@@ -455,7 +455,7 @@ struct btrfs_full_stripe_locks_tree {
* afterwards represent monotonically decreasing discard filter sizes to
* prioritize what should be discarded next.
*/
-#define BTRFS_NR_DISCARD_LISTS 2
+#define BTRFS_NR_DISCARD_LISTS 3
#define BTRFS_DISCARD_INDEX_UNUSED 0
#define BTRFS_DISCARD_INDEX_START 1
@@ -21,6 +21,10 @@
#define BTRFS_DISCARD_MAX_DELAY (10000UL)
#define BTRFS_DISCARD_MAX_IOPS (10UL)
+/* Montonically decreasing minimum length filters after index 0. */
+static int discard_minlen[BTRFS_NR_DISCARD_LISTS] = {0,
+ BTRFS_ASYNC_DISCARD_MAX_FILTER, BTRFS_ASYNC_DISCARD_MIN_FILTER};
+
static struct list_head *btrfs_get_discard_list(
struct btrfs_discard_ctl *discard_ctl,
struct btrfs_block_group_cache *cache)
@@ -133,16 +137,18 @@ static struct btrfs_block_group_cache *find_next_cache(
* peek_discard_list - wrap find_next_cache()
* @discard_ctl: discard control
* @discard_state: the discard_state of the block_group after state management
+ * @discard_index: the discard_index of the block_group after state management
*
* This wraps find_next_cache() and sets the cache to be in use.
* discard_state's control flow is managed here. Variables related to
* discard_state are reset here as needed (eg discard_cursor). @discard_state
- * is remembered as it may change while we're discarding, but we want the
- * discard to execute in the context determined here.
+ * and @discard_index are remembered as it may change while we're discarding,
+ * but we want the discard to execute in the context determined here.
*/
static struct btrfs_block_group_cache *peek_discard_list(
struct btrfs_discard_ctl *discard_ctl,
- enum btrfs_discard_state *discard_state)
+ enum btrfs_discard_state *discard_state,
+ int *discard_index)
{
struct btrfs_block_group_cache *cache;
u64 now = ktime_get_ns();
@@ -164,6 +170,7 @@ static struct btrfs_block_group_cache *peek_discard_list(
}
discard_ctl->cache = cache;
*discard_state = cache->discard_state;
+ *discard_index = cache->discard_index;
} else {
cache = NULL;
}
@@ -173,6 +180,63 @@ static struct btrfs_block_group_cache *peek_discard_list(
return cache;
}
+/**
+ * btrfs_discard_check_filter - updates a block groups filters
+ * @cache: block group of interest
+ * @bytes: recently freed region size after coalescing
+ *
+ * Async discard maintains multiple lists with progressively smaller filters
+ * to prioritize discarding based on size. Should a free space that matches
+ * a larger filter be returned to the free_space_cache, prioritize that discard
+ * by moving @cache to the proper filter.
+ */
+void btrfs_discard_check_filter(struct btrfs_block_group_cache *cache,
+ u64 bytes)
+{
+ struct btrfs_discard_ctl *discard_ctl;
+
+ if (!cache || !btrfs_test_opt(cache->fs_info, DISCARD_ASYNC))
+ return;
+
+ discard_ctl = &cache->fs_info->discard_ctl;
+
+ if (cache->discard_index > BTRFS_DISCARD_INDEX_START &&
+ bytes >= discard_minlen[cache->discard_index - 1]) {
+ int i;
+
+ remove_from_discard_list(discard_ctl, cache);
+
+ for (i = BTRFS_DISCARD_INDEX_START; i < BTRFS_NR_DISCARD_LISTS;
+ i++) {
+ if (bytes >= discard_minlen[i]) {
+ cache->discard_index = i;
+ btrfs_add_to_discard_list(discard_ctl, cache);
+ break;
+ }
+ }
+ }
+}
+
+/**
+ * btrfs_update_discard_index - moves a block_group along the discard lists
+ * @discard_ctl: discard control
+ * @cache: block_group of interest
+ *
+ * Increment @cache's discard_index. If it falls of the list, let it be.
+ * Otherwise add it back to the appropriate list.
+ */
+static void btrfs_update_discard_index(struct btrfs_discard_ctl *discard_ctl,
+ struct btrfs_block_group_cache *cache)
+{
+ cache->discard_index++;
+ if (cache->discard_index == BTRFS_NR_DISCARD_LISTS) {
+ cache->discard_index = 1;
+ return;
+ }
+
+ btrfs_add_to_discard_list(discard_ctl, cache);
+}
+
/**
* btrfs_discard_cancel_work - remove a block_group from the discard lists
* @discard_ctl: discard control
@@ -289,6 +353,8 @@ static void btrfs_finish_discard_pass(struct btrfs_discard_ctl *discard_ctl,
btrfs_mark_bg_unused(cache);
else
btrfs_add_to_discard_unused_list(discard_ctl, cache);
+ } else {
+ btrfs_update_discard_index(discard_ctl, cache);
}
}
@@ -305,25 +371,41 @@ static void btrfs_discard_workfn(struct work_struct *work)
struct btrfs_discard_ctl *discard_ctl;
struct btrfs_block_group_cache *cache;
enum btrfs_discard_state discard_state;
+ int discard_index = 0;
u64 trimmed = 0;
+ u64 minlen = 0;
discard_ctl = container_of(work, struct btrfs_discard_ctl, work.work);
- cache = peek_discard_list(discard_ctl, &discard_state);
+ cache = peek_discard_list(discard_ctl, &discard_state, &discard_index);
if (!cache || !btrfs_run_discard_work(discard_ctl))
return;
/* Perform discarding. */
- if (discard_state == BTRFS_DISCARD_BITMAPS)
+ minlen = discard_minlen[discard_index];
+
+ if (discard_state == BTRFS_DISCARD_BITMAPS) {
+ u64 maxlen = 0;
+
+ /*
+ * Use the previous levels minimum discard length as the max
+ * length filter. In the case something is added to make a
+ * region go beyond the max filter, the entire bitmap is set
+ * back to BTRFS_TRIM_STATE_UNTRIMMED.
+ */
+ if (discard_index != BTRFS_DISCARD_INDEX_UNUSED)
+ maxlen = discard_minlen[discard_index - 1];
+
btrfs_trim_block_group_bitmaps(cache, &trimmed,
cache->discard_cursor,
btrfs_block_group_end(cache),
- 0, true);
- else
+ minlen, maxlen, true);
+ } else {
btrfs_trim_block_group_extents(cache, &trimmed,
cache->discard_cursor,
btrfs_block_group_end(cache),
- 0, true);
+ minlen, true);
+ }
discard_ctl->prev_discard = trimmed;
@@ -13,12 +13,16 @@ struct btrfs_block_group_cache;
/* Discard size limits. */
#define BTRFS_ASYNC_DISCARD_MAX_SIZE (SZ_64M)
+#define BTRFS_ASYNC_DISCARD_MAX_FILTER (SZ_1M)
+#define BTRFS_ASYNC_DISCARD_MIN_FILTER (SZ_32K)
/* List operations. */
void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
struct btrfs_block_group_cache *cache);
void btrfs_add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
struct btrfs_block_group_cache *cache);
+void btrfs_discard_check_filter(struct btrfs_block_group_cache *cache,
+ u64 bytes);
/* Work operations. */
void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
@@ -2463,6 +2463,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
struct btrfs_block_group_cache *cache = ctl->private;
struct btrfs_free_space *info;
int ret = 0;
+ u64 filter_bytes = bytes;
info = kmem_cache_zalloc(btrfs_free_space_cachep, GFP_NOFS);
if (!info)
@@ -2499,6 +2500,8 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
*/
steal_from_bitmap(ctl, info, true);
+ filter_bytes = max(filter_bytes, info->bytes);
+
ret = link_free_space(ctl, info);
if (ret)
kmem_cache_free(btrfs_free_space_cachep, info);
@@ -2511,8 +2514,10 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
ASSERT(ret != -EEXIST);
}
- if (trim_state != BTRFS_TRIM_STATE_TRIMMED)
+ if (trim_state != BTRFS_TRIM_STATE_TRIMMED) {
+ btrfs_discard_check_filter(cache, filter_bytes);
btrfs_discard_queue_work(&fs_info->discard_ctl, cache);
+ }
return ret;
}
@@ -3453,7 +3458,14 @@ static int trim_no_bitmap(struct btrfs_block_group_cache *block_group,
goto next;
}
unlink_free_space(ctl, entry);
- if (max_discard_size && bytes > max_discard_size) {
+ /*
+ * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+ * If X < BTRFS_ASYNC_DISCARD_MIN_FILTER, we won't trim
+ * X when we come back around. So trim it now.
+ */
+ if (max_discard_size &&
+ bytes >= (max_discard_size +
+ BTRFS_ASYNC_DISCARD_MIN_FILTER)) {
bytes = extent_bytes = max_discard_size;
entry->offset += max_discard_size;
entry->bytes -= max_discard_size;
@@ -3563,7 +3575,7 @@ static void end_trimming_bitmap(struct btrfs_free_space_ctl *ctl,
*/
static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
u64 *total_trimmed, u64 start, u64 end, u64 minlen,
- bool async)
+ u64 maxlen, bool async)
{
struct btrfs_discard_ctl *discard_ctl =
&block_group->fs_info->discard_ctl;
@@ -3591,7 +3603,15 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
}
entry = tree_search_offset(ctl, offset, 1, 0);
- if (!entry || (async && start == offset &&
+ /*
+ * Bitmaps are marked trimmed lossily now to prevent constant
+ * discarding of the same bitmap (the reason why we are bound
+ * by the filters). So, retrim the block group bitmaps when we
+ * are preparing to punt to the unused_bgs list. This uses
+ * @minlen to determine if we are in BTRFS_DISCARD_INDEX_UNUSED
+ * which is the only discard index which sets minlen to 0.
+ */
+ if (!entry || (async && minlen && start == offset &&
btrfs_free_space_trimmed(entry))) {
spin_unlock(&ctl->tree_lock);
mutex_unlock(&ctl->cache_writeout_mutex);
@@ -3612,10 +3632,10 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
if (ret2 || start >= end) {
/*
- * This keeps the invariant that all bytes are trimmed
- * if BTRFS_TRIM_STATE_TRIMMED is set on a bitmap.
+ * We lossily consider a bitmap trimmed if we only skip
+ * over regions <= BTRFS_ASYNC_DISCARD_MIN_FILTER.
*/
- if (ret2 && !minlen)
+ if (ret2 && minlen <= BTRFS_ASYNC_DISCARD_MIN_FILTER)
end_trimming_bitmap(ctl, entry);
else
entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
@@ -3636,14 +3656,20 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
}
bytes = min(bytes, end - start);
- if (bytes < minlen) {
- entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+ if (bytes < minlen || (async && maxlen && bytes > maxlen)) {
spin_unlock(&ctl->tree_lock);
mutex_unlock(&ctl->cache_writeout_mutex);
goto next;
}
- if (async && max_discard_size && bytes > max_discard_size)
+ /*
+ * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+ * If X < @minlen, we won't trim X when we come back around.
+ * So trim it now. We differ here from trimming extents as we
+ * don't keep individual state per bit.
+ */
+ if (async && max_discard_size &&
+ bytes > (max_discard_size + minlen))
bytes = max_discard_size;
bitmap_clear_bits(ctl, entry, start, bytes);
@@ -3749,7 +3775,7 @@ int btrfs_trim_block_group(struct btrfs_block_group_cache *block_group,
if (ret)
goto out;
- ret = trim_bitmaps(block_group, trimmed, start, end, minlen, false);
+ ret = trim_bitmaps(block_group, trimmed, start, end, minlen, 0, false);
/* If we ended in the middle of a bitmap, reset the trimming flag. */
if (end % (BITS_PER_BITMAP * ctl->unit))
reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end));
@@ -3782,7 +3808,7 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group_cache *block_group,
int btrfs_trim_block_group_bitmaps(struct btrfs_block_group_cache *block_group,
u64 *trimmed, u64 start, u64 end, u64 minlen,
- bool async)
+ u64 maxlen, bool async)
{
int ret;
@@ -3796,7 +3822,8 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group_cache *block_group,
btrfs_get_block_group_trimming(block_group);
spin_unlock(&block_group->lock);
- ret = trim_bitmaps(block_group, trimmed, start, end, minlen, async);
+ ret = trim_bitmaps(block_group, trimmed, start, end, minlen, maxlen,
+ async);
btrfs_put_block_group_trimming(block_group);
return ret;
@@ -146,7 +146,7 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group_cache *block_group,
bool async);
int btrfs_trim_block_group_bitmaps(struct btrfs_block_group_cache *block_group,
u64 *trimmed, u64 start, u64 end, u64 minlen,
- bool async);
+ u64 maxlen, bool async);
/* Support functions for running our sanity tests */
#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
Non-block group destruction discarding currently only had a single list with no minimum discard length. This can lead to caravaning more meaningful discards behind a heavily fragmented block group. This adds support for multiple lists with minimum discard lengths to prevent the caravan effect. We promote block groups back up when we exceed the BTRFS_ASYNC_DISCARD_MAX_FILTER size, currently we support only 2 lists with filters of 1MB and 32KB respectively. Signed-off-by: Dennis Zhou <dennis@kernel.org> --- fs/btrfs/ctree.h | 2 +- fs/btrfs/discard.c | 98 ++++++++++++++++++++++++++++++++++--- fs/btrfs/discard.h | 4 ++ fs/btrfs/free-space-cache.c | 53 +++++++++++++++----- fs/btrfs/free-space-cache.h | 2 +- 5 files changed, 136 insertions(+), 23 deletions(-)