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Introduce zfs_refcount_(add|remove)_few().

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There are two places where we need to add/remove several references
with semantics of zfs_refcount_(add|remove). But when debug/tracing
is disabled, it is a crime to run multiple atomic_inc() in a loop,
especially under congested pool-wide allocator lock.

Introduced new functions implement the same semantics as the loop,
but without overhead in production builds.

Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #14934
This commit is contained in:
Alexander Motin
2023-06-05 14:51:44 -04:00
committed by GitHub
parent dae3c549f5
commit 5ba4025a8d
4 changed files with 30 additions and 9 deletions
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include/sys/zfs_refcount.h
+9 -3
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@@ -73,13 +73,15 @@ int64_t zfs_refcount_count(zfs_refcount_t *);
int64_t zfs_refcount_add(zfs_refcount_t *, const void *);
int64_t zfs_refcount_remove(zfs_refcount_t *, const void *);
/*
* Note that (add|remove)_many add/remove one reference with "number" N,
* _not_ make N references with "number" 1, which is what vanilla
* zfs_refcount_(add|remove) would do if called N times.
* Note that (add|remove)_many adds/removes one reference with "number" N,
* _not_ N references with "number" 1, which is what (add|remove)_few does,
* or what vanilla zfs_refcount_(add|remove) called N times would do.
*
* Attempting to remove a reference with number N when none exists is a
* panic on debug kernels with reference_tracking enabled.
*/
void zfs_refcount_add_few(zfs_refcount_t *, uint64_t, const void *);
void zfs_refcount_remove_few(zfs_refcount_t *, uint64_t, const void *);
int64_t zfs_refcount_add_many(zfs_refcount_t *, uint64_t, const void *);
int64_t zfs_refcount_remove_many(zfs_refcount_t *, uint64_t, const void *);
void zfs_refcount_transfer(zfs_refcount_t *, zfs_refcount_t *);
@@ -108,6 +110,10 @@ typedef struct refcount {
#define zfs_refcount_count(rc) atomic_load_64(&(rc)->rc_count)
#define zfs_refcount_add(rc, holder) atomic_inc_64_nv(&(rc)->rc_count)
#define zfs_refcount_remove(rc, holder) atomic_dec_64_nv(&(rc)->rc_count)
#define zfs_refcount_add_few(rc, number, holder) \
atomic_add_64(&(rc)->rc_count, number)
#define zfs_refcount_remove_few(rc, number, holder) \
atomic_add_64(&(rc)->rc_count, -number)
#define zfs_refcount_add_many(rc, number, holder) \
atomic_add_64_nv(&(rc)->rc_count, number)
#define zfs_refcount_remove_many(rc, number, holder) \