From: Kai Krakow <kai@xxxxxxxxxxx>
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@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 5.4+
Signed-off-by: Kai Krakow <kai@xxxxxxxxxxx>
Signed-off-by: Coly Li <colyli@xxxxxxx>
---
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;
--
2.26.2
