refcount);
BRT_DEBUG("ZAP lookup: object=%llu vdev=%llu offset=%llu "
"count=%llu error=%d", (u_longlong_t)mos_entries,
(u_longlong_t)brtvd->bv_vdevid,
(u_longlong_t)bre->bre_offset,
error == 0 ? (u_longlong_t)bre->bre_refcount : 0, error);
}
error = zap_lookup_uint64(brt->brt_mos, mos_entries, &bre->bre_offset,
BRT_KEY_WORDS, 1, sizeof (bre->bre_refcount), &bre->bre_refcount);
brt_wlock(brt);