1 files changed, 33 insertions, 0 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 541bd0d..7477f33 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -633,6 +633,28 @@ static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
 	return false;
 }
 
+static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
+		bool rw, unsigned long start)
+{
+	tg->bytes_disp[rw] = 0;
+	tg->io_disp[rw] = 0;
+
+	/*
+	 * Previous slice has expired. We must have trimmed it after last
+	 * bio dispatch. That means since start of last slice, we never used
+	 * that bandwidth. Do try to make use of that bandwidth while giving
+	 * credit.
+	 */
+	if (time_after_eq(start, tg->slice_start[rw]))
+		tg->slice_start[rw] = start;
+
+	tg->slice_end[rw] = jiffies + throtl_slice;
+	throtl_log(&tg->service_queue,
+		   "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
+		   rw == READ ? 'R' : 'W', tg->slice_start[rw],
+		   tg->slice_end[rw], jiffies);
+}
+
 static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
 {
 	tg->bytes_disp[rw] = 0;
@@ -992,6 +1014,16 @@ static void tg_update_disptime(struct throtl_grp *tg)
 	tg->flags &= ~THROTL_TG_WAS_EMPTY;
 }
 
+static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
+					struct throtl_grp *parent_tg, bool rw)
+{
+	if (throtl_slice_used(parent_tg, rw)) {
+		throtl_start_new_slice_with_credit(parent_tg, rw,
+				child_tg->slice_start[rw]);
+	}
+
+}
+
 static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
 {
 	struct throtl_service_queue *sq = &tg->service_queue;
@@ -1020,6 +1052,7 @@ static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
 	 */
 	if (parent_tg) {
 		throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
+		start_parent_slice_with_credit(tg, parent_tg, rw);
 	} else {
 		throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
 				     &parent_sq->queued[rw]);