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Revert "bcache: Kill btree_io_wq"

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This reverts commit 56b30770b2.

With the btree using the `system_wq`, I seem to see a lot more desktop
latency than I should.

After some more investigation, it looks like the original assumption
of 56b3077 no longer is true, and bcache has a very high potential of
congesting the `system_wq`. In turn, this introduces laggy desktop
performance, IO stalls (at least with btrfs), and input events may be
delayed.

So let's revert this. It's important to note that the semantics of
using `system_wq` previously mean that `btree_io_wq` should be created
before and destroyed after other bcache wqs to keep the same
assumptions.

Cc: Coly Li <colyli@suse.de>
Cc: stable@vger.kernel.org # 5.4+
Signed-off-by: Kai Krakow <kai@kaishome.de>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Kai Krakow 2021-02-10 13:07:25 +08:00 committed by Jens Axboe
parent d7fae7b4fa
commit 9f233ffe02
3 changed files with 25 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/md/bcache/bcache.h
View File

@ -1046,5 +1046,7 @@ void bch_debug_exit(void);
void bch_debug_init(void);
void bch_request_exit(void);
int bch_request_init(void);
void bch_btree_exit(void);
int bch_btree_init(void);
#endif /* _BCACHE_H */

21
drivers/md/bcache/btree.c
View File

@ -99,6 +99,8 @@
#define PTR_HASH(c, k) \
(((k)->ptr[0] >> c->bucket_bits) | PTR_GEN(k, 0))
static struct workqueue_struct *btree_io_wq;
#define insert_lock(s, b) ((b)->level <= (s)->lock)
@ -308,7 +310,7 @@ static void __btree_node_write_done(struct closure *cl)
btree_complete_write(b, w);
if (btree_node_dirty(b))
schedule_delayed_work(&b->work, 30 * HZ);
queue_delayed_work(btree_io_wq, &b->work, 30 * HZ);
closure_return_with_destructor(cl, btree_node_write_unlock);
}
@ -481,7 +483,7 @@ static void bch_btree_leaf_dirty(struct btree *b, atomic_t *journal_ref)
BUG_ON(!i->keys);
if (!btree_node_dirty(b))
schedule_delayed_work(&b->work, 30 * HZ);
queue_delayed_work(btree_io_wq, &b->work, 30 * HZ);
set_btree_node_dirty(b);
@ -2764,3 +2766,18 @@ void bch_keybuf_init(struct keybuf *buf)
spin_lock_init(&buf->lock);
array_allocator_init(&buf->freelist);
}
void bch_btree_exit(void)
{
if (btree_io_wq)
destroy_workqueue(btree_io_wq);
}
int __init bch_btree_init(void)
{
btree_io_wq = create_singlethread_workqueue("bch_btree_io");
if (!btree_io_wq)
return -ENOMEM;
return 0;
}

4
drivers/md/bcache/super.c
View File

@ -2821,6 +2821,7 @@ static void bcache_exit(void)
destroy_workqueue(bcache_wq);
if (bch_journal_wq)
destroy_workqueue(bch_journal_wq);
bch_btree_exit();
if (bcache_major)
unregister_blkdev(bcache_major, "bcache");
@ -2876,6 +2877,9 @@ static int __init bcache_init(void)
return bcache_major;
}
if (bch_btree_init())
goto err;
bcache_wq = alloc_workqueue("bcache", WQ_MEM_RECLAIM, 0);
if (!bcache_wq)
goto err;