drbd: performance - don't lose unplug events
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 3678d3d..d09aac4 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -505,7 +505,7 @@
* corresponding hlist_del is in _req_may_be_done() */
hlist_add_head(&req->colision, ar_hash_slot(mdev, req->sector));
- set_bit(UNPLUG_REMOTE, &mdev->flags); /* why? */
+ set_bit(UNPLUG_REMOTE, &mdev->flags);
D_ASSERT(req->rq_state & RQ_NET_PENDING);
req->rq_state |= RQ_NET_QUEUED;
@@ -536,6 +536,11 @@
*
* Add req to the (now) current epoch (barrier). */
+ /* otherwise we may lose an unplug, which may cause some remote
+ * io-scheduler timeout to expire, increasing maximum latency,
+ * hurting performance. */
+ set_bit(UNPLUG_REMOTE, &mdev->flags);
+
/* see drbd_make_request_common,
* just after it grabs the req_lock */
D_ASSERT(test_bit(CREATE_BARRIER, &mdev->flags) == 0);