[V5,13/17] blk-throttle: ignore idle cgroup limit

Commit Message

Shaohua Li Dec. 15, 2016, 8:33 p.m. UTC

Last patch introduces a way to detect idle cgroup. We use it to make
upgrade/downgrade decision. And the new algorithm can detect completely
idle cgroup too, so we can delete the corresponding code.

Signed-off-by: Shaohua Li <[e-mail]>
---
 block/blk-throttle.c | 40 ++++++++++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 14 deletions(-)

Comments

Tejun Heo Jan. 9, 2017, 9:01 p.m. UTC | #1

On Thu, Dec 15, 2016 at 12:33:04PM -0800, Shaohua Li wrote:
> Last patch introduces a way to detect idle cgroup. We use it to make
> upgrade/downgrade decision. And the new algorithm can detect completely
> idle cgroup too, so we can delete the corresponding code.

Ah, okay, the slice based idle detection gets completely removed here.
Might be better to not add it in the first place but no biggie either
way.

Thanks.

Patch

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 0218ff9..62fe72ea 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -151,8 +151,6 @@  struct throtl_grp {
 
 	unsigned long last_check_time;
 
-	unsigned long last_dispatch_time[2];
-
 	/* When did we start a new slice */
 	unsigned long slice_start[2];
 	unsigned long slice_end[2];
@@ -495,8 +493,6 @@  static void throtl_pd_online(struct blkg_policy_data *pd)
 	 * Update has_rules[] after a new group is brought online.
 	 */
 	tg_update_has_rules(tg);
-	tg->last_dispatch_time[READ] = jiffies;
-	tg->last_dispatch_time[WRITE] = jiffies;
 }
 
 static void blk_throtl_update_valid_limit(struct throtl_data *td)
@@ -1669,9 +1665,8 @@  static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
 		return true;
 
 	if (time_after_eq(jiffies,
-	     tg->last_dispatch_time[READ] + tg->td->throtl_slice) &&
-	    time_after_eq(jiffies,
-	     tg->last_dispatch_time[WRITE] + tg->td->throtl_slice))
+		tg_last_low_overflow_time(tg) + tg->td->throtl_slice) &&
+	    throtl_tg_is_idle(tg))
 		return true;
 	return false;
 }
@@ -1718,6 +1713,26 @@  static bool throtl_can_upgrade(struct throtl_data *td,
 	return true;
 }
 
+static void throtl_upgrade_check(struct throtl_grp *tg)
+{
+	unsigned long now = jiffies;
+
+	if (tg->td->limit_index != LIMIT_LOW)
+		return;
+
+	if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
+		return;
+
+	tg->last_check_time = now;
+
+	if (!time_after_eq(now,
+	     __tg_last_low_overflow_time(tg) + tg->td->throtl_slice))
+		return;
+
+	if (throtl_can_upgrade(tg->td, NULL))
+		throtl_upgrade_state(tg->td);
+}
+
 static void throtl_upgrade_state(struct throtl_data *td)
 {
 	struct cgroup_subsys_state *pos_css;
@@ -1759,18 +1774,15 @@  static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
 	struct throtl_data *td = tg->td;
 	unsigned long now = jiffies;
 
-	if (time_after_eq(now, tg->last_dispatch_time[READ] +
-					td->throtl_slice) &&
-	    time_after_eq(now, tg->last_dispatch_time[WRITE] +
-					td->throtl_slice))
-		return false;
 	/*
 	 * If cgroup is below low limit, consider downgrade and throttle other
 	 * cgroups
 	 */
 	if (time_after_eq(now, td->low_upgrade_time + td->throtl_slice) &&
 	    time_after_eq(now, tg_last_low_overflow_time(tg) +
-					td->throtl_slice))
+					td->throtl_slice) &&
+	    (!throtl_tg_is_idle(tg) ||
+	     !list_empty(&tg_to_blkg(tg)->blkcg->css.children)))
 		return true;
 	return false;
 }
@@ -1904,10 +1916,10 @@  bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
 
 again:
 	while (true) {
-		tg->last_dispatch_time[rw] = jiffies;
 		if (tg->last_low_overflow_time[rw] == 0)
 			tg->last_low_overflow_time[rw] = jiffies;
 		throtl_downgrade_check(tg);
+		throtl_upgrade_check(tg);
 		/* throtl is FIFO - if bios are already queued, should queue */
 		if (sq->nr_queued[rw])
 			break;