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Reduce number of metaslab preload taskq threads. #15319

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Oct 6, 2023
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Reduce number of metaslab preload taskq threads. #15319

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1 change: 0 additions & 1 deletion include/sys/metaslab_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -250,7 +250,6 @@ struct metaslab_group {
int64_t mg_activation_count;
metaslab_class_t *mg_class;
vdev_t *mg_vd;
taskq_t *mg_taskq;
metaslab_group_t *mg_prev;
metaslab_group_t *mg_next;

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4 changes: 2 additions & 2 deletions include/sys/spa_impl.h
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Expand Up @@ -424,7 +424,9 @@ struct spa {

hrtime_t spa_ccw_fail_time; /* Conf cache write fail time */
taskq_t *spa_zvol_taskq; /* Taskq for minor management */
taskq_t *spa_metaslab_taskq; /* Taskq for metaslab preload */
taskq_t *spa_prefetch_taskq; /* Taskq for prefetch threads */
taskq_t *spa_upgrade_taskq; /* Taskq for upgrade jobs */
uint64_t spa_multihost; /* multihost aware (mmp) */
mmp_thread_t spa_mmp; /* multihost mmp thread */
list_t spa_leaf_list; /* list of leaf vdevs */
Expand All @@ -448,8 +450,6 @@ struct spa {
*/
spa_config_lock_t spa_config_lock[SCL_LOCKS]; /* config changes */
zfs_refcount_t spa_refcount; /* number of opens */

taskq_t *spa_upgrade_taskq; /* taskq for upgrade jobs */
};

extern char *spa_config_path;
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6 changes: 6 additions & 0 deletions man/man4/zfs.4
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Expand Up @@ -402,6 +402,12 @@ Practical upper limit of total metaslabs per top-level vdev.
.It Sy metaslab_preload_enabled Ns = Ns Sy 1 Ns | Ns 0 Pq int
Enable metaslab group preloading.
.
.It Sy metaslab_preload_limit Ns = Ns Sy 10 Pq uint
Maximum number of metaslabs per group to preload
.
.It Sy metaslab_preload_pct Ns = Ns Sy 50 Pq uint
Percentage of CPUs to run a metaslab preload taskq
.
.It Sy metaslab_lba_weighting_enabled Ns = Ns Sy 1 Ns | Ns 0 Pq int
Give more weight to metaslabs with lower LBAs,
assuming they have greater bandwidth,
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22 changes: 0 additions & 22 deletions module/os/freebsd/zfs/sysctl_os.c
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Expand Up @@ -614,28 +614,6 @@ SYSCTL_UINT(_vfs_zfs_metaslab, OID_AUTO, df_free_pct,
" space map to continue allocations in a first-fit fashion");
/* END CSTYLED */

/*
* Percentage of all cpus that can be used by the metaslab taskq.
*/
extern int metaslab_load_pct;

/* BEGIN CSTYLED */
SYSCTL_INT(_vfs_zfs_metaslab, OID_AUTO, load_pct,
CTLFLAG_RWTUN, &metaslab_load_pct, 0,
"Percentage of cpus that can be used by the metaslab taskq");
/* END CSTYLED */

/*
* Max number of metaslabs per group to preload.
*/
extern uint_t metaslab_preload_limit;

/* BEGIN CSTYLED */
SYSCTL_UINT(_vfs_zfs_metaslab, OID_AUTO, preload_limit,
CTLFLAG_RWTUN, &metaslab_preload_limit, 0,
"Max number of metaslabs per group to preload");
/* END CSTYLED */

/* mmp.c */

int
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23 changes: 8 additions & 15 deletions module/zfs/metaslab.c
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Expand Up @@ -205,11 +205,6 @@ static const uint32_t metaslab_min_search_count = 100;
*/
static int metaslab_df_use_largest_segment = B_FALSE;

/*
* Percentage of all cpus that can be used by the metaslab taskq.
*/
int metaslab_load_pct = 50;

/*
* These tunables control how long a metaslab will remain loaded after the
* last allocation from it. A metaslab can't be unloaded until at least
Expand Down Expand Up @@ -854,9 +849,6 @@ metaslab_group_create(metaslab_class_t *mc, vdev_t *vd, int allocators)
zfs_refcount_create_tracked(&mga->mga_alloc_queue_depth);
}

mg->mg_taskq = taskq_create("metaslab_group_taskq", metaslab_load_pct,
maxclsyspri, 10, INT_MAX, TASKQ_THREADS_CPU_PCT | TASKQ_DYNAMIC);

return (mg);
}

Expand All @@ -872,7 +864,6 @@ metaslab_group_destroy(metaslab_group_t *mg)
*/
ASSERT(mg->mg_activation_count <= 0);

taskq_destroy(mg->mg_taskq);
avl_destroy(&mg->mg_metaslab_tree);
mutex_destroy(&mg->mg_lock);
mutex_destroy(&mg->mg_ms_disabled_lock);
Expand Down Expand Up @@ -963,7 +954,7 @@ metaslab_group_passivate(metaslab_group_t *mg)
* allocations from taking place and any changes to the vdev tree.
*/
spa_config_exit(spa, locks & ~(SCL_ZIO - 1), spa);
taskq_wait_outstanding(mg->mg_taskq, 0);
taskq_wait_outstanding(spa->spa_metaslab_taskq, 0);
spa_config_enter(spa, locks & ~(SCL_ZIO - 1), spa, RW_WRITER);
metaslab_group_alloc_update(mg);
for (int i = 0; i < mg->mg_allocators; i++) {
Expand Down Expand Up @@ -3562,10 +3553,8 @@ metaslab_group_preload(metaslab_group_t *mg)
avl_tree_t *t = &mg->mg_metaslab_tree;
int m = 0;

if (spa_shutting_down(spa) || !metaslab_preload_enabled) {
taskq_wait_outstanding(mg->mg_taskq, 0);
if (spa_shutting_down(spa) || !metaslab_preload_enabled)
return;
}

mutex_enter(&mg->mg_lock);

Expand All @@ -3585,8 +3574,9 @@ metaslab_group_preload(metaslab_group_t *mg)
continue;
}

VERIFY(taskq_dispatch(mg->mg_taskq, metaslab_preload,
msp, TQ_SLEEP) != TASKQID_INVALID);
VERIFY(taskq_dispatch(spa->spa_metaslab_taskq, metaslab_preload,
msp, TQ_SLEEP | (m <= mg->mg_allocators ? TQ_FRONT : 0))
!= TASKQID_INVALID);
}
mutex_exit(&mg->mg_lock);
}
Expand Down Expand Up @@ -6215,6 +6205,9 @@ ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, debug_unload, INT, ZMOD_RW,
ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, preload_enabled, INT, ZMOD_RW,
"Preload potential metaslabs during reassessment");

ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, preload_limit, UINT, ZMOD_RW,
"Max number of metaslabs per group to preload");

ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, unload_delay, UINT, ZMOD_RW,
"Delay in txgs after metaslab was last used before unloading");

Expand Down
28 changes: 21 additions & 7 deletions module/zfs/spa.c
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Original file line number Diff line number Diff line change
Expand Up @@ -169,6 +169,11 @@ static int spa_load_impl(spa_t *spa, spa_import_type_t type,
const char **ereport);
static void spa_vdev_resilver_done(spa_t *spa);

/*
* Percentage of all CPUs that can be used by the metaslab preload taskq.
*/
static uint_t metaslab_preload_pct = 50;

static uint_t zio_taskq_batch_pct = 80; /* 1 thread per cpu in pset */
static uint_t zio_taskq_batch_tpq; /* threads per taskq */
static const boolean_t zio_taskq_sysdc = B_TRUE; /* use SDC scheduling class */
Expand Down Expand Up @@ -1399,6 +1404,13 @@ spa_activate(spa_t *spa, spa_mode_t mode)
spa->spa_zvol_taskq = taskq_create("z_zvol", 1, defclsyspri,
1, INT_MAX, 0);

/*
* The taskq to preload metaslabs.
*/
spa->spa_metaslab_taskq = taskq_create("z_metaslab",
metaslab_preload_pct, maxclsyspri, 1, INT_MAX,
TASKQ_DYNAMIC | TASKQ_THREADS_CPU_PCT);

/*
* Taskq dedicated to prefetcher threads: this is used to prevent the
* pool traverse code from monopolizing the global (and limited)
Expand Down Expand Up @@ -1434,6 +1446,11 @@ spa_deactivate(spa_t *spa)
spa->spa_zvol_taskq = NULL;
}

if (spa->spa_metaslab_taskq) {
taskq_destroy(spa->spa_metaslab_taskq);
spa->spa_metaslab_taskq = NULL;
}

if (spa->spa_prefetch_taskq) {
taskq_destroy(spa->spa_prefetch_taskq);
spa->spa_prefetch_taskq = NULL;
Expand Down Expand Up @@ -1706,13 +1723,7 @@ spa_unload(spa_t *spa)
* This ensures that there is no async metaslab prefetching
* while we attempt to unload the spa.
*/
if (spa->spa_root_vdev != NULL) {
for (int c = 0; c < spa->spa_root_vdev->vdev_children; c++) {
vdev_t *vc = spa->spa_root_vdev->vdev_child[c];
if (vc->vdev_mg != NULL)
taskq_wait(vc->vdev_mg->mg_taskq);
}
}
taskq_wait(spa->spa_metaslab_taskq);

if (spa->spa_mmp.mmp_thread)
mmp_thread_stop(spa);
Expand Down Expand Up @@ -10134,6 +10145,9 @@ EXPORT_SYMBOL(spa_prop_clear_bootfs);
/* asynchronous event notification */
EXPORT_SYMBOL(spa_event_notify);

ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, preload_pct, UINT, ZMOD_RW,
"Percentage of CPUs to run a metaslab preload taskq");

/* BEGIN CSTYLED */
ZFS_MODULE_PARAM(zfs_spa, spa_, load_verify_shift, UINT, ZMOD_RW,
"log2 fraction of arc that can be used by inflight I/Os when "
Expand Down