From 8e7102273f597dbb38af43da874f8c123f8e6dbe Mon Sep 17 00:00:00 2001 From: Coly Li Date: Sun, 22 Mar 2020 14:03:01 +0800 Subject: bcache: make bch_btree_check() to be multithreaded When registering a cache device, bch_btree_check() is called to check all btree nodes, to make sure the btree is consistent and not corrupted. bch_btree_check() is recursively executed in a single thread, when there are a lot of data cached and the btree is huge, it may take very long time to check all the btree nodes. In my testing, I observed it took around 50 minutes to finish bch_btree_check(). When checking the bcache btree nodes, the cache set is not running yet, and indeed the whole tree is in read-only state, it is safe to create multiple threads to check the btree in parallel. This patch tries to create multiple threads, and each thread tries to one-by-one check the sub-tree indexed by a key from the btree root node. The parallel thread number depends on how many keys in the btree root node. At most BCH_BTR_CHKTHREAD_MAX (64) threads can be created, but in practice is should be min(cpu-number/2, root-node-keys-number). Signed-off-by: Coly Li Cc: Christoph Hellwig Signed-off-by: Jens Axboe --- drivers/md/bcache/btree.c | 169 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 166 insertions(+), 3 deletions(-) (limited to 'drivers/md/bcache/btree.c') diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index faf152524a16..74d66b641169 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1897,13 +1897,176 @@ static int bch_btree_check_recurse(struct btree *b, struct btree_op *op) return ret; } + +static int bch_btree_check_thread(void *arg) +{ + int ret; + struct btree_check_info *info = arg; + struct btree_check_state *check_state = info->state; + struct cache_set *c = check_state->c; + struct btree_iter iter; + struct bkey *k, *p; + int cur_idx, prev_idx, skip_nr; + int i, n; + + k = p = NULL; + i = n = 0; + cur_idx = prev_idx = 0; + ret = 0; + + /* root node keys are checked before thread created */ + bch_btree_iter_init(&c->root->keys, &iter, NULL); + k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad); + BUG_ON(!k); + + p = k; + while (k) { + /* + * Fetch a root node key index, skip the keys which + * should be fetched by other threads, then check the + * sub-tree indexed by the fetched key. + */ + spin_lock(&check_state->idx_lock); + cur_idx = check_state->key_idx; + check_state->key_idx++; + spin_unlock(&check_state->idx_lock); + + skip_nr = cur_idx - prev_idx; + + while (skip_nr) { + k = bch_btree_iter_next_filter(&iter, + &c->root->keys, + bch_ptr_bad); + if (k) + p = k; + else { + /* + * No more keys to check in root node, + * current checking threads are enough, + * stop creating more. + */ + atomic_set(&check_state->enough, 1); + /* Update check_state->enough earlier */ + smp_mb(); + goto out; + } + skip_nr--; + cond_resched(); + } + + if (p) { + struct btree_op op; + + btree_node_prefetch(c->root, p); + c->gc_stats.nodes++; + bch_btree_op_init(&op, 0); + ret = bcache_btree(check_recurse, p, c->root, &op); + if (ret) + goto out; + } + p = NULL; + prev_idx = cur_idx; + cond_resched(); + } + +out: + info->result = ret; + /* update check_state->started among all CPUs */ + smp_mb(); + if (atomic_dec_and_test(&check_state->started)) + wake_up(&check_state->wait); + + return ret; +} + + + +static int bch_btree_chkthread_nr(void) +{ + int n = num_online_cpus()/2; + + if (n == 0) + n = 1; + else if (n > BCH_BTR_CHKTHREAD_MAX) + n = BCH_BTR_CHKTHREAD_MAX; + + return n; +} + int bch_btree_check(struct cache_set *c) { - struct btree_op op; + int ret = 0; + int i; + struct bkey *k = NULL; + struct btree_iter iter; + struct btree_check_state *check_state; + char name[32]; - bch_btree_op_init(&op, SHRT_MAX); + /* check and mark root node keys */ + for_each_key_filter(&c->root->keys, k, &iter, bch_ptr_invalid) + bch_initial_mark_key(c, c->root->level, k); + + bch_initial_mark_key(c, c->root->level + 1, &c->root->key); + + if (c->root->level == 0) + return 0; + + check_state = kzalloc(sizeof(struct btree_check_state), GFP_KERNEL); + if (!check_state) + return -ENOMEM; + + check_state->c = c; + check_state->total_threads = bch_btree_chkthread_nr(); + check_state->key_idx = 0; + spin_lock_init(&check_state->idx_lock); + atomic_set(&check_state->started, 0); + atomic_set(&check_state->enough, 0); + init_waitqueue_head(&check_state->wait); - return bcache_btree_root(check_recurse, c, &op); + /* + * Run multiple threads to check btree nodes in parallel, + * if check_state->enough is non-zero, it means current + * running check threads are enough, unncessary to create + * more. + */ + for (i = 0; i < check_state->total_threads; i++) { + /* fetch latest check_state->enough earlier */ + smp_mb(); + if (atomic_read(&check_state->enough)) + break; + + check_state->infos[i].result = 0; + check_state->infos[i].state = check_state; + snprintf(name, sizeof(name), "bch_btrchk[%u]", i); + atomic_inc(&check_state->started); + + check_state->infos[i].thread = + kthread_run(bch_btree_check_thread, + &check_state->infos[i], + name); + if (IS_ERR(check_state->infos[i].thread)) { + pr_err("fails to run thread bch_btrchk[%d]", i); + for (--i; i >= 0; i--) + kthread_stop(check_state->infos[i].thread); + ret = -ENOMEM; + goto out; + } + } + + wait_event_interruptible(check_state->wait, + atomic_read(&check_state->started) == 0 || + test_bit(CACHE_SET_IO_DISABLE, &c->flags)); + + for (i = 0; i < check_state->total_threads; i++) { + if (check_state->infos[i].result) { + ret = check_state->infos[i].result; + goto out; + } + } + +out: + kfree(check_state); + return ret; } void bch_initial_gc_finish(struct cache_set *c) -- cgit v1.2.3