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Introduce a tunable to exclude special class buffers from L2ARC 

Special allocation class or dedup vdevs may have roughly the same
performance as L2ARC vdevs. Introduce a new tunable to exclude those
buffers from being cacheable on L2ARC.

Reviewed-by: Don Brady <don.brady@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes #11761
Closes #12285
This commit is contained in:
George Amanakis 2021-11-11 21:52:16 +01:00 committed by Tony Hutter
parent c8f795ba53
commit 8bd3dca9bf
8 changed files with 119 additions and 21 deletions
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1
include/sys/arc.h
View File

@ -85,6 +85,7 @@ typedef void arc_prune_func_t(int64_t bytes, void *priv);
/* Shared module parameters */
extern int zfs_arc_average_blocksize;
extern int l2arc_exclude_special;
/* generic arc_done_func_t's which you can use */
arc_read_done_func_t arc_bcopy_func;

11
include/sys/dbuf.h
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@ -441,16 +441,7 @@ dbuf_find_dirty_eq(dmu_buf_impl_t *db, uint64_t txg)
(dbuf_is_metadata(_db) && \
((_db)->db_objset->os_primary_cache == ZFS_CACHE_METADATA)))
#define DBUF_IS_L2CACHEABLE(_db) \
((_db)->db_objset->os_secondary_cache == ZFS_CACHE_ALL || \
(dbuf_is_metadata(_db) && \
((_db)->db_objset->os_secondary_cache == ZFS_CACHE_METADATA)))
#define DNODE_LEVEL_IS_L2CACHEABLE(_dn, _level) \
((_dn)->dn_objset->os_secondary_cache == ZFS_CACHE_ALL || \
(((_level) > 0 || \
DMU_OT_IS_METADATA((_dn)->dn_handle->dnh_dnode->dn_type)) && \
((_dn)->dn_objset->os_secondary_cache == ZFS_CACHE_METADATA)))
boolean_t dbuf_is_l2cacheable(dmu_buf_impl_t *db);
#ifdef ZFS_DEBUG

4
include/sys/dmu_objset.h
View File

@ -200,10 +200,6 @@ struct objset {
#define DMU_GROUPUSED_DNODE(os) ((os)->os_groupused_dnode.dnh_dnode)
#define DMU_PROJECTUSED_DNODE(os) ((os)->os_projectused_dnode.dnh_dnode)
#define DMU_OS_IS_L2CACHEABLE(os) \
((os)->os_secondary_cache == ZFS_CACHE_ALL || \
(os)->os_secondary_cache == ZFS_CACHE_METADATA)
/* called from zpl */
int dmu_objset_hold(const char *name, void *tag, objset_t **osp);
int dmu_objset_hold_flags(const char *name, boolean_t decrypt, void *tag,

5
man/man4/zfs.4
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@ -109,6 +109,11 @@ A value of
.Sy 100
disables this feature.
.
.It Sy l2arc_exclude_special Ns = Ns Sy 0 Ns | Ns 1 Pq int
Controls whether buffers present on special vdevs are eligibile for caching
into L2ARC.
If set to 1, exclude dbufs on special vdevs from being cached to L2ARC.
.
.It Sy l2arc_mfuonly Ns = Ns Sy 0 Ns | Ns 1 Pq int
Controls whether only MFU metadata and data are cached from ARC into L2ARC.
This may be desired to avoid wasting space on L2ARC when reading/writing large

12
module/zfs/arc.c
View File

@ -877,6 +877,14 @@ static void l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
#define l2arc_hdr_arcstats_decrement_state(hdr) \
l2arc_hdr_arcstats_update((hdr), B_FALSE, B_TRUE)
/*
* l2arc_exclude_special : A zfs module parameter that controls whether buffers
* present on special vdevs are eligibile for caching in L2ARC. If
* set to 1, exclude dbufs on special vdevs from being cached to
* L2ARC.
*/
int l2arc_exclude_special = 0;
/*
* l2arc_mfuonly : A ZFS module parameter that controls whether only MFU
* metadata and data are cached from ARC into L2ARC.
@ -11136,6 +11144,10 @@ ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, rebuild_blocks_min_l2size, ULONG, ZMOD_RW,
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, mfuonly, INT, ZMOD_RW,
"Cache only MFU data from ARC into L2ARC");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, exclude_special, INT, ZMOD_RW,
"If set to 1 exclude dbufs on special vdevs from being cached to "
"L2ARC.");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, lotsfree_percent, param_set_arc_int,
param_get_int, ZMOD_RW, "System free memory I/O throttle in bytes");

71
module/zfs/dbuf.c
View File

@ -53,6 +53,7 @@
#include <cityhash.h>
#include <sys/spa_impl.h>
#include <sys/wmsum.h>
#include <sys/vdev_impl.h>
kstat_t *dbuf_ksp;
@ -594,6 +595,68 @@ dbuf_is_metadata(dmu_buf_impl_t *db)
}
}
/*
* We want to exclude buffers that are on a special allocation class from
* L2ARC.
*/
boolean_t
dbuf_is_l2cacheable(dmu_buf_impl_t *db)
{
vdev_t *vd = NULL;
zfs_cache_type_t cache = db->db_objset->os_secondary_cache;
blkptr_t *bp = db->db_blkptr;
if (bp != NULL && !BP_IS_HOLE(bp)) {
uint64_t vdev = DVA_GET_VDEV(bp->blk_dva);
vdev_t *rvd = db->db_objset->os_spa->spa_root_vdev;
if (vdev < rvd->vdev_children)
vd = rvd->vdev_child[vdev];
if (cache == ZFS_CACHE_ALL ||
(dbuf_is_metadata(db) && cache == ZFS_CACHE_METADATA)) {
if (vd == NULL)
return (B_TRUE);
if ((vd->vdev_alloc_bias != VDEV_BIAS_SPECIAL &&
vd->vdev_alloc_bias != VDEV_BIAS_DEDUP) ||
l2arc_exclude_special == 0)
return (B_TRUE);
}
}
return (B_FALSE);
}
static inline boolean_t
dnode_level_is_l2cacheable(blkptr_t *bp, dnode_t *dn, int64_t level)
{
vdev_t *vd = NULL;
zfs_cache_type_t cache = dn->dn_objset->os_secondary_cache;
if (bp != NULL && !BP_IS_HOLE(bp)) {
uint64_t vdev = DVA_GET_VDEV(bp->blk_dva);
vdev_t *rvd = dn->dn_objset->os_spa->spa_root_vdev;
if (vdev < rvd->vdev_children)
vd = rvd->vdev_child[vdev];
if (cache == ZFS_CACHE_ALL || ((level > 0 ||
DMU_OT_IS_METADATA(dn->dn_handle->dnh_dnode->dn_type)) &&
cache == ZFS_CACHE_METADATA)) {
if (vd == NULL)
return (B_TRUE);
if ((vd->vdev_alloc_bias != VDEV_BIAS_SPECIAL &&
vd->vdev_alloc_bias != VDEV_BIAS_DEDUP) ||
l2arc_exclude_special == 0)
return (B_TRUE);
}
}
return (B_FALSE);
}
/*
* This function *must* return indices evenly distributed between all
@ -1523,7 +1586,7 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags,
DTRACE_SET_STATE(db, "read issued");
mutex_exit(&db->db_mtx);
if (DBUF_IS_L2CACHEABLE(db))
if (dbuf_is_l2cacheable(db))
aflags |= ARC_FLAG_L2CACHE;
dbuf_add_ref(db, NULL);
@ -3372,7 +3435,7 @@ dbuf_prefetch_impl(dnode_t *dn, int64_t level, uint64_t blkid,
dpa->dpa_arg = arg;
/* flag if L2ARC eligible, l2arc_noprefetch then decides */
if (DNODE_LEVEL_IS_L2CACHEABLE(dn, level))
if (dnode_level_is_l2cacheable(&bp, dn, level))
dpa->dpa_aflags |= ARC_FLAG_L2CACHE;
/*
@ -3390,7 +3453,7 @@ dbuf_prefetch_impl(dnode_t *dn, int64_t level, uint64_t blkid,
zbookmark_phys_t zb;
/* flag if L2ARC eligible, l2arc_noprefetch then decides */
if (DNODE_LEVEL_IS_L2CACHEABLE(dn, level))
if (dnode_level_is_l2cacheable(&bp, dn, level))
iter_aflags |= ARC_FLAG_L2CACHE;
SET_BOOKMARK(&zb, ds != NULL ? ds->ds_object : DMU_META_OBJSET,
@ -4989,7 +5052,7 @@ dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx)
children_ready_cb = dbuf_write_children_ready;
dr->dr_zio = arc_write(pio, os->os_spa, txg,
&dr->dr_bp_copy, data, DBUF_IS_L2CACHEABLE(db),
&dr->dr_bp_copy, data, dbuf_is_l2cacheable(db),
&zp, dbuf_write_ready,
children_ready_cb, dbuf_write_physdone,
dbuf_write_done, db, ZIO_PRIORITY_ASYNC_WRITE,

2
module/zfs/dmu.c
View File

@ -1846,7 +1846,7 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
dsa->dsa_tx = NULL;
zio_nowait(arc_write(pio, os->os_spa, txg,
zgd->zgd_bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
zgd->zgd_bp, dr->dt.dl.dr_data, dbuf_is_l2cacheable(db),
&zp, dmu_sync_ready, NULL, NULL, dmu_sync_done, dsa,
ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, &zb));

34
module/zfs/dmu_objset.c
View File

@ -63,6 +63,8 @@
#include <sys/dmu_recv.h>
#include <sys/zfs_project.h>
#include "zfs_namecheck.h"
#include <sys/vdev_impl.h>
#include <sys/arc.h>
/*
* Needed to close a window in dnode_move() that allows the objset to be freed
@ -411,6 +413,34 @@ dnode_multilist_index_func(multilist_t *ml, void *obj)
multilist_get_num_sublists(ml));
}
static inline boolean_t
dmu_os_is_l2cacheable(objset_t *os)
{
vdev_t *vd = NULL;
zfs_cache_type_t cache = os->os_secondary_cache;
blkptr_t *bp = os->os_rootbp;
if (bp != NULL && !BP_IS_HOLE(bp)) {
uint64_t vdev = DVA_GET_VDEV(bp->blk_dva);
vdev_t *rvd = os->os_spa->spa_root_vdev;
if (vdev < rvd->vdev_children)
vd = rvd->vdev_child[vdev];
if (cache == ZFS_CACHE_ALL || cache == ZFS_CACHE_METADATA) {
if (vd == NULL)
return (B_TRUE);
if ((vd->vdev_alloc_bias != VDEV_BIAS_SPECIAL &&
vd->vdev_alloc_bias != VDEV_BIAS_DEDUP) ||
l2arc_exclude_special == 0)
return (B_TRUE);
}
}
return (B_FALSE);
}
/*
* Instantiates the objset_t in-memory structure corresponding to the
* objset_phys_t that's pointed to by the specified blkptr_t.
@ -453,7 +483,7 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
if (DMU_OS_IS_L2CACHEABLE(os))
if (dmu_os_is_l2cacheable(os))
aflags |= ARC_FLAG_L2CACHE;
if (ds != NULL && ds->ds_dir->dd_crypto_obj != 0) {
@ -1661,7 +1691,7 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx)
}
zio = arc_write(pio, os->os_spa, tx->tx_txg,
blkptr_copy, os->os_phys_buf, DMU_OS_IS_L2CACHEABLE(os),
blkptr_copy, os->os_phys_buf, dmu_os_is_l2cacheable(os),
&zp, dmu_objset_write_ready, NULL, NULL, dmu_objset_write_done,
os, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);