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ARC: Remove b_cv from struct l1arc_buf_hdr 

Earlier as part of #14123 I've removed one use of b_cv.  This patch
reuses the same approach to remove the other one from much more
rare code path.

This saves 16 bytes of L1 ARC header on FreeBSD (reducing it from
200 to 184 bytes) and seems even more on Linux.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15340
This commit is contained in:
Alexander Motin 2023-10-04 17:45:00 -04:00 committed by GitHub
parent f795e90a11
commit 2a6c62109c
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 22 additions and 14 deletions
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2
include/sys/arc_impl.h
View File

@ -159,8 +159,6 @@ struct arc_write_callback {
* these two allocation states.
*/
typedef struct l1arc_buf_hdr {
/* for waiting on reads to complete */
kcondvar_t b_cv;
uint8_t b_byteswap;
/* protected by arc state mutex */

34
module/zfs/arc.c
View File

@ -1151,7 +1151,6 @@ hdr_full_cons(void *vbuf, void *unused, int kmflag)
memset(hdr, 0, HDR_FULL_SIZE);
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
zfs_refcount_create(&hdr->b_l1hdr.b_refcnt);
#ifdef ZFS_DEBUG
mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
@ -1211,7 +1210,6 @@ hdr_full_dest(void *vbuf, void *unused)
arc_buf_hdr_t *hdr = vbuf;
ASSERT(HDR_EMPTY(hdr));
cv_destroy(&hdr->b_l1hdr.b_cv);
zfs_refcount_destroy(&hdr->b_l1hdr.b_refcnt);
#ifdef ZFS_DEBUG
mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
@ -5586,13 +5584,6 @@ arc_read_done(zio_t *zio)
buf_hash_remove(hdr);
}
/*
* Broadcast before we drop the hash_lock to avoid the possibility
* that the hdr (and hence the cv) might be freed before we get to
* the cv_broadcast().
*/
cv_broadcast(&hdr->b_l1hdr.b_cv);
arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
(void) remove_reference(hdr, hdr);
@ -5787,8 +5778,7 @@ top:
}
acb->acb_zio_head = head_zio;
acb->acb_next = hdr->b_l1hdr.b_acb;
if (hdr->b_l1hdr.b_acb)
hdr->b_l1hdr.b_acb->acb_prev = acb;
hdr->b_l1hdr.b_acb->acb_prev = acb;
hdr->b_l1hdr.b_acb = acb;
}
mutex_exit(hash_lock);
@ -5928,8 +5918,28 @@ top:
* and so the performance impact shouldn't
* matter.
*/
cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
arc_callback_t *acb = kmem_zalloc(
sizeof (arc_callback_t), KM_SLEEP);
acb->acb_wait = B_TRUE;
mutex_init(&acb->acb_wait_lock, NULL,
MUTEX_DEFAULT, NULL);
cv_init(&acb->acb_wait_cv, NULL, CV_DEFAULT,
NULL);
acb->acb_zio_head =
hdr->b_l1hdr.b_acb->acb_zio_head;
acb->acb_next = hdr->b_l1hdr.b_acb;
hdr->b_l1hdr.b_acb->acb_prev = acb;
hdr->b_l1hdr.b_acb = acb;
mutex_exit(hash_lock);
mutex_enter(&acb->acb_wait_lock);
while (acb->acb_wait) {
cv_wait(&acb->acb_wait_cv,
&acb->acb_wait_lock);
}
mutex_exit(&acb->acb_wait_lock);
mutex_destroy(&acb->acb_wait_lock);
cv_destroy(&acb->acb_wait_cv);
kmem_free(acb, sizeof (arc_callback_t));
goto top;
}
}