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From: Coly Li <colyli@suse.de>
To: axboe@kernel.dk
Cc: linux-bcache@vger.kernel.org, linux-block@vger.kernel.org,
	Kai Krakow <kai@kaishome.de>, Coly Li <colyli@suse.de>,
	stable@vger.kernel.org
Subject: [PATCH 05/20] bcache: Move journal work to new flush wq
Date: Wed, 10 Feb 2021 13:07:27 +0800
Message-ID: <20210210050742.31237-6-colyli@suse.de> (raw)
In-Reply-To: <20210210050742.31237-1-colyli@suse.de>

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;
-- 
2.26.2


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-10  5:07 [PATCH 00/20] bcache patches for Linux v5.12 Coly Li
2021-02-10  5:07 ` [PATCH 01/20] bcache: consider the fragmentation when update the writeback rate Coly Li
2021-02-10  5:07 ` [PATCH 02/20] bcache: Fix register_device_aync typo Coly Li
2021-02-10  5:07 ` [PATCH 03/20] Revert "bcache: Kill btree_io_wq" Coly Li
2021-02-10  5:07 ` [PATCH 04/20] bcache: Give btree_io_wq correct semantics again Coly Li
2021-02-10  5:07 ` Coly Li [this message]
2021-02-10  5:07 ` [PATCH 06/20] bcache: Avoid comma separated statements Coly Li
2021-02-10  5:07 ` [PATCH 07/20] bcache: add initial data structures for nvm pages Coly Li
2021-02-10 15:09   ` Jens Axboe
2021-02-11  3:58     ` Coly Li
2021-02-10  5:07 ` [PATCH 08/20] bcache: initialize the nvm pages allocator Coly Li
2021-02-10  5:07 ` [PATCH 09/20] bcache: initialization of the buddy Coly Li
2021-02-10  5:07 ` [PATCH 10/20] bcache: bch_nvm_alloc_pages() " Coly Li
2021-02-10  5:07 ` [PATCH 11/20] bcache: bch_nvm_free_pages() " Coly Li
2021-02-10  5:07 ` [PATCH 12/20] bcache: get allocated pages from specific owner Coly Li
2021-02-10  5:07 ` [PATCH 13/20] bcache: persist owner info when alloc/free pages Coly Li
2021-02-10  5:07 ` [PATCH 14/20] bcache: use bucket index for SET_GC_MARK() in bch_btree_gc_finish() Coly Li
2021-02-10  5:07 ` [PATCH 15/20] bcache: add BCH_FEATURE_INCOMPAT_NVDIMM_META into incompat feature set Coly Li
2021-02-10  5:07 ` [PATCH 16/20] bcache: initialize bcache journal for NVDIMM meta device Coly Li
2021-02-10  5:07 ` [PATCH 17/20] bcache: support storing bcache journal into " Coly Li
2021-02-18 21:21   ` Nix
2021-02-10  5:07 ` [PATCH 18/20] bcache: read jset from NVDIMM pages for journal replay Coly Li
2021-02-10  5:07 ` [PATCH 19/20] bcache: add sysfs interface register_nvdimm_meta to register NVDIMM meta device Coly Li
2021-02-10  5:07 ` [PATCH 20/20] bcache: only initialize nvm-pages allocator when CONFIG_BCACHE_NVM_PAGES configured Coly Li
2021-02-10 15:11 ` [PATCH 00/20] bcache patches for Linux v5.12 Jens Axboe
2021-02-12 16:09   ` Coly Li

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