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Limit dbuf cache sizes based only on ARC target size by default 

Set the initial max sizes to ULONG_MAX to allow the caches to grow
with the ARC.

Recalculate the metadata cache size on demand so it can adapt, too.

Update descriptions in zfs-module-parameters(5).

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matt Ahrens <matt@delphix.com>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #10563 
Closes #10610
This commit is contained in:
Ryan Moeller 2020-07-24 23:38:48 -04:00 committed by GitHub
parent 4fbdb10c7b
commit 8348fac30c
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 34 additions and 34 deletions
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22
man/man5/zfs-module-parameters.5
View File

@ -32,13 +32,12 @@ Description of the different parameters to the ZFS module.
\fBdbuf_cache_max_bytes\fR (ulong) \fBdbuf_cache_max_bytes\fR (ulong)
.ad .ad
.RS 12n .RS 12n
Maximum size in bytes of the dbuf cache. When \fB0\fR this value will default Maximum size in bytes of the dbuf cache. The target size is determined by the
to \fB1/2^dbuf_cache_shift\fR (1/32) of the target ARC size, otherwise the MIN versus \fB1/2^dbuf_cache_shift\fR (1/32) of the target ARC size. The
provided value in bytes will be used. The behavior of the dbuf cache and its behavior of the dbuf cache and its associated settings can be observed via the
associated settings can be observed via the \fB/proc/spl/kstat/zfs/dbufstats\fR \fB/proc/spl/kstat/zfs/dbufstats\fR kstat.
kstat.
.sp .sp
Default value: \fB0\fR. Default value: \fBULONG_MAX\fR.
.RE .RE
.sp .sp
@ -47,13 +46,12 @@ Default value: \fB0\fR.
\fBdbuf_metadata_cache_max_bytes\fR (ulong) \fBdbuf_metadata_cache_max_bytes\fR (ulong)
.ad .ad
.RS 12n .RS 12n
Maximum size in bytes of the metadata dbuf cache. When \fB0\fR this value will Maximum size in bytes of the metadata dbuf cache. The target size is
default to \fB1/2^dbuf_cache_shift\fR (1/16) of the target ARC size, otherwise determined by the MIN versus \fB1/2^dbuf_metadata_cache_shift\fR (1/64) of the
the provided value in bytes will be used. The behavior of the metadata dbuf target ARC size. The behavior of the metadata dbuf cache and its associated
cache and its associated settings can be observed via the settings can be observed via the \fB/proc/spl/kstat/zfs/dbufstats\fR kstat.
\fB/proc/spl/kstat/zfs/dbufstats\fR kstat.
.sp .sp
Default value: \fB0\fR. Default value: \fBULONG_MAX\fR.
.RE .RE
.sp .sp

46
module/zfs/dbuf.c
View File

@ -207,12 +207,16 @@ typedef struct dbuf_cache {
dbuf_cache_t dbuf_caches[DB_CACHE_MAX]; dbuf_cache_t dbuf_caches[DB_CACHE_MAX];
/* Size limits for the caches */ /* Size limits for the caches */
unsigned long dbuf_cache_max_bytes = 0; unsigned long dbuf_cache_max_bytes = ULONG_MAX;
unsigned long dbuf_metadata_cache_max_bytes = 0; unsigned long dbuf_metadata_cache_max_bytes = ULONG_MAX;
/* Set the default sizes of the caches to log2 fraction of arc size */ /* Set the default sizes of the caches to log2 fraction of arc size */
int dbuf_cache_shift = 5; int dbuf_cache_shift = 5;
int dbuf_metadata_cache_shift = 6; int dbuf_metadata_cache_shift = 6;
static unsigned long dbuf_cache_target_bytes(void);
static unsigned long dbuf_metadata_cache_target_bytes(void);
/* /*
* The LRU dbuf cache uses a three-stage eviction policy: * The LRU dbuf cache uses a three-stage eviction policy:
* - A low water marker designates when the dbuf eviction thread * - A low water marker designates when the dbuf eviction thread
@ -432,7 +436,7 @@ dbuf_include_in_metadata_cache(dmu_buf_impl_t *db)
*/ */
if (zfs_refcount_count( if (zfs_refcount_count(
&dbuf_caches[DB_DBUF_METADATA_CACHE].size) > &dbuf_caches[DB_DBUF_METADATA_CACHE].size) >
dbuf_metadata_cache_max_bytes) { dbuf_metadata_cache_target_bytes()) {
DBUF_STAT_BUMP(metadata_cache_overflow); DBUF_STAT_BUMP(metadata_cache_overflow);
return (B_FALSE); return (B_FALSE);
} }
@ -610,11 +614,26 @@ dbuf_cache_multilist_index_func(multilist_t *ml, void *obj)
multilist_get_num_sublists(ml)); multilist_get_num_sublists(ml));
} }
/*
* The target size of the dbuf cache can grow with the ARC target,
* unless limited by the tunable dbuf_cache_max_bytes.
*/
static inline unsigned long static inline unsigned long
dbuf_cache_target_bytes(void) dbuf_cache_target_bytes(void)
{ {
return MIN(dbuf_cache_max_bytes, return (MIN(dbuf_cache_max_bytes,
arc_target_bytes() >> dbuf_cache_shift); arc_target_bytes() >> dbuf_cache_shift));
}
/*
* The target size of the dbuf metadata cache can grow with the ARC target,
* unless limited by the tunable dbuf_metadata_cache_max_bytes.
*/
static inline unsigned long
dbuf_metadata_cache_target_bytes(void)
{
return (MIN(dbuf_metadata_cache_max_bytes,
arc_target_bytes() >> dbuf_metadata_cache_shift));
} }
static inline uint64_t static inline uint64_t
@ -805,23 +824,6 @@ retry:
dbuf_stats_init(h); dbuf_stats_init(h);
/*
* Setup the parameters for the dbuf caches. We set the sizes of the
* dbuf cache and the metadata cache to 1/32nd and 1/16th (default)
* of the target size of the ARC. If the values has been specified as
* a module option and they're not greater than the target size of the
* ARC, then we honor that value.
*/
if (dbuf_cache_max_bytes == 0 ||
dbuf_cache_max_bytes >= arc_target_bytes()) {
dbuf_cache_max_bytes = arc_target_bytes() >> dbuf_cache_shift;
}
if (dbuf_metadata_cache_max_bytes == 0 ||
dbuf_metadata_cache_max_bytes >= arc_target_bytes()) {
dbuf_metadata_cache_max_bytes =
arc_target_bytes() >> dbuf_metadata_cache_shift;
}
/* /*
* All entries are queued via taskq_dispatch_ent(), so min/maxalloc * All entries are queued via taskq_dispatch_ent(), so min/maxalloc
* configuration is not required. * configuration is not required.