dm cache: tune migration throttling

jthornber · kergon · commit f8350daf7af0 · 2013-05-10T14:37:16.000+01:00
Tune the dm cache migration throttling.

i) Issue a tick every second, just in case there's no i/o going through.

ii) Drop the migration threshold right down to something suitable for
background work.

Signed-off-by: Joe Thornber &lt;ejt@redhat.com&gt;
Signed-off-by: Alasdair G Kergon &lt;agk@redhat.com&gt;
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
@@ -1445,6 +1445,7 @@ static void do_worker(struct work_struct *ws)
 static void do_waker(struct work_struct *ws)
 {
 	struct cache *cache = container_of(to_delayed_work(ws), struct cache, waker);
+	policy_tick(cache->policy);
 	wake_worker(cache);
 	queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD);
 }
@@ -1886,7 +1887,7 @@ static sector_t calculate_discard_block_size(sector_t cache_block_size,
 	return discard_block_size;
 }
 
-#define DEFAULT_MIGRATION_THRESHOLD (2048 * 100)
+#define DEFAULT_MIGRATION_THRESHOLD 2048
 
 static int cache_create(struct cache_args *ca, struct cache **result)
 {

Original file line number	Diff line number	Diff line change
`@@ -1445,6 +1445,7 @@ static void do_worker(struct work_struct *ws)`
`1445`	`1445`	`static void do_waker(struct work_struct *ws)`
`1446`	`1446`	`{`
`1447`	`1447`	`struct cache *cache = container_of(to_delayed_work(ws), struct cache, waker);`
	`1448`	`+ policy_tick(cache->policy);`
`1448`	`1449`	`wake_worker(cache);`
`1449`	`1450`	`queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD);`
`1450`	`1451`	`}`
`@@ -1886,7 +1887,7 @@ static sector_t calculate_discard_block_size(sector_t cache_block_size,`
`1886`	`1887`	`return discard_block_size;`
`1887`	`1888`	`}`
`1888`	`1889`
`1889`		`-#define DEFAULT_MIGRATION_THRESHOLD (2048 * 100)`
	`1890`	`+#define DEFAULT_MIGRATION_THRESHOLD 2048`
`1890`	`1891`
`1891`	`1892`	`static int cache_create(struct cache_args ca, struct cache *result)`
`1892`	`1893`	`{`