Btrfs: Wait for kernel threads to make progress during async submission
Before this change, btrfs would use a bdi congestion function to make
sure there weren't too many pending async checksum work items.
This change makes the process creating async work items wait instead,
leading to fewer congestion returns from the bdi. This improves
pdflush background_writeout scanning.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 5f2f5a8..958cd8b 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -48,6 +48,7 @@
/* number of things on the pending list */
atomic_t num_pending;
+ unsigned long sequence;
/* protects the pending list. */
spinlock_t lock;
@@ -197,6 +198,7 @@
spin_lock_irq(&workers->lock);
list_add_tail(&worker->worker_list, &workers->idle_list);
+ worker->idle = 1;
workers->num_workers++;
spin_unlock_irq(&workers->lock);
}
@@ -238,7 +240,10 @@
*/
next = workers->worker_list.next;
worker = list_entry(next, struct btrfs_worker_thread, worker_list);
- list_move_tail(next, &workers->worker_list);
+ atomic_inc(&worker->num_pending);
+ worker->sequence++;
+ if (worker->sequence % 4 == 0)
+ list_move_tail(next, &workers->worker_list);
return worker;
}
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index bb4a8d2..0402133 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -526,6 +526,7 @@
struct btrfs_transaction *running_transaction;
wait_queue_head_t transaction_throttle;
wait_queue_head_t transaction_wait;
+ wait_queue_head_t async_submit_wait;
struct btrfs_super_block super_copy;
struct btrfs_super_block super_for_commit;
struct block_device *__bdev;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1bf210d..1aed1f4 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -429,31 +429,36 @@
return 0;
}
+static unsigned long async_submit_limit(struct btrfs_fs_info *info)
+{
+ unsigned long limit = min_t(unsigned long,
+ info->workers.max_workers,
+ info->fs_devices->open_devices);
+ return 256 * limit;
+}
+
int btrfs_congested_async(struct btrfs_fs_info *info, int iodone)
{
- int limit = 256 * info->fs_devices->open_devices;
-
- if (iodone)
- limit = (limit * 3) / 2;
- if (atomic_read(&info->nr_async_submits) > limit)
- return 1;
-
- return atomic_read(&info->nr_async_bios) > limit;
+ return atomic_read(&info->nr_async_bios) > async_submit_limit(info);
}
static void run_one_async_submit(struct btrfs_work *work)
{
struct btrfs_fs_info *fs_info;
struct async_submit_bio *async;
+ int limit;
async = container_of(work, struct async_submit_bio, work);
fs_info = BTRFS_I(async->inode)->root->fs_info;
+
+ limit = async_submit_limit(fs_info);
+ limit = limit * 2 / 3;
+
atomic_dec(&fs_info->nr_async_submits);
- if ((async->bio->bi_rw & (1 << BIO_RW)) &&
- !btrfs_congested_async(fs_info, 1)) {
- clear_bdi_congested(&fs_info->bdi, WRITE);
- }
+ if (atomic_read(&fs_info->nr_async_submits) < limit)
+ wake_up(&fs_info->async_submit_wait);
+
async->submit_bio_hook(async->inode, async->rw, async->bio,
async->mirror_num);
kfree(async);
@@ -464,6 +469,7 @@
extent_submit_bio_hook_t *submit_bio_hook)
{
struct async_submit_bio *async;
+ int limit = async_submit_limit(fs_info);
async = kmalloc(sizeof(*async), GFP_NOFS);
if (!async)
@@ -478,6 +484,10 @@
async->work.flags = 0;
atomic_inc(&fs_info->nr_async_submits);
btrfs_queue_worker(&fs_info->workers, &async->work);
+
+ wait_event_timeout(fs_info->async_submit_wait,
+ (atomic_read(&fs_info->nr_async_submits) < limit),
+ HZ/10);
return 0;
}
@@ -545,16 +555,11 @@
if (wbc->sync_mode == WB_SYNC_NONE) {
u64 num_dirty;
u64 start = 0;
- unsigned long thresh = 96 * 1024 * 1024;
+ unsigned long thresh = 8 * 1024 * 1024;
if (wbc->for_kupdate)
return 0;
- if (current_is_pdflush()) {
- thresh = 96 * 1024 * 1024;
- } else {
- thresh = 8 * 1024 * 1024;
- }
num_dirty = count_range_bits(tree, &start, (u64)-1,
thresh, EXTENT_DIRTY);
if (num_dirty < thresh) {
@@ -1333,6 +1338,7 @@
mutex_init(&fs_info->volume_mutex);
init_waitqueue_head(&fs_info->transaction_throttle);
init_waitqueue_head(&fs_info->transaction_wait);
+ init_waitqueue_head(&fs_info->async_submit_wait);
#if 0
ret = add_hasher(fs_info, "crc32c");
@@ -1380,6 +1386,7 @@
* devices
*/
fs_info->submit_workers.idle_thresh = 64;
+ fs_info->workers.idle_thresh = 32;
btrfs_init_workers(&fs_info->fixup_workers, "fixup", 1);
btrfs_init_workers(&fs_info->endio_workers, "endio",
@@ -1849,7 +1856,7 @@
struct extent_io_tree *tree;
u64 num_dirty;
u64 start = 0;
- unsigned long thresh = 2 * 1024 * 1024;
+ unsigned long thresh = 12 * 1024 * 1024;
tree = &BTRFS_I(root->fs_info->btree_inode)->io_tree;
if (current_is_pdflush())