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Add prefetch property 

ZFS prefetch is currently governed by the zfs_prefetch_disable
tunable. However, this is a module-wide settings - if a specific
dataset benefits from prefetch, while others have issue with it,
an optimal solution does not exists.

This commit introduce the "prefetch" tri-state property, which enable
granular control (at dataset/volume level) for prefetching.

This patch does not remove the zfs_prefetch_disable, which remains
a system-wide switch for enable/disable prefetch. However, to avoid
duplication, it would be preferable to deprecate and then remove
the module tunable.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Signed-off-by: Gionatan Danti <g.danti@assyoma.it>
Co-authored-by: Gionatan Danti <g.danti@assyoma.it>
Closes #15237 
Closes #15436
This commit is contained in:
Brian Behlendorf 2023-10-24 11:00:07 -07:00 committed by Tony Hutter
parent 706307445e
commit 61f3638a34
7 changed files with 63 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/sys/dmu_objset.h
View File

@ -132,6 +132,7 @@ struct objset {
zfs_logbias_op_t os_logbias;
zfs_cache_type_t os_primary_cache;
zfs_cache_type_t os_secondary_cache;
zfs_prefetch_type_t os_prefetch;
zfs_sync_type_t os_sync;
zfs_redundant_metadata_type_t os_redundant_metadata;
uint64_t os_recordsize;

7
include/sys/fs/zfs.h
View File

@ -191,6 +191,7 @@ typedef enum {
ZFS_PROP_REDACTED,
ZFS_PROP_REDACT_SNAPS,
ZFS_PROP_SNAPSHOTS_CHANGED,
ZFS_PROP_PREFETCH,
ZFS_NUM_PROPS
} zfs_prop_t;
@ -546,6 +547,12 @@ typedef enum zfs_key_location {
ZFS_KEYLOCATION_LOCATIONS
} zfs_keylocation_t;
typedef enum {
ZFS_PREFETCH_NONE = 0,
ZFS_PREFETCH_METADATA = 1,
ZFS_PREFETCH_ALL = 2
} zfs_prefetch_type_t;
#define DEFAULT_PBKDF2_ITERATIONS 350000
#define MIN_PBKDF2_ITERATIONS 100000

3
lib/libzfs/libzfs.abi
View File

@ -1867,7 +1867,8 @@
<enumerator name='ZFS_PROP_REDACTED' value='93'/>
<enumerator name='ZFS_PROP_REDACT_SNAPS' value='94'/>
<enumerator name='ZFS_PROP_SNAPSHOTS_CHANGED' value='95'/>
<enumerator name='ZFS_NUM_PROPS' value='96'/>
<enumerator name='ZFS_PROP_PREFETCH' value='96'/>
<enumerator name='ZFS_NUM_PROPS' value='97'/>
</enum-decl>
<typedef-decl name='zfs_prop_t' type-id='4b000d60' id='58603c44'/>
<enum-decl name='zprop_source_t' naming-typedef-id='a2256d42' id='5903f80e'>

17
man/man7/zfsprops.7
View File

@ -1613,6 +1613,23 @@ If this property is set to
then only metadata is cached.
The default value is
.Sy all .
.It Sy prefetch Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata
Controls what speculative prefetch does.
If this property is set to
.Sy all ,
then both user data and metadata are prefetched.
If this property is set to
.Sy none ,
then neither user data nor metadata are prefetched.
If this property is set to
.Sy metadata ,
then only metadata are prefetched.
The default value is
.Sy all .
.Pp
Please note that the module parameter zfs_disable_prefetch=1 can
be used to totally disable speculative prefetch, bypassing anything
this property does.
.It Sy setuid Ns = Ns Sy on Ns | Ns Sy off
Controls whether the setuid bit is respected for the file system.
The default value is

11
module/zcommon/zfs_prop.c
View File

@ -345,6 +345,13 @@ zfs_prop_init(void)
{ NULL }
};
static const zprop_index_t prefetch_table[] = {
{ "none", ZFS_PREFETCH_NONE },
{ "metadata", ZFS_PREFETCH_METADATA },
{ "all", ZFS_PREFETCH_ALL },
{ NULL }
};
static const zprop_index_t sync_table[] = {
{ "standard", ZFS_SYNC_STANDARD },
{ "always", ZFS_SYNC_ALWAYS },
@ -453,6 +460,10 @@ zfs_prop_init(void)
ZFS_CACHE_ALL, PROP_INHERIT,
ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT | ZFS_TYPE_VOLUME,
"all | none | metadata", "SECONDARYCACHE", cache_table, sfeatures);
zprop_register_index(ZFS_PROP_PREFETCH, "prefetch",
ZFS_PREFETCH_ALL, PROP_INHERIT,
ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT | ZFS_TYPE_VOLUME,
"none | metadata | all", "PREFETCH", prefetch_table, sfeatures);
zprop_register_index(ZFS_PROP_LOGBIAS, "logbias", ZFS_LOGBIAS_LATENCY,
PROP_INHERIT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
"latency | throughput", "LOGBIAS", logbias_table, sfeatures);

19
module/zfs/dmu_objset.c
View File

@ -263,6 +263,19 @@ secondary_cache_changed_cb(void *arg, uint64_t newval)
os->os_secondary_cache = newval;
}
static void
prefetch_changed_cb(void *arg, uint64_t newval)
{
objset_t *os = arg;
/*
* Inheritance should have been done by now.
*/
ASSERT(newval == ZFS_PREFETCH_ALL || newval == ZFS_PREFETCH_NONE ||
newval == ZFS_PREFETCH_METADATA);
os->os_prefetch = newval;
}
static void
sync_changed_cb(void *arg, uint64_t newval)
{
@ -562,6 +575,11 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
zfs_prop_to_name(ZFS_PROP_SECONDARYCACHE),
secondary_cache_changed_cb, os);
}
if (err == 0) {
err = dsl_prop_register(ds,
zfs_prop_to_name(ZFS_PROP_PREFETCH),
prefetch_changed_cb, os);
}
if (!ds->ds_is_snapshot) {
if (err == 0) {
err = dsl_prop_register(ds,
@ -635,6 +653,7 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
os->os_primary_cache = ZFS_CACHE_ALL;
os->os_secondary_cache = ZFS_CACHE_ALL;
os->os_dnodesize = DNODE_MIN_SIZE;
os->os_prefetch = ZFS_PREFETCH_ALL;
}
if (ds == NULL || !ds->ds_is_snapshot)

7
module/zfs/dmu_zfetch.c
View File

@ -471,9 +471,14 @@ dmu_zfetch_prepare(zfetch_t *zf, uint64_t blkid, uint64_t nblks,
{
zstream_t *zs;
spa_t *spa = zf->zf_dnode->dn_objset->os_spa;
zfs_prefetch_type_t os_prefetch = zf->zf_dnode->dn_objset->os_prefetch;
if (zfs_prefetch_disable)
if (zfs_prefetch_disable || os_prefetch == ZFS_PREFETCH_NONE)
return (NULL);
if (os_prefetch == ZFS_PREFETCH_METADATA)
fetch_data = B_FALSE;
/*
* If we haven't yet loaded the indirect vdevs' mappings, we
* can only read from blocks that we carefully ensure are on