dm cache: tune migration throttling

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 <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 6feaba24fcac800e72cb50ad87df4a26a37bc4bd..c3c18527da392d000132efc8630d56c2bee04dca 100644 (file)
--- 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)
 {