From: Kai Krakow kai@kaishome.de

This is potentially long running and not latency sensitive, let's get it out of the way of other latency sensitive events.

As observed in the previous commit, the `system_wq` comes easily congested by bcache, and this fixes a few more stalls I was observing every once in a while.

Let's not make this `WQ_MEM_RECLAIM` as it showed to reduce performance of boot and file system operations in my tests. Also, without `WQ_MEM_RECLAIM`, I no longer see desktop stalls. This matches the previous behavior as `system_wq` also does no memory reclaim:

// workqueue.c: system_wq = alloc_workqueue("events", 0, 0);

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 | 1 + drivers/md/bcache/journal.c | 4 ++-- drivers/md/bcache/super.c | 16 ++++++++++++++++ 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 2b8c7dd2cfae..848dd4db1659 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -1005,6 +1005,7 @@ void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent);

extern struct workqueue_struct *bcache_wq; extern struct workqueue_struct *bch_journal_wq; +extern struct workqueue_struct *bch_flush_wq; extern struct mutex bch_register_lock; extern struct list_head bch_cache_sets;

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c index aefbdb7e003b..c6613e817333 100644 --- a/drivers/md/bcache/journal.c +++ b/drivers/md/bcache/journal.c @@ -932,8 +932,8 @@ atomic_t *bch_journal(struct cache_set *c, journal_try_write(c); } else if (!w->dirty) { w->dirty = true; - schedule_delayed_work(&c->journal.work, - msecs_to_jiffies(c->journal_delay_ms)); + queue_delayed_work(bch_flush_wq, &c->journal.work, + msecs_to_jiffies(c->journal_delay_ms)); spin_unlock(&c->journal.lock); } else { spin_unlock(&c->journal.lock); diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 85a44a0cffe0..0228ccb293fc 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -49,6 +49,7 @@ static int bcache_major; static DEFINE_IDA(bcache_device_idx); static wait_queue_head_t unregister_wait; struct workqueue_struct *bcache_wq; +struct workqueue_struct *bch_flush_wq; struct workqueue_struct *bch_journal_wq;

@@ -2821,6 +2822,8 @@ static void bcache_exit(void) destroy_workqueue(bcache_wq); if (bch_journal_wq) destroy_workqueue(bch_journal_wq); + if (bch_flush_wq) + destroy_workqueue(bch_flush_wq); bch_btree_exit();

if (bcache_major) @@ -2884,6 +2887,19 @@ static int __init bcache_init(void) if (!bcache_wq) goto err;

+ /* + * Let's not make this `WQ_MEM_RECLAIM` for the following reasons: + * + * 1. It used `system_wq` before which also does no memory reclaim. + * 2. With `WQ_MEM_RECLAIM` desktop stalls, increased boot times, and + * reduced throughput can be observed. + * + * We still want to user our own queue to not congest the `system_wq`. + */ + bch_flush_wq = alloc_workqueue("bch_flush", 0, 0); + if (!bch_flush_wq) + goto err; + bch_journal_wq = alloc_workqueue("bch_journal", WQ_MEM_RECLAIM, 0); if (!bch_journal_wq) goto err;