From: Kai Krakow kai@kaishome.de

This reverts commit 56b30770b27d54d68ad51eccc6d888282b568cee.

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 --- drivers/md/bcache/bcache.h | 2 ++ drivers/md/bcache/btree.c | 21 +++++++++++++++++++-- drivers/md/bcache/super.c | 4 ++++ 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index d7a84327b7f1..2b8c7dd2cfae 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -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 */ diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 910df242c83d..952f022db5a5 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -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; +} diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index e7d1b52c5cc8..85a44a0cffe0 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -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;