From a1f0358b2bf69be216cb6e4ea40fe7ae4d38b8a6 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Tue, 10 Sep 2013 19:07:00 -0700 Subject: [PATCH] bcache: Incremental gc Big garbage collection rewrite; now, garbage collection uses the same mechanisms as used elsewhere for inserting/updating btree node pointers, instead of rewriting interior btree nodes in place. This makes the code significantly cleaner and less fragile, and means we can now make garbage collection incremental - it doesn't have to hold a write lock on the root of the btree for the entire duration of garbage collection. This means that there's less of a latency hit for doing garbage collection, which means we can gc more frequently (and do a better job of reclaiming from the cache), and we can coalesce across more btree nodes (improving our space efficiency). Signed-off-by: Kent Overstreet --- drivers/md/bcache/bcache.h | 1 - drivers/md/bcache/btree.c | 388 ++++++++++++++++++++++++++------------------- drivers/md/bcache/btree.h | 2 +- drivers/md/bcache/sysfs.c | 2 - 4 files changed, 226 insertions(+), 167 deletions(-) diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index d03bc6f..d6970a6 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -477,7 +477,6 @@ struct gc_stat { size_t nkeys; uint64_t data; /* sectors */ - uint64_t dirty; /* sectors */ unsigned in_use; /* percent */ }; diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index a3f8ca4..7d283d2 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1176,12 +1176,10 @@ uint8_t __bch_btree_mark_key(struct cache_set *c, int level, struct bkey *k) #define btree_mark_key(b, k) __bch_btree_mark_key(b->c, b->level, k) -static int btree_gc_mark_node(struct btree *b, unsigned *keys, - struct gc_stat *gc) +static bool btree_gc_mark_node(struct btree *b, struct gc_stat *gc) { uint8_t stale = 0; - unsigned last_dev = -1; - struct bcache_device *d = NULL; + unsigned keys = 0, good_keys = 0; struct bkey *k; struct btree_iter iter; struct bset_tree *t; @@ -1189,27 +1187,17 @@ static int btree_gc_mark_node(struct btree *b, unsigned *keys, gc->nodes++; for_each_key_filter(b, k, &iter, bch_ptr_invalid) { - if (last_dev != KEY_INODE(k)) { - last_dev = KEY_INODE(k); - - d = KEY_INODE(k) < b->c->nr_uuids - ? b->c->devices[last_dev] - : NULL; - } - stale = max(stale, btree_mark_key(b, k)); + keys++; if (bch_ptr_bad(b, k)) continue; - *keys += bkey_u64s(k); - gc->key_bytes += bkey_u64s(k); gc->nkeys++; + good_keys++; gc->data += KEY_SIZE(k); - if (KEY_DIRTY(k)) - gc->dirty += KEY_SIZE(k); } for (t = b->sets; t <= &b->sets[b->nsets]; t++) @@ -1218,79 +1206,74 @@ static int btree_gc_mark_node(struct btree *b, unsigned *keys, bkey_cmp(&b->key, &t->end) < 0, b, "found short btree key in gc"); - return stale; -} + if (b->c->gc_always_rewrite) + return true; -static struct btree *btree_gc_alloc(struct btree *b, struct bkey *k) -{ - /* - * We block priorities from being written for the duration of garbage - * collection, so we can't sleep in btree_alloc() -> - * bch_bucket_alloc_set(), or we'd risk deadlock - so we don't pass it - * our closure. - */ - struct btree *n = btree_node_alloc_replacement(b); - - if (!IS_ERR_OR_NULL(n)) { - swap(b, n); + if (stale > 10) + return true; - memcpy(k->ptr, b->key.ptr, - sizeof(uint64_t) * KEY_PTRS(&b->key)); - - btree_node_free(n); - up_write(&n->lock); - } + if ((keys - good_keys) * 2 > keys) + return true; - return b; + return false; } -/* - * Leaving this at 2 until we've got incremental garbage collection done; it - * could be higher (and has been tested with 4) except that garbage collection - * could take much longer, adversely affecting latency. - */ -#define GC_MERGE_NODES 2U +#define GC_MERGE_NODES 4U struct gc_merge_info { struct btree *b; - struct bkey *k; unsigned keys; }; -static void btree_gc_coalesce(struct btree *b, struct gc_stat *gc, - struct gc_merge_info *r) +static int bch_btree_insert_node(struct btree *, struct btree_op *, + struct keylist *, atomic_t *, struct bkey *); + +static int btree_gc_coalesce(struct btree *b, struct btree_op *op, + struct keylist *keylist, struct gc_stat *gc, + struct gc_merge_info *r) { - unsigned nodes = 0, keys = 0, blocks; - int i; + unsigned i, nodes = 0, keys = 0, blocks; + struct btree *new_nodes[GC_MERGE_NODES]; struct closure cl; + struct bkey *k; + memset(new_nodes, 0, sizeof(new_nodes)); closure_init_stack(&cl); - while (nodes < GC_MERGE_NODES && r[nodes].b) + while (nodes < GC_MERGE_NODES && !IS_ERR_OR_NULL(r[nodes].b)) keys += r[nodes++].keys; blocks = btree_default_blocks(b->c) * 2 / 3; if (nodes < 2 || __set_blocks(b->sets[0].data, keys, b->c) > blocks * (nodes - 1)) - return; - - for (i = nodes - 1; i >= 0; --i) { - if (r[i].b->written) - r[i].b = btree_gc_alloc(r[i].b, r[i].k); + return 0; - if (r[i].b->written) - return; + for (i = 0; i < nodes; i++) { + new_nodes[i] = btree_node_alloc_replacement(r[i].b); + if (IS_ERR_OR_NULL(new_nodes[i])) + goto out_nocoalesce; } for (i = nodes - 1; i > 0; --i) { - struct bset *n1 = r[i].b->sets->data; - struct bset *n2 = r[i - 1].b->sets->data; + struct bset *n1 = new_nodes[i]->sets->data; + struct bset *n2 = new_nodes[i - 1]->sets->data; struct bkey *k, *last = NULL; keys = 0; - if (i == 1) { + if (i > 1) { + for (k = n2->start; + k < end(n2); + k = bkey_next(k)) { + if (__set_blocks(n1, n1->keys + keys + + bkey_u64s(k), b->c) > blocks) + break; + + last = k; + keys += bkey_u64s(k); + } + } else { /* * Last node we're not getting rid of - we're getting * rid of the node at r[0]. Have to try and fit all of @@ -1299,37 +1282,27 @@ static void btree_gc_coalesce(struct btree *b, struct gc_stat *gc, * length keys (shouldn't be possible in practice, * though) */ - if (__set_blocks(n1, n1->keys + r->keys, - b->c) > btree_blocks(r[i].b)) - return; + if (__set_blocks(n1, n1->keys + n2->keys, + b->c) > btree_blocks(new_nodes[i])) + goto out_nocoalesce; keys = n2->keys; + /* Take the key of the node we're getting rid of */ last = &r->b->key; - } else - for (k = n2->start; - k < end(n2); - k = bkey_next(k)) { - if (__set_blocks(n1, n1->keys + keys + - bkey_u64s(k), b->c) > blocks) - break; - - last = k; - keys += bkey_u64s(k); - } + } BUG_ON(__set_blocks(n1, n1->keys + keys, - b->c) > btree_blocks(r[i].b)); + b->c) > btree_blocks(new_nodes[i])); - if (last) { - bkey_copy_key(&r[i].b->key, last); - bkey_copy_key(r[i].k, last); - } + if (last) + bkey_copy_key(&new_nodes[i]->key, last); memcpy(end(n1), n2->start, (void *) node(n2, keys) - (void *) n2->start); n1->keys += keys; + r[i].keys = n1->keys; memmove(n2->start, node(n2, keys), @@ -1337,93 +1310,175 @@ static void btree_gc_coalesce(struct btree *b, struct gc_stat *gc, n2->keys -= keys; - r[i].keys = n1->keys; - r[i - 1].keys = n2->keys; + if (bch_keylist_realloc(keylist, + KEY_PTRS(&new_nodes[i]->key), b->c)) + goto out_nocoalesce; + + bch_btree_node_write(new_nodes[i], &cl); + bch_keylist_add(keylist, &new_nodes[i]->key); } - btree_node_free(r->b); - up_write(&r->b->lock); + for (i = 0; i < nodes; i++) { + if (bch_keylist_realloc(keylist, KEY_PTRS(&r[i].b->key), b->c)) + goto out_nocoalesce; - trace_bcache_btree_gc_coalesce(nodes); + make_btree_freeing_key(r[i].b, keylist->top); + bch_keylist_push(keylist); + } + + /* We emptied out this node */ + BUG_ON(new_nodes[0]->sets->data->keys); + btree_node_free(new_nodes[0]); + rw_unlock(true, new_nodes[0]); + closure_sync(&cl); + + for (i = 0; i < nodes; i++) { + btree_node_free(r[i].b); + rw_unlock(true, r[i].b); + + r[i].b = new_nodes[i]; + } + + bch_btree_insert_node(b, op, keylist, NULL, NULL); + BUG_ON(!bch_keylist_empty(keylist)); + + memmove(r, r + 1, sizeof(r[0]) * (nodes - 1)); + r[nodes - 1].b = ERR_PTR(-EINTR); + + trace_bcache_btree_gc_coalesce(nodes); gc->nodes--; - nodes--; - memmove(&r[0], &r[1], sizeof(struct gc_merge_info) * nodes); - memset(&r[nodes], 0, sizeof(struct gc_merge_info)); + /* Invalidated our iterator */ + return -EINTR; + +out_nocoalesce: + closure_sync(&cl); + + while ((k = bch_keylist_pop(keylist))) + if (!bkey_cmp(k, &ZERO_KEY)) + atomic_dec(&b->c->prio_blocked); + + for (i = 0; i < nodes; i++) + if (!IS_ERR_OR_NULL(new_nodes[i])) { + btree_node_free(new_nodes[i]); + rw_unlock(true, new_nodes[i]); + } + return 0; } -static int btree_gc_recurse(struct btree *b, struct btree_op *op, - struct closure *writes, struct gc_stat *gc) +static unsigned btree_gc_count_keys(struct btree *b) { - void write(struct btree *r) - { - if (!r->written || btree_node_dirty(r)) - bch_btree_node_write(r, writes); + struct bkey *k; + struct btree_iter iter; + unsigned ret = 0; - up_write(&r->lock); - } + for_each_key_filter(b, k, &iter, bch_ptr_bad) + ret += bkey_u64s(k); - int ret = 0, stale; + return ret; +} + +static int btree_gc_recurse(struct btree *b, struct btree_op *op, + struct closure *writes, struct gc_stat *gc) +{ unsigned i; + int ret = 0; + bool should_rewrite; + struct btree *n; + struct bkey *k; + struct keylist keys; + struct btree_iter iter; struct gc_merge_info r[GC_MERGE_NODES]; + struct gc_merge_info *last = r + GC_MERGE_NODES - 1; - memset(r, 0, sizeof(r)); + bch_keylist_init(&keys); + bch_btree_iter_init(b, &iter, &b->c->gc_done); - while ((r->k = bch_next_recurse_key(b, &b->c->gc_done))) { - r->b = bch_btree_node_get(b->c, r->k, b->level - 1, true); + for (i = 0; i < GC_MERGE_NODES; i++) + r[i].b = ERR_PTR(-EINTR); - if (IS_ERR(r->b)) { - ret = PTR_ERR(r->b); - break; + while (1) { + k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad); + if (k) { + r->b = bch_btree_node_get(b->c, k, b->level - 1, true); + if (IS_ERR(r->b)) { + ret = PTR_ERR(r->b); + break; + } + + r->keys = btree_gc_count_keys(r->b); + + ret = btree_gc_coalesce(b, op, &keys, gc, r); + if (ret) + break; } - r->keys = 0; - stale = btree_gc_mark_node(r->b, &r->keys, gc); + if (!last->b) + break; - if (!b->written && - (r->b->level || stale > 10 || - b->c->gc_always_rewrite)) - r->b = btree_gc_alloc(r->b, r->k); + if (!IS_ERR(last->b)) { + should_rewrite = btree_gc_mark_node(last->b, gc); + if (should_rewrite) { + n = btree_node_alloc_replacement(last->b); - if (r->b->level) - ret = btree_gc_recurse(r->b, op, writes, gc); + if (!IS_ERR_OR_NULL(n)) { + bch_btree_node_write_sync(n); + bch_keylist_add(&keys, &n->key); - if (ret) { - write(r->b); - break; - } + make_btree_freeing_key(last->b, + keys.top); + bch_keylist_push(&keys); + + btree_node_free(last->b); - bkey_copy_key(&b->c->gc_done, r->k); + bch_btree_insert_node(b, op, &keys, + NULL, NULL); + BUG_ON(!bch_keylist_empty(&keys)); - if (!b->written) - btree_gc_coalesce(b, gc, r); + rw_unlock(true, last->b); + last->b = n; + + /* Invalidated our iterator */ + ret = -EINTR; + break; + } + } - if (r[GC_MERGE_NODES - 1].b) - write(r[GC_MERGE_NODES - 1].b); + if (last->b->level) { + ret = btree_gc_recurse(last->b, op, writes, gc); + if (ret) + break; + } - memmove(&r[1], &r[0], - sizeof(struct gc_merge_info) * (GC_MERGE_NODES - 1)); + bkey_copy_key(&b->c->gc_done, &last->b->key); + + /* + * Must flush leaf nodes before gc ends, since replace + * operations aren't journalled + */ + if (btree_node_dirty(last->b)) + bch_btree_node_write(last->b, writes); + rw_unlock(true, last->b); + } + + memmove(r + 1, r, sizeof(r[0]) * (GC_MERGE_NODES - 1)); + r->b = NULL; - /* When we've got incremental GC working, we'll want to do - * if (should_resched()) - * return -EAGAIN; - */ - cond_resched(); -#if 0 if (need_resched()) { ret = -EAGAIN; break; } -#endif } - for (i = 1; i < GC_MERGE_NODES && r[i].b; i++) - write(r[i].b); + for (i = 0; i < GC_MERGE_NODES; i++) + if (!IS_ERR_OR_NULL(r[i].b)) { + if (btree_node_dirty(r[i].b)) + bch_btree_node_write(r[i].b, writes); + rw_unlock(true, r[i].b); + } - /* Might have freed some children, must remove their keys */ - if (!b->written) - bch_btree_sort(b); + bch_keylist_free(&keys); return ret; } @@ -1432,27 +1487,31 @@ static int bch_btree_gc_root(struct btree *b, struct btree_op *op, struct closure *writes, struct gc_stat *gc) { struct btree *n = NULL; - unsigned keys = 0; - int ret = 0, stale = btree_gc_mark_node(b, &keys, gc); + int ret = 0; + bool should_rewrite; - if (b->level || stale > 10) + should_rewrite = btree_gc_mark_node(b, gc); + if (should_rewrite) { n = btree_node_alloc_replacement(b); - if (!IS_ERR_OR_NULL(n)) - swap(b, n); - - if (b->level) - ret = btree_gc_recurse(b, op, writes, gc); + if (!IS_ERR_OR_NULL(n)) { + bch_btree_node_write_sync(n); + bch_btree_set_root(n); + btree_node_free(b); + rw_unlock(true, n); - if (!b->written || btree_node_dirty(b)) - bch_btree_node_write_sync(b); + return -EINTR; + } + } - if (!IS_ERR_OR_NULL(n)) { - bch_btree_set_root(b); - btree_node_free(n); - rw_unlock(true, b); + if (b->level) { + ret = btree_gc_recurse(b, op, writes, gc); + if (ret) + return ret; } + bkey_copy_key(&b->c->gc_done, &b->key); + return ret; } @@ -1550,29 +1609,20 @@ static void bch_btree_gc(struct cache_set *c) btree_gc_start(c); - atomic_inc(&c->prio_blocked); - - ret = btree_root(gc_root, c, &op, &writes, &stats); - closure_sync(&writes); - - if (ret) { - pr_warn("gc failed!"); - return; - } + do { + ret = btree_root(gc_root, c, &op, &writes, &stats); + closure_sync(&writes); - /* Possibly wait for new UUIDs or whatever to hit disk */ - bch_journal_meta(c, &writes); - closure_sync(&writes); + if (ret && ret != -EAGAIN) + pr_warn("gc failed!"); + } while (ret); available = bch_btree_gc_finish(c); - - atomic_dec(&c->prio_blocked); wake_up_allocators(c); bch_time_stats_update(&c->btree_gc_time, start_time); stats.key_bytes *= sizeof(uint64_t); - stats.dirty <<= 9; stats.data <<= 9; stats.in_use = (c->nbuckets - available) * 100 / c->nbuckets; memcpy(&c->gc_stats, &stats, sizeof(struct gc_stat)); @@ -1585,14 +1635,28 @@ static void bch_btree_gc(struct cache_set *c) static int bch_gc_thread(void *arg) { struct cache_set *c = arg; + struct cache *ca; + unsigned i; while (1) { +again: bch_btree_gc(c); set_current_state(TASK_INTERRUPTIBLE); if (kthread_should_stop()) break; + mutex_lock(&c->bucket_lock); + + for_each_cache(ca, c, i) + if (ca->invalidate_needs_gc) { + mutex_unlock(&c->bucket_lock); + set_current_state(TASK_RUNNING); + goto again; + } + + mutex_unlock(&c->bucket_lock); + try_to_freeze(); schedule(); } @@ -2083,8 +2147,6 @@ static int bch_btree_insert_node(struct btree *b, struct btree_op *op, bch_keylist_init(&split_keys); - BUG_ON(b->level); - do { BUG_ON(b->level && replace_key); diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h index e11bb85..b5a46af 100644 --- a/drivers/md/bcache/btree.h +++ b/drivers/md/bcache/btree.h @@ -201,7 +201,7 @@ static inline bool bkey_written(struct btree *b, struct bkey *k) static inline void set_gc_sectors(struct cache_set *c) { - atomic_set(&c->sectors_to_gc, c->sb.bucket_size * c->nbuckets / 8); + atomic_set(&c->sectors_to_gc, c->sb.bucket_size * c->nbuckets / 16); } static inline struct bkey *bch_btree_iter_init(struct btree *b, diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c index 9687771..c5f73e3 100644 --- a/drivers/md/bcache/sysfs.c +++ b/drivers/md/bcache/sysfs.c @@ -489,7 +489,6 @@ lock_root: sysfs_print(btree_used_percent, btree_used(c)); sysfs_print(btree_nodes, c->gc_stats.nodes); - sysfs_hprint(dirty_data, c->gc_stats.dirty); sysfs_hprint(average_key_size, average_key_size(c)); sysfs_print(cache_read_races, @@ -642,7 +641,6 @@ static struct attribute *bch_cache_set_files[] = { &sysfs_cache_available_percent, &sysfs_average_key_size, - &sysfs_dirty_data, &sysfs_errors, &sysfs_io_error_limit, -- 2.7.4