From: Dennis Zhou <dennis@kernel.org>
To: David Sterba <dsterba@suse.com>, Chris Mason <clm@fb.com>,
Josef Bacik <josef@toxicpanda.com>,
Omar Sandoval <osandov@osandov.com>
Cc: kernel-team@fb.com, linux-btrfs@vger.kernel.org,
Dennis Zhou <dennis@kernel.org>
Subject: [PATCH 17/22] btrfs: have multiple discard lists
Date: Wed, 20 Nov 2019 16:51:16 -0500
Message-ID: <3a0ed1211af6aea8e281642c042e9c4ee2cf6a1c.1574282259.git.dennis@kernel.org> (raw)
In-Reply-To: <cover.1574282259.git.dennis@kernel.org>
In-Reply-To: <cover.1574282259.git.dennis@kernel.org>
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>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/ctree.h | 2 +-
fs/btrfs/discard.c | 101 +++++++++++++++++++++++++++++++++---
fs/btrfs/discard.h | 4 ++
fs/btrfs/free-space-cache.c | 53 ++++++++++++++-----
fs/btrfs/free-space-cache.h | 2 +-
5 files changed, 139 insertions(+), 23 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 37ad60913092..52f69aaaa19c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -457,7 +457,7 @@ 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
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index cd7293fe8aa9..05e99adb149b 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -19,6 +19,10 @@
#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 *block_group)
@@ -131,16 +135,18 @@ static struct btrfs_block_group *find_next_block_group(
* peek_discard_list - wrap find_next_block_group()
* @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_block_group() and sets the block_group 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 *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 *block_group;
u64 now = ktime_get_ns();
@@ -162,6 +168,7 @@ static struct btrfs_block_group *peek_discard_list(
}
discard_ctl->block_group = block_group;
*discard_state = block_group->discard_state;
+ *discard_index = block_group->discard_index;
} else {
block_group = NULL;
}
@@ -171,6 +178,65 @@ static struct btrfs_block_group *peek_discard_list(
return block_group;
}
+/**
+ * btrfs_discard_check_filter - updates a block groups filters
+ * @block_group: 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 @block_group to the proper filter.
+ */
+void btrfs_discard_check_filter(struct btrfs_block_group *block_group,
+ u64 bytes)
+{
+ struct btrfs_discard_ctl *discard_ctl;
+
+ if (!block_group ||
+ !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+ return;
+
+ discard_ctl = &block_group->fs_info->discard_ctl;
+
+ if (block_group->discard_index > BTRFS_DISCARD_INDEX_START &&
+ bytes >= discard_minlen[block_group->discard_index - 1]) {
+ int i;
+
+ remove_from_discard_list(discard_ctl, block_group);
+
+ for (i = BTRFS_DISCARD_INDEX_START; i < BTRFS_NR_DISCARD_LISTS;
+ i++) {
+ if (bytes >= discard_minlen[i]) {
+ block_group->discard_index = i;
+ btrfs_add_to_discard_list(discard_ctl,
+ block_group);
+ break;
+ }
+ }
+ }
+}
+
+/**
+ * btrfs_update_discard_index - moves a block_group along the discard lists
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * Increment @block_group'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 *block_group)
+{
+ block_group->discard_index++;
+ if (block_group->discard_index == BTRFS_NR_DISCARD_LISTS) {
+ block_group->discard_index = 1;
+ return;
+ }
+
+ btrfs_add_to_discard_list(discard_ctl, block_group);
+}
+
/**
* btrfs_discard_cancel_work - remove a block_group from the discard lists
* @discard_ctl: discard control
@@ -292,6 +358,8 @@ static void btrfs_finish_discard_pass(struct btrfs_discard_ctl *discard_ctl,
else
btrfs_add_to_discard_unused_list(discard_ctl,
block_group);
+ } else {
+ btrfs_update_discard_index(discard_ctl, block_group);
}
}
@@ -308,25 +376,42 @@ static void btrfs_discard_workfn(struct work_struct *work)
struct btrfs_discard_ctl *discard_ctl;
struct btrfs_block_group *block_group;
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);
- block_group = peek_discard_list(discard_ctl, &discard_state);
+ block_group = peek_discard_list(discard_ctl, &discard_state,
+ &discard_index);
if (!block_group || !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(block_group, &trimmed,
block_group->discard_cursor,
btrfs_block_group_end(block_group),
- 0, true);
- else
+ minlen, maxlen, true);
+ } else {
btrfs_trim_block_group_extents(block_group, &trimmed,
block_group->discard_cursor,
btrfs_block_group_end(block_group),
- 0, true);
+ minlen, true);
+ }
discard_ctl->prev_discard = trimmed;
diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
index e1819f319901..9dbc25bede08 100644
--- a/fs/btrfs/discard.h
+++ b/fs/btrfs/discard.h
@@ -11,12 +11,16 @@ struct btrfs_block_group;
/* 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 *block_group);
void btrfs_add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
struct btrfs_block_group *block_group);
+void btrfs_discard_check_filter(struct btrfs_block_group *block_group,
+ u64 bytes);
/* Work operations. */
void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 9f6befd50b44..b1b07af63efd 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2466,6 +2466,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
struct btrfs_block_group *block_group = 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)
@@ -2502,6 +2503,8 @@ 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);
@@ -2514,8 +2517,10 @@ 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(block_group, filter_bytes);
btrfs_discard_queue_work(&fs_info->discard_ctl, block_group);
+ }
return ret;
}
@@ -3455,7 +3460,14 @@ static int trim_no_bitmap(struct btrfs_block_group *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;
@@ -3565,7 +3577,7 @@ static void end_trimming_bitmap(struct btrfs_free_space_ctl *ctl,
*/
static int trim_bitmaps(struct btrfs_block_group *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;
@@ -3593,7 +3605,15 @@ static int trim_bitmaps(struct btrfs_block_group *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);
@@ -3614,10 +3634,10 @@ static int trim_bitmaps(struct btrfs_block_group *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;
@@ -3638,14 +3658,20 @@ static int trim_bitmaps(struct btrfs_block_group *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);
@@ -3751,7 +3777,7 @@ int btrfs_trim_block_group(struct btrfs_block_group *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));
@@ -3784,7 +3810,7 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
u64 *trimmed, u64 start, u64 end, u64 minlen,
- bool async)
+ u64 maxlen, bool async)
{
int ret;
@@ -3798,7 +3824,8 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *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;
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index b61b52eeaaf3..7c6d95765979 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -144,7 +144,7 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
bool async);
int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *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
--
2.17.1
next prev parent reply index
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 21:50 [PATCH v3 00/22] btrfs: async discard support Dennis Zhou
2019-11-20 21:51 ` [PATCH 01/22] bitmap: genericize percpu bitmap region iterators Dennis Zhou
2019-11-20 21:51 ` [PATCH 02/22] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
2019-11-20 21:51 ` [PATCH 03/22] btrfs: keep track of which extents have been discarded Dennis Zhou
2019-11-20 21:51 ` [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
2019-11-23 0:17 ` kbuild test robot
2019-11-25 13:59 ` David Sterba
2019-11-25 19:37 ` Dennis Zhou
2019-11-20 21:51 ` [PATCH 05/22] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
2019-11-20 21:51 ` [PATCH 06/22] btrfs: handle empty block_group removal Dennis Zhou
2019-11-20 21:51 ` [PATCH 07/22] btrfs: discard one region at a time in async discard Dennis Zhou
2019-11-20 21:51 ` [PATCH 08/22] btrfs: add removal calls for sysfs debug/ Dennis Zhou
2019-11-20 21:51 ` [PATCH 09/22] btrfs: make UUID/debug have its own kobject Dennis Zhou
2019-11-20 21:51 ` [PATCH 10/22] btrfs: add discard sysfs directory Dennis Zhou
2019-11-20 21:51 ` [PATCH 11/22] btrfs: track discardable extents for async discard Dennis Zhou
2019-11-20 21:51 ` [PATCH 12/22] btrfs: keep track of discardable_bytes Dennis Zhou
2019-11-20 21:51 ` [PATCH 13/22] btrfs: calculate discard delay based on number of extents Dennis Zhou
2019-11-20 21:51 ` [PATCH 14/22] btrfs: add bps discard rate limit Dennis Zhou
2019-11-20 21:51 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
2019-11-20 21:51 ` [PATCH 16/22] btrfs: make max async discard size tunable Dennis Zhou
2019-11-20 21:51 ` Dennis Zhou [this message]
2019-11-20 21:51 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-11-20 21:51 ` [PATCH 19/22] btrfs: keep track of discard reuse stats Dennis Zhou
2019-11-20 21:51 ` [PATCH 20/22] btrfs: add async discard header Dennis Zhou
2019-11-20 21:51 ` [PATCH 21/22] btrfs: increase the metadata allowance for the free_space_cache Dennis Zhou
2019-11-20 21:51 ` [PATCH 22/22] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
-- strict thread matches above, loose matches on Subject: below --
2019-12-14 0:22 [PATCH v6 00/22] btrfs: async discard support Dennis Zhou
2019-12-14 0:22 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
2019-12-09 19:45 [PATCH v5 00/22] btrfs: async discard support Dennis Zhou
2019-12-09 19:46 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
2019-11-25 19:46 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
2019-10-23 22:52 [PATCH v2 00/22] btrfs: async discard support Dennis Zhou
2019-10-23 22:53 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
2019-11-08 19:44 ` Josef Bacik
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