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From: Mikulas Patocka <>
To: Mike Snitzer <>, Joe Thornber <>
Subject: [dm-devel] [PATCH] dm-writecache: back off if the kcopyd workqueue is blocked
Date: Sun, 6 Jun 2021 16:08:21 -0400 (EDT)	[thread overview]
Message-ID: <> (raw)


Does this patch help in your tests? In my tests, it improves performance 
by about 20%.

Signed-off-by: Mikulas Patocka <>

Index: linux-2.6/drivers/md/dm-kcopyd.c
--- linux-2.6.orig/drivers/md/dm-kcopyd.c
+++ linux-2.6/drivers/md/dm-kcopyd.c
@@ -896,6 +896,12 @@ void dm_kcopyd_do_callback(void *j, int
+void dm_kcopyd_wait_if_busy(struct dm_kcopyd_client *kc)
+	flush_workqueue(kc->kcopyd_wq);
  * Cancels a kcopyd job, eg. someone might be deactivating a
  * mirror.
Index: linux-2.6/drivers/md/dm-writecache.c
--- linux-2.6.orig/drivers/md/dm-writecache.c
+++ linux-2.6/drivers/md/dm-writecache.c
@@ -1815,6 +1815,9 @@ static void writecache_writeback(struct
 	struct writeback_list wbl;
 	unsigned long n_walked;
+	if (!WC_MODE_PMEM(wc))
+		dm_kcopyd_wait_if_busy(wc->dm_kcopyd);
 	if (writecache_has_error(wc)) {
Index: linux-2.6/include/linux/dm-kcopyd.h
--- linux-2.6.orig/include/linux/dm-kcopyd.h
+++ linux-2.6/include/linux/dm-kcopyd.h
@@ -82,6 +82,8 @@ void *dm_kcopyd_prepare_callback(struct
 				 dm_kcopyd_notify_fn fn, void *context);
 void dm_kcopyd_do_callback(void *job, int read_err, unsigned long write_err);
+void dm_kcopyd_wait_if_busy(struct dm_kcopyd_client *kc);
 void dm_kcopyd_zero(struct dm_kcopyd_client *kc,
 		    unsigned num_dests, struct dm_io_region *dests,
 		    unsigned flags, dm_kcopyd_notify_fn fn, void *context);

dm-devel mailing list

             reply	other threads:[~2021-06-06 20:08 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-06 20:08 Mikulas Patocka [this message]
2021-06-15 17:47 [dm-devel] [PATCH] dm-writecache: back off if the kcopyd workqueue is blocked Mikulas Patocka

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