Commit 9f233ffe authored by Kai Krakow's avatar Kai Krakow Committed by Jens Axboe
Browse files

Revert "bcache: Kill btree_io_wq" 



This reverts commit 56b30770.

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 56b30770 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: default avatarKai Krakow <kai@kaishome.de>
Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d7fae7b4

drivers/md/bcache/bcache.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

drivers/md/bcache/btree.c

+19 −2
Original line number Diff line number Diff line
@@ -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;

}

drivers/md/bcache/super.c

+4 −0
Original line number Diff line number Diff line
@@ -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;