From 462217d1c24a0769ec32b6f6e378868c311b2448 Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Wed, 22 Dec 2021 20:07:13 -0500 Subject: [PATCH] Reduce number of arc_prune threads MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On FreeBSD vnode reclamation is single-threaded, protected by single global lock. Linux seems to be able to use a thread per mount point, but at this time it creates more harm than good. Reduce number of threads to 1, adding tunable in case somebody wants to try more. Reviewed-by: Ryan Moeller Reviewed-by: Brian Behlendorf Reviewed-by: Chris Dunlop Reviewed-by: Ahelenia Ziemiańska Signed-off-by: Alexander Motin Closes #12896 Issue #9966 --- man/man4/zfs.4 | 7 +++++++ module/zfs/arc.c | 13 ++++++++++--- 2 files changed, 17 insertions(+), 3 deletions(-) diff --git a/man/man4/zfs.4 b/man/man4/zfs.4 index ae10b2a37d..7b5907e93d 100644 --- a/man/man4/zfs.4 +++ b/man/man4/zfs.4 @@ -676,6 +676,13 @@ Minimum time "prescient prefetched" blocks are locked in the ARC. These blocks are meant to be prefetched fairly aggressively ahead of the code that may use them. . +.It Sy zfs_arc_prune_task_threads Ns = Ns Sy 1 Pq int +Number of arc_prune threads. +.Fx +does not need more than one. +Linux may theoretically use one per mount point up to number of CPUs, +but that was not proven to be useful. +. .It Sy zfs_max_missing_tvds Ns = Ns Sy 0 Pq int Number of missing top-level vdevs which will be allowed during pool import (only in read-only mode). diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 5427f2a71a..abd5ba50c7 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -463,6 +463,11 @@ int zfs_arc_meta_strategy = ARC_STRATEGY_META_BALANCED; int zfs_arc_meta_adjust_restarts = 4096; int zfs_arc_lotsfree_percent = 10; +/* + * Number of arc_prune threads + */ +static int zfs_arc_prune_task_threads = 1; + /* The 6 states: */ arc_state_t ARC_anon; arc_state_t ARC_mru; @@ -7983,9 +7988,8 @@ arc_init(void) offsetof(arc_prune_t, p_node)); mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL); - arc_prune_taskq = taskq_create("arc_prune", 100, defclsyspri, - boot_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC | - TASKQ_THREADS_CPU_PCT); + arc_prune_taskq = taskq_create("arc_prune", zfs_arc_prune_task_threads, + defclsyspri, 100, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC); arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); @@ -11132,4 +11136,7 @@ ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, eviction_pct, INT, ZMOD_RW, ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, evict_batch_limit, INT, ZMOD_RW, "The number of headers to evict per sublist before moving to the next"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, prune_task_threads, INT, ZMOD_RW, + "Number of arc_prune threads"); /* END CSTYLED */