Reduce dirty records memory usage

[zfs.git] / module / zfs / refcount.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or https://opensource.org/licenses/CDDL-1.0.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2021 by Delphix. All rights reserved.
 */

#include <sys/zfs_context.h>
#include <sys/zfs_refcount.h>

#ifdef  ZFS_DEBUG
/*
 * Reference count tracking is disabled by default.  It's memory requirements
 * are reasonable, however as implemented it consumes a significant amount of
 * cpu time.  Until its performance is improved it should be manually enabled.
 */
int reference_tracking_enable = B_FALSE;
static uint_t reference_history = 3; /* tunable */

static kmem_cache_t *reference_cache;

void
zfs_refcount_init(void)
{
        reference_cache = kmem_cache_create("reference_cache",
            sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
}

void
zfs_refcount_fini(void)
{
        kmem_cache_destroy(reference_cache);
}

static int
zfs_refcount_compare(const void *x1, const void *x2)
{
        const reference_t *r1 = (const reference_t *)x1;
        const reference_t *r2 = (const reference_t *)x2;

        int cmp1 = TREE_CMP(r1->ref_holder, r2->ref_holder);
        int cmp2 = TREE_CMP(r1->ref_number, r2->ref_number);
        int cmp = cmp1 ? cmp1 : cmp2;
        return ((cmp || r1->ref_search) ? cmp : TREE_PCMP(r1, r2));
}

void
zfs_refcount_create(zfs_refcount_t *rc)
{
        mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
        avl_create(&rc->rc_tree, zfs_refcount_compare, sizeof (reference_t),
            offsetof(reference_t, ref_link.a));
        list_create(&rc->rc_removed, sizeof (reference_t),
            offsetof(reference_t, ref_link.l));
        rc->rc_count = 0;
        rc->rc_removed_count = 0;
        rc->rc_tracked = reference_tracking_enable;
}

void
zfs_refcount_create_tracked(zfs_refcount_t *rc)
{
        zfs_refcount_create(rc);
        rc->rc_tracked = B_TRUE;
}

void
zfs_refcount_create_untracked(zfs_refcount_t *rc)
{
        zfs_refcount_create(rc);
        rc->rc_tracked = B_FALSE;
}

void
zfs_refcount_destroy_many(zfs_refcount_t *rc, uint64_t number)
{
        reference_t *ref;
        void *cookie = NULL;

        ASSERT3U(rc->rc_count, ==, number);
        while ((ref = avl_destroy_nodes(&rc->rc_tree, &cookie)) != NULL)
                kmem_cache_free(reference_cache, ref);
        avl_destroy(&rc->rc_tree);

        while ((ref = list_remove_head(&rc->rc_removed)))
                kmem_cache_free(reference_cache, ref);
        list_destroy(&rc->rc_removed);
        mutex_destroy(&rc->rc_mtx);
}

void
zfs_refcount_destroy(zfs_refcount_t *rc)
{
        zfs_refcount_destroy_many(rc, 0);
}

int
zfs_refcount_is_zero(zfs_refcount_t *rc)
{
        return (zfs_refcount_count(rc) == 0);
}

int64_t
zfs_refcount_count(zfs_refcount_t *rc)
{
        return (atomic_load_64(&rc->rc_count));
}

int64_t
zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder)
{
        reference_t *ref;
        int64_t count;

        if (likely(!rc->rc_tracked)) {
                count = atomic_add_64_nv(&(rc)->rc_count, number);
                ASSERT3U(count, >=, number);
                return (count);
        }

        ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
        ref->ref_holder = holder;
        ref->ref_number = number;
        ref->ref_search = B_FALSE;
        mutex_enter(&rc->rc_mtx);
        avl_add(&rc->rc_tree, ref);
        rc->rc_count += number;
        count = rc->rc_count;
        mutex_exit(&rc->rc_mtx);

        return (count);
}

int64_t
zfs_refcount_add(zfs_refcount_t *rc, const void *holder)
{
        return (zfs_refcount_add_many(rc, 1, holder));
}

void
zfs_refcount_add_few(zfs_refcount_t *rc, uint64_t number, const void *holder)
{
        if (likely(!rc->rc_tracked))
                (void) zfs_refcount_add_many(rc, number, holder);
        else for (; number > 0; number--)
                (void) zfs_refcount_add(rc, holder);
}

int64_t
zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number,
    const void *holder)
{
        reference_t *ref, s;
        int64_t count;

        if (likely(!rc->rc_tracked)) {
                count = atomic_add_64_nv(&(rc)->rc_count, -number);
                ASSERT3S(count, >=, 0);
                return (count);
        }

        s.ref_holder = holder;
        s.ref_number = number;
        s.ref_search = B_TRUE;
        mutex_enter(&rc->rc_mtx);
        ASSERT3U(rc->rc_count, >=, number);
        ref = avl_find(&rc->rc_tree, &s, NULL);
        if (unlikely(ref == NULL)) {
                panic("No such hold %p on refcount %llx", holder,
                    (u_longlong_t)(uintptr_t)rc);
                return (-1);
        }
        avl_remove(&rc->rc_tree, ref);
        if (reference_history > 0) {
                list_insert_head(&rc->rc_removed, ref);
                if (rc->rc_removed_count >= reference_history) {
                        ref = list_remove_tail(&rc->rc_removed);
                        kmem_cache_free(reference_cache, ref);
                } else {
                        rc->rc_removed_count++;
                }
        } else {
                kmem_cache_free(reference_cache, ref);
        }
        rc->rc_count -= number;
        count = rc->rc_count;
        mutex_exit(&rc->rc_mtx);
        return (count);
}

int64_t
zfs_refcount_remove(zfs_refcount_t *rc, const void *holder)
{
        return (zfs_refcount_remove_many(rc, 1, holder));
}

void
zfs_refcount_remove_few(zfs_refcount_t *rc, uint64_t number, const void *holder)
{
        if (likely(!rc->rc_tracked))
                (void) zfs_refcount_remove_many(rc, number, holder);
        else for (; number > 0; number--)
                (void) zfs_refcount_remove(rc, holder);
}

void
zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src)
{
        avl_tree_t tree;
        list_t removed;
        reference_t *ref;
        void *cookie = NULL;
        uint64_t count;
        uint_t removed_count;

        avl_create(&tree, zfs_refcount_compare, sizeof (reference_t),
            offsetof(reference_t, ref_link.a));
        list_create(&removed, sizeof (reference_t),
            offsetof(reference_t, ref_link.l));

        mutex_enter(&src->rc_mtx);
        count = src->rc_count;
        removed_count = src->rc_removed_count;
        src->rc_count = 0;
        src->rc_removed_count = 0;
        avl_swap(&tree, &src->rc_tree);
        list_move_tail(&removed, &src->rc_removed);
        mutex_exit(&src->rc_mtx);

        mutex_enter(&dst->rc_mtx);
        dst->rc_count += count;
        dst->rc_removed_count += removed_count;
        if (avl_is_empty(&dst->rc_tree))
                avl_swap(&dst->rc_tree, &tree);
        else while ((ref = avl_destroy_nodes(&tree, &cookie)) != NULL)
                avl_add(&dst->rc_tree, ref);
        list_move_tail(&dst->rc_removed, &removed);
        mutex_exit(&dst->rc_mtx);

        avl_destroy(&tree);
        list_destroy(&removed);
}

void
zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number,
    const void *current_holder, const void *new_holder)
{
        reference_t *ref, s;

        if (likely(!rc->rc_tracked))
                return;

        s.ref_holder = current_holder;
        s.ref_number = number;
        s.ref_search = B_TRUE;
        mutex_enter(&rc->rc_mtx);
        ref = avl_find(&rc->rc_tree, &s, NULL);
        ASSERT(ref);
        ref->ref_holder = new_holder;
        avl_update(&rc->rc_tree, ref);
        mutex_exit(&rc->rc_mtx);
}

void
zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder,
    const void *new_holder)
{
        return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder,
            new_holder));
}

/*
 * If tracking is enabled, return true if a reference exists that matches
 * the "holder" tag. If tracking is disabled, then return true if a reference
 * might be held.
 */
boolean_t
zfs_refcount_held(zfs_refcount_t *rc, const void *holder)
{
        reference_t *ref, s;
        avl_index_t idx;
        boolean_t res;

        if (likely(!rc->rc_tracked))
                return (zfs_refcount_count(rc) > 0);

        s.ref_holder = holder;
        s.ref_number = 0;
        s.ref_search = B_TRUE;
        mutex_enter(&rc->rc_mtx);
        ref = avl_find(&rc->rc_tree, &s, &idx);
        if (likely(ref == NULL))
                ref = avl_nearest(&rc->rc_tree, idx, AVL_AFTER);
        res = ref && ref->ref_holder == holder;
        mutex_exit(&rc->rc_mtx);
        return (res);
}

/*
 * If tracking is enabled, return true if a reference does not exist that
 * matches the "holder" tag. If tracking is disabled, always return true
 * since the reference might not be held.
 */
boolean_t
zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder)
{
        reference_t *ref, s;
        avl_index_t idx;
        boolean_t res;

        if (likely(!rc->rc_tracked))
                return (B_TRUE);

        mutex_enter(&rc->rc_mtx);
        s.ref_holder = holder;
        s.ref_number = 0;
        s.ref_search = B_TRUE;
        ref = avl_find(&rc->rc_tree, &s, &idx);
        if (likely(ref == NULL))
                ref = avl_nearest(&rc->rc_tree, idx, AVL_AFTER);
        res = ref == NULL || ref->ref_holder != holder;
        mutex_exit(&rc->rc_mtx);
        return (res);
}

EXPORT_SYMBOL(zfs_refcount_create);
EXPORT_SYMBOL(zfs_refcount_destroy);
EXPORT_SYMBOL(zfs_refcount_is_zero);
EXPORT_SYMBOL(zfs_refcount_count);
EXPORT_SYMBOL(zfs_refcount_add);
EXPORT_SYMBOL(zfs_refcount_remove);
EXPORT_SYMBOL(zfs_refcount_held);

/* BEGIN CSTYLED */
ZFS_MODULE_PARAM(zfs, , reference_tracking_enable, INT, ZMOD_RW,
        "Track reference holders to refcount_t objects");

ZFS_MODULE_PARAM(zfs, , reference_history, UINT, ZMOD_RW,
        "Maximum reference holders being tracked");
/* END CSTYLED */
#endif  /* ZFS_DEBUG */