Switch refcount tracking from lists to AVL-trees.
With large number of tracked references list searches under the lock become too expensive, creating enormous lock contention. On my tests with ZFS_DEBUG enabled this increases write throughput with 32KB blocks from ~1.2GB/s to ~7.5GB/s. Reviewed-by: Brian Atkinson <batkinson@lanl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored by: iXsystems, Inc. Closes #14970
This commit is contained in:
Alexander Motin
GitHub
parent
8af1104f83
commit
d057807ede
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@ -27,6 +27,7 @@
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#define _SYS_ZFS_REFCOUNT_H
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#include <sys/inttypes.h>
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#include <sys/avl.h>
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#include <sys/list.h>
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#include <sys/zfs_context.h>
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@ -43,19 +44,22 @@ extern "C" {
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#ifdef ZFS_DEBUG
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typedef struct reference {
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list_node_t ref_link;
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union {
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avl_node_t a;
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list_node_t l;
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} ref_link;
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const void *ref_holder;
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uint64_t ref_number;
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uint8_t *ref_removed;
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boolean_t ref_search;
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} reference_t;
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typedef struct refcount {
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kmutex_t rc_mtx;
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boolean_t rc_tracked;
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list_t rc_list;
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list_t rc_removed;
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uint64_t rc_count;
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uint64_t rc_removed_count;
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kmutex_t rc_mtx;
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avl_tree_t rc_tree;
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list_t rc_removed;
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uint_t rc_removed_count;
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boolean_t rc_tracked;
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} zfs_refcount_t;
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/*
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@ -36,33 +36,40 @@ int reference_tracking_enable = B_FALSE;
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static uint_t reference_history = 3; /* tunable */
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static kmem_cache_t *reference_cache;
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static kmem_cache_t *reference_history_cache;
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void
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zfs_refcount_init(void)
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{
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reference_cache = kmem_cache_create("reference_cache",
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sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
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reference_history_cache = kmem_cache_create("reference_history_cache",
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sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
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}
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void
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zfs_refcount_fini(void)
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{
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kmem_cache_destroy(reference_cache);
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kmem_cache_destroy(reference_history_cache);
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}
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static int
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zfs_refcount_compare(const void *x1, const void *x2)
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{
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const reference_t *r1 = (const reference_t *)x1;
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const reference_t *r2 = (const reference_t *)x2;
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int cmp1 = TREE_CMP(r1->ref_holder, r2->ref_holder);
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int cmp2 = TREE_CMP(r1->ref_number, r2->ref_number);
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int cmp = cmp1 ? cmp1 : cmp2;
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return ((cmp || r1->ref_search) ? cmp : TREE_PCMP(r1, r2));
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}
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void
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zfs_refcount_create(zfs_refcount_t *rc)
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{
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mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
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list_create(&rc->rc_list, sizeof (reference_t),
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offsetof(reference_t, ref_link));
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avl_create(&rc->rc_tree, zfs_refcount_compare, sizeof (reference_t),
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offsetof(reference_t, ref_link.a));
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list_create(&rc->rc_removed, sizeof (reference_t),
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offsetof(reference_t, ref_link));
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offsetof(reference_t, ref_link.l));
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rc->rc_count = 0;
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rc->rc_removed_count = 0;
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rc->rc_tracked = reference_tracking_enable;
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@ -86,16 +93,15 @@ void
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zfs_refcount_destroy_many(zfs_refcount_t *rc, uint64_t number)
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{
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reference_t *ref;
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void *cookie = NULL;
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ASSERT3U(rc->rc_count, ==, number);
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while ((ref = list_remove_head(&rc->rc_list)))
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while ((ref = avl_destroy_nodes(&rc->rc_tree, &cookie)) != NULL)
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kmem_cache_free(reference_cache, ref);
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list_destroy(&rc->rc_list);
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avl_destroy(&rc->rc_tree);
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while ((ref = list_remove_head(&rc->rc_removed))) {
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kmem_cache_free(reference_history_cache, ref->ref_removed);
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while ((ref = list_remove_head(&rc->rc_removed)))
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kmem_cache_free(reference_cache, ref);
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}
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list_destroy(&rc->rc_removed);
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mutex_destroy(&rc->rc_mtx);
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}
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@ -121,10 +127,10 @@ zfs_refcount_count(zfs_refcount_t *rc)
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int64_t
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zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder)
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{
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reference_t *ref = NULL;
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reference_t *ref;
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int64_t count;
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if (!rc->rc_tracked) {
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if (likely(!rc->rc_tracked)) {
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count = atomic_add_64_nv(&(rc)->rc_count, number);
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ASSERT3U(count, >=, number);
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return (count);
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@ -133,8 +139,9 @@ zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder)
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ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
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ref->ref_holder = holder;
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ref->ref_number = number;
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ref->ref_search = B_FALSE;
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mutex_enter(&rc->rc_mtx);
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list_insert_head(&rc->rc_list, ref);
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avl_add(&rc->rc_tree, ref);
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rc->rc_count += number;
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count = rc->rc_count;
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mutex_exit(&rc->rc_mtx);
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@ -151,7 +158,7 @@ zfs_refcount_add(zfs_refcount_t *rc, const void *holder)
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void
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zfs_refcount_add_few(zfs_refcount_t *rc, uint64_t number, const void *holder)
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{
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if (!rc->rc_tracked)
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if (likely(!rc->rc_tracked))
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(void) zfs_refcount_add_many(rc, number, holder);
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else for (; number > 0; number--)
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(void) zfs_refcount_add(rc, holder);
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@ -161,34 +168,34 @@ int64_t
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zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number,
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const void *holder)
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{
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reference_t *ref;
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reference_t *ref, s;
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int64_t count;
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if (!rc->rc_tracked) {
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if (likely(!rc->rc_tracked)) {
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count = atomic_add_64_nv(&(rc)->rc_count, -number);
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ASSERT3S(count, >=, 0);
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return (count);
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}
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s.ref_holder = holder;
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s.ref_number = number;
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s.ref_search = B_TRUE;
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mutex_enter(&rc->rc_mtx);
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ASSERT3U(rc->rc_count, >=, number);
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for (ref = list_head(&rc->rc_list); ref;
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ref = list_next(&rc->rc_list, ref)) {
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if (ref->ref_holder == holder && ref->ref_number == number) {
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list_remove(&rc->rc_list, ref);
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ref = avl_find(&rc->rc_tree, &s, NULL);
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if (unlikely(ref == NULL)) {
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panic("No such hold %p on refcount %llx", holder,
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(u_longlong_t)(uintptr_t)rc);
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return (-1);
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}
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avl_remove(&rc->rc_tree, ref);
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if (reference_history > 0) {
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ref->ref_removed =
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kmem_cache_alloc(reference_history_cache,
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KM_SLEEP);
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list_insert_head(&rc->rc_removed, ref);
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rc->rc_removed_count++;
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if (rc->rc_removed_count > reference_history) {
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ref = list_tail(&rc->rc_removed);
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list_remove(&rc->rc_removed, ref);
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kmem_cache_free(reference_history_cache,
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ref->ref_removed);
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if (rc->rc_removed_count >= reference_history) {
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ref = list_remove_tail(&rc->rc_removed);
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kmem_cache_free(reference_cache, ref);
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rc->rc_removed_count--;
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} else {
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rc->rc_removed_count++;
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}
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} else {
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kmem_cache_free(reference_cache, ref);
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@ -197,11 +204,6 @@ zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number,
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count = rc->rc_count;
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mutex_exit(&rc->rc_mtx);
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return (count);
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}
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}
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panic("No such hold %p on refcount %llx", holder,
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(u_longlong_t)(uintptr_t)rc);
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return (-1);
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}
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int64_t
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@ -213,7 +215,7 @@ zfs_refcount_remove(zfs_refcount_t *rc, const void *holder)
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void
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zfs_refcount_remove_few(zfs_refcount_t *rc, uint64_t number, const void *holder)
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{
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if (!rc->rc_tracked)
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if (likely(!rc->rc_tracked))
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(void) zfs_refcount_remove_many(rc, number, holder);
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else for (; number > 0; number--)
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(void) zfs_refcount_remove(rc, holder);
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@ -222,31 +224,38 @@ zfs_refcount_remove_few(zfs_refcount_t *rc, uint64_t number, const void *holder)
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void
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zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src)
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{
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int64_t count, removed_count;
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list_t list, removed;
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avl_tree_t tree;
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list_t removed;
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reference_t *ref;
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void *cookie = NULL;
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uint64_t count;
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uint_t removed_count;
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list_create(&list, sizeof (reference_t),
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offsetof(reference_t, ref_link));
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avl_create(&tree, zfs_refcount_compare, sizeof (reference_t),
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offsetof(reference_t, ref_link.a));
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list_create(&removed, sizeof (reference_t),
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offsetof(reference_t, ref_link));
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offsetof(reference_t, ref_link.l));
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mutex_enter(&src->rc_mtx);
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count = src->rc_count;
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removed_count = src->rc_removed_count;
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src->rc_count = 0;
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src->rc_removed_count = 0;
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list_move_tail(&list, &src->rc_list);
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avl_swap(&tree, &src->rc_tree);
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list_move_tail(&removed, &src->rc_removed);
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mutex_exit(&src->rc_mtx);
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mutex_enter(&dst->rc_mtx);
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dst->rc_count += count;
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dst->rc_removed_count += removed_count;
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list_move_tail(&dst->rc_list, &list);
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if (avl_is_empty(&dst->rc_tree))
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avl_swap(&dst->rc_tree, &tree);
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else while ((ref = avl_destroy_nodes(&tree, &cookie)) != NULL)
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avl_add(&dst->rc_tree, ref);
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list_move_tail(&dst->rc_removed, &removed);
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mutex_exit(&dst->rc_mtx);
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list_destroy(&list);
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avl_destroy(&tree);
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list_destroy(&removed);
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}
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@ -254,23 +263,19 @@ void
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zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number,
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const void *current_holder, const void *new_holder)
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{
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reference_t *ref;
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boolean_t found = B_FALSE;
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reference_t *ref, s;
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if (!rc->rc_tracked)
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if (likely(!rc->rc_tracked))
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return;
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s.ref_holder = current_holder;
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s.ref_number = number;
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s.ref_search = B_TRUE;
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mutex_enter(&rc->rc_mtx);
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for (ref = list_head(&rc->rc_list); ref;
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ref = list_next(&rc->rc_list, ref)) {
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if (ref->ref_holder == current_holder &&
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ref->ref_number == number) {
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ref = avl_find(&rc->rc_tree, &s, NULL);
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ASSERT(ref);
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ref->ref_holder = new_holder;
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found = B_TRUE;
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break;
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}
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}
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ASSERT(found);
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avl_update(&rc->rc_tree, ref);
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mutex_exit(&rc->rc_mtx);
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}
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@ -290,21 +295,23 @@ zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder,
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boolean_t
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zfs_refcount_held(zfs_refcount_t *rc, const void *holder)
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{
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reference_t *ref;
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reference_t *ref, s;
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avl_index_t idx;
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boolean_t res;
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if (!rc->rc_tracked)
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if (likely(!rc->rc_tracked))
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return (zfs_refcount_count(rc) > 0);
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s.ref_holder = holder;
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s.ref_number = 0;
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s.ref_search = B_TRUE;
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mutex_enter(&rc->rc_mtx);
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for (ref = list_head(&rc->rc_list); ref;
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ref = list_next(&rc->rc_list, ref)) {
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if (ref->ref_holder == holder) {
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ref = avl_find(&rc->rc_tree, &s, &idx);
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if (likely(ref == NULL))
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ref = avl_nearest(&rc->rc_tree, idx, AVL_AFTER);
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res = ref && ref->ref_holder == holder;
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mutex_exit(&rc->rc_mtx);
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return (B_TRUE);
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}
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}
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mutex_exit(&rc->rc_mtx);
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return (B_FALSE);
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return (res);
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}
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/*
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@ -315,21 +322,23 @@ zfs_refcount_held(zfs_refcount_t *rc, const void *holder)
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boolean_t
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zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder)
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{
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reference_t *ref;
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reference_t *ref, s;
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avl_index_t idx;
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boolean_t res;
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if (!rc->rc_tracked)
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if (likely(!rc->rc_tracked))
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return (B_TRUE);
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mutex_enter(&rc->rc_mtx);
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for (ref = list_head(&rc->rc_list); ref;
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ref = list_next(&rc->rc_list, ref)) {
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if (ref->ref_holder == holder) {
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s.ref_holder = holder;
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s.ref_number = 0;
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s.ref_search = B_TRUE;
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ref = avl_find(&rc->rc_tree, &s, &idx);
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if (likely(ref == NULL))
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ref = avl_nearest(&rc->rc_tree, idx, AVL_AFTER);
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res = ref == NULL || ref->ref_holder != holder;
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mutex_exit(&rc->rc_mtx);
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return (B_FALSE);
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}
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}
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mutex_exit(&rc->rc_mtx);
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return (B_TRUE);
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return (res);
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}
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EXPORT_SYMBOL(zfs_refcount_create);
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