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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 03/20] Revert "bcache: Kill btree_io_wq"
Date: Wed, 10 Feb 2021 13:07:25 +0800
Message-ID: <20210210050742.31237-4-colyli@suse.de> (raw)
In-Reply-To: <20210210050742.31237-1-colyli@suse.de>

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;
-- 
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 ` Coly Li [this message]
2021-02-10  5:07 ` [PATCH 04/20] bcache: Give btree_io_wq correct semantics again Coly Li
2021-02-10  5:07 ` [PATCH 05/20] bcache: Move journal work to new flush wq Coly Li
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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