[PATCH 1/3] dm raid1: add resync speed control for dm-raid1

[Guangliang Zhao <gzhao@suse.com>]

The IO Performance on the already available lv is very bad
during the initial sync when we create a mirror lv. This
patch add the rate limit for every mirror target to control
resync speed.

Signed-off-by: Guangliang Zhao <gzhao@suse.com>
---
 drivers/md/dm-raid1.c |   30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 9bfd057..fb87779 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -13,6 +13,7 @@
 #include <linux/pagemap.h>
 #include <linux/slab.h>
 #include <linux/workqueue.h>
+#include <linux/ratelimit.h>
 #include <linux/device-mapper.h>
 #include <linux/dm-io.h>
 #include <linux/dm-dirty-log.h>
@@ -26,6 +27,11 @@
 #define DM_RAID1_HANDLE_ERRORS 0x01
 #define errors_handled(p)	((p)->features & DM_RAID1_HANDLE_ERRORS)
 
+/* Default resync interval*/
+#define RESYNC_JIFFIES	HZ
+/* Default max resync speed in KB/s */
+#define DEFAULT_RESYNC_SPEED		(100 << 10)
+
 static DECLARE_WAIT_QUEUE_HEAD(_kmirrord_recovery_stopped);
 
 /*-----------------------------------------------------------------
@@ -69,6 +75,9 @@ struct mirror_set {
 	int log_failure;
 	int leg_failure;
 	atomic_t suspend;
+	/* recovery speed control */
+	struct ratelimit_state ms_rlimit;
+	struct delayed_work resync_waker;
 
 	atomic_t default_mirror;	/* Default mirror */
 
@@ -383,12 +392,18 @@ static void do_recovery(struct mirror_set *ms)
 	/*
 	 * Copy any already quiesced regions.
 	 */
-	while ((reg = dm_rh_recovery_start(ms->rh))) {
+	while (__ratelimit(&ms->ms_rlimit) &&
+			(reg = dm_rh_recovery_start(ms->rh))) {
 		r = recover(ms, reg);
 		if (r)
 			dm_rh_recovery_end(reg, 0);
 	}
 
+	/* Broke off the resync process, so wake up kmirrord later on */
+	if (!ms->in_sync)
+		schedule_delayed_work(&ms->resync_waker,
+				      ms->ms_rlimit.interval);
+
 	/*
 	 * Update the in sync flag.
 	 */
@@ -842,6 +857,14 @@ static void do_mirror(struct work_struct *work)
 	do_failures(ms, &failures);
 }
 
+static void do_resync_wake(struct work_struct *work)
+{
+	struct mirror_set *ms =
+		container_of(work, struct mirror_set, resync_waker.work);
+
+	wakeup_mirrord(ms);
+}
+
 /*-----------------------------------------------------------------
  * Target functions
  *---------------------------------------------------------------*/
@@ -852,6 +875,7 @@ static struct mirror_set *alloc_context(unsigned int nr_mirrors,
 {
 	size_t len;
 	struct mirror_set *ms = NULL;
+	int burst;
 
 	len = sizeof(*ms) + (sizeof(ms->mirror[0]) * nr_mirrors);
 
@@ -875,6 +899,10 @@ static struct mirror_set *alloc_context(unsigned int nr_mirrors,
 	ms->leg_failure = 0;
 	atomic_set(&ms->suspend, 0);
 	atomic_set(&ms->default_mirror, DEFAULT_MIRROR);
+	burst = (DEFAULT_RESYNC_SPEED * (RESYNC_JIFFIES / HZ)) << 1;
+	burst = DIV_ROUND_UP(burst, region_size);
+	ratelimit_state_init(&ms->ms_rlimit, RESYNC_JIFFIES, burst);
+	INIT_DELAYED_WORK(&ms->resync_waker, do_resync_wake);
 
 	ms->read_record_pool = mempool_create_slab_pool(MIN_READ_RECORDS,
 						_dm_raid1_read_record_cache);
-- 
1.7.10.4