[PATCH 0/4] blk-throttle: fix a few issues

[PATCH 0/4] blk-throttle: fix a few issues

[Shaohua Li]

Hi,

The patchset fix a few issues for io.low limit. The title of the patches
explain the issues pretty well.

Thanks,
Shaohua

Shaohua Li (4):
  blk-throttle: add hierarchy support for latency target and idle time
  blk-throttle: output some debug info in trace
  blk-throttle: respect 0 bps/iops settings for io.low
  blk-throttle: force user to configure all settings for io.low

 block/blk-throttle.c | 172 ++++++++++++++++++++++++++++++++-------------------
 1 file changed, 109 insertions(+), 63 deletions(-)

-- 
2.9.3

[PATCH 1/4] blk-throttle: add hierarchy support for latency target and idle time

[Shaohua Li]

For idle time, children's setting should not be bigger than parent's.
For latency target, children's setting should not be smaller than
parent's. The leaf nodes will adjust their settings according to the
hierarchy and compare their IO with the settings and do
upgrade/downgrade. parents nodes don't need to track their IO
latency/idle time.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 block/blk-throttle.c | 50 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 36 insertions(+), 14 deletions(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index b78db2e..16174f8 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -157,6 +157,7 @@ struct throtl_grp {
 	unsigned long last_check_time;
 
 	unsigned long latency_target; /* us */
+	unsigned long latency_target_conf; /* us */
 	/* When did we start a new slice */
 	unsigned long slice_start[2];
 	unsigned long slice_end[2];
@@ -165,6 +166,7 @@ struct throtl_grp {
 	unsigned long checked_last_finish_time; /* ns / 1024 */
 	unsigned long avg_idletime; /* ns / 1024 */
 	unsigned long idletime_threshold; /* us */
+	unsigned long idletime_threshold_conf; /* us */
 
 	unsigned int bio_cnt; /* total bios */
 	unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
@@ -482,6 +484,7 @@ static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
 	/* LIMIT_LOW will have default value 0 */
 
 	tg->latency_target = DFL_LATENCY_TARGET;
+	tg->latency_target_conf = DFL_LATENCY_TARGET;
 
 	return &tg->pd;
 }
@@ -512,6 +515,7 @@ static void throtl_pd_init(struct blkg_policy_data *pd)
 	tg->td = td;
 
 	tg->idletime_threshold = td->dft_idletime_threshold;
+	tg->idletime_threshold_conf = td->dft_idletime_threshold;
 }
 
 /*
@@ -1367,8 +1371,25 @@ static void tg_conf_updated(struct throtl_grp *tg)
 	 * restrictions in the whole hierarchy and allows them to bypass
 	 * blk-throttle.
 	 */
-	blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg))
-		tg_update_has_rules(blkg_to_tg(blkg));
+	blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg)) {
+		struct throtl_grp *this_tg = blkg_to_tg(blkg);
+		struct throtl_grp *parent_tg;
+
+		tg_update_has_rules(this_tg);
+		/* ignore root/second level */
+		if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
+		    !blkg->parent->parent)
+			continue;
+		parent_tg = blkg_to_tg(blkg->parent);
+		/*
+		 * make sure all children has lower idle time threshold and
+		 * higher latency target
+		 */
+		this_tg->idletime_threshold = min(this_tg->idletime_threshold,
+				parent_tg->idletime_threshold);
+		this_tg->latency_target = max(this_tg->latency_target,
+				parent_tg->latency_target);
+	}
 
 	/*
 	 * We're already holding queue_lock and know @tg is valid.  Let's
@@ -1497,8 +1518,8 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
 	    tg->iops_conf[READ][off] == iops_dft &&
 	    tg->iops_conf[WRITE][off] == iops_dft &&
 	    (off != LIMIT_LOW ||
-	     (tg->idletime_threshold == tg->td->dft_idletime_threshold &&
-	      tg->latency_target == DFL_LATENCY_TARGET)))
+	     (tg->idletime_threshold_conf == tg->td->dft_idletime_threshold &&
+	      tg->latency_target_conf == DFL_LATENCY_TARGET)))
 		return 0;
 
 	if (tg->bps_conf[READ][off] != bps_dft)
@@ -1514,17 +1535,17 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
 		snprintf(bufs[3], sizeof(bufs[3]), "%u",
 			tg->iops_conf[WRITE][off]);
 	if (off == LIMIT_LOW) {
-		if (tg->idletime_threshold == ULONG_MAX)
+		if (tg->idletime_threshold_conf == ULONG_MAX)
 			strcpy(idle_time, " idle=max");
 		else
 			snprintf(idle_time, sizeof(idle_time), " idle=%lu",
-				tg->idletime_threshold);
+				tg->idletime_threshold_conf);
 
-		if (tg->latency_target == ULONG_MAX)
+		if (tg->latency_target_conf == ULONG_MAX)
 			strcpy(latency_time, " latency=max");
 		else
 			snprintf(latency_time, sizeof(latency_time),
-				" latency=%lu", tg->latency_target);
+				" latency=%lu", tg->latency_target_conf);
 	}
 
 	seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n",
@@ -1563,8 +1584,8 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 	v[2] = tg->iops_conf[READ][index];
 	v[3] = tg->iops_conf[WRITE][index];
 
-	idle_time = tg->idletime_threshold;
-	latency_time = tg->latency_target;
+	idle_time = tg->idletime_threshold_conf;
+	latency_time = tg->latency_target_conf;
 	while (true) {
 		char tok[27];	/* wiops=18446744073709551616 */
 		char *p;
@@ -1628,10 +1649,10 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 		blk_throtl_update_limit_valid(tg->td);
 		if (tg->td->limit_valid[LIMIT_LOW])
 			tg->td->limit_index = LIMIT_LOW;
-		tg->idletime_threshold = (idle_time == ULONG_MAX) ?
-			ULONG_MAX : idle_time;
-		tg->latency_target = (latency_time == ULONG_MAX) ?
-			ULONG_MAX : latency_time;
+		tg->idletime_threshold_conf = idle_time;
+		tg->idletime_threshold = tg->idletime_threshold_conf;
+		tg->latency_target_conf = latency_time;
+		tg->latency_target = tg->latency_target_conf;
 	}
 	tg_conf_updated(tg);
 	ret = 0;
@@ -2385,6 +2406,7 @@ void blk_throtl_register_queue(struct request_queue *q)
 		struct throtl_grp *tg = blkg_to_tg(blkg);
 
 		tg->idletime_threshold = td->dft_idletime_threshold;
+		tg->idletime_threshold_conf = td->dft_idletime_threshold;
 	}
 	rcu_read_unlock();
 }
-- 
2.9.3

[PATCH 2/4] blk-throttle: output some debug info in trace

[Shaohua Li]

These info are important to understand what's happening and help debug.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 block/blk-throttle.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 16174f8..1f8d62f 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1748,12 +1748,18 @@ static bool throtl_tg_is_idle(struct throtl_grp *tg)
 	 * - IO latency is largely below threshold
 	 */
 	unsigned long time = jiffies_to_usecs(4 * tg->td->throtl_slice);
+	bool ret;
 
 	time = min_t(unsigned long, MAX_IDLE_TIME, time);
-	return (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
+	ret = (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
 	       tg->avg_idletime > tg->idletime_threshold ||
 	       (tg->latency_target && tg->bio_cnt &&
 		tg->bad_bio_cnt * 5 < tg->bio_cnt);
+	throtl_log(&tg->service_queue,
+		"avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
+		tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
+		tg->bio_cnt, ret, tg->td->scale);
+	return ret;
 }
 
 static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
@@ -1849,6 +1855,7 @@ static void throtl_upgrade_state(struct throtl_data *td)
 	struct cgroup_subsys_state *pos_css;
 	struct blkcg_gq *blkg;
 
+	throtl_log(&td->service_queue, "upgrade to max");
 	td->limit_index = LIMIT_MAX;
 	td->low_upgrade_time = jiffies;
 	td->scale = 0;
@@ -1871,6 +1878,7 @@ static void throtl_downgrade_state(struct throtl_data *td, int new)
 {
 	td->scale /= 2;
 
+	throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
 	if (td->scale) {
 		td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
 		return;
@@ -2044,6 +2052,11 @@ static void throtl_update_latency_buckets(struct throtl_data *td)
 		td->avg_buckets[i].valid = true;
 		last_latency = td->avg_buckets[i].latency;
 	}
+
+	for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
+		throtl_log(&td->service_queue,
+			"Latency bucket %d: latency=%ld, valid=%d", i,
+			td->avg_buckets[i].latency, td->avg_buckets[i].valid);
 }
 #else
 static inline void throtl_update_latency_buckets(struct throtl_data *td)
-- 
2.9.3

[PATCH 3/4] blk-throttle: respect 0 bps/iops settings for io.low

[Shaohua Li]

If a cgroup with low limit 0 for both bps/iops, the cgroup's low limit
is ignored and we throttle the cgroup with its max limit. In this way,
other cgroups with a low limit will not get protected. To fix this, we
don't do the exception any more. cgroup will be throttled to a limit 0
if it uese default setting. To avoid completed stall, we give such
cgroup tiny IO resources.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 block/blk-throttle.c | 41 +++++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 1f8d62f..f6a9f42a 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -27,6 +27,8 @@ static int throtl_quantum = 32;
 #define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
 /* default latency target is 0, eg, guarantee IO latency by default */
 #define DFL_LATENCY_TARGET (0)
+#define MIN_THROTL_BPS (320 * 1024)
+#define MIN_THROTL_IOPS (10)
 
 #define SKIP_LATENCY (((u64)1) << BLK_STAT_RES_SHIFT)
 
@@ -296,8 +298,14 @@ static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
 
 	td = tg->td;
 	ret = tg->bps[rw][td->limit_index];
-	if (ret == 0 && td->limit_index == LIMIT_LOW)
-		return tg->bps[rw][LIMIT_MAX];
+	if (ret == 0 && td->limit_index == LIMIT_LOW) {
+		/* intermediate node or iops isn't 0 */
+		if (!list_empty(&blkg->blkcg->css.children) ||
+		    tg->iops[rw][td->limit_index])
+			return U64_MAX;
+		else
+			return MIN_THROTL_BPS;
+	}
 
 	if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
 	    tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
@@ -317,10 +325,17 @@ static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
 
 	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
 		return UINT_MAX;
+
 	td = tg->td;
 	ret = tg->iops[rw][td->limit_index];
-	if (ret == 0 && tg->td->limit_index == LIMIT_LOW)
-		return tg->iops[rw][LIMIT_MAX];
+	if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
+		/* intermediate node or bps isn't 0 */
+		if (!list_empty(&blkg->blkcg->css.children) ||
+		    tg->bps[rw][td->limit_index])
+			return UINT_MAX;
+		else
+			return MIN_THROTL_IOPS;
+	}
 
 	if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
 	    tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
@@ -1353,7 +1368,7 @@ static int tg_print_conf_uint(struct seq_file *sf, void *v)
 	return 0;
 }
 
-static void tg_conf_updated(struct throtl_grp *tg)
+static void tg_conf_updated(struct throtl_grp *tg, bool global)
 {
 	struct throtl_service_queue *sq = &tg->service_queue;
 	struct cgroup_subsys_state *pos_css;
@@ -1371,7 +1386,8 @@ static void tg_conf_updated(struct throtl_grp *tg)
 	 * restrictions in the whole hierarchy and allows them to bypass
 	 * blk-throttle.
 	 */
-	blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg)) {
+	blkg_for_each_descendant_pre(blkg, pos_css,
+			global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
 		struct throtl_grp *this_tg = blkg_to_tg(blkg);
 		struct throtl_grp *parent_tg;
 
@@ -1434,7 +1450,7 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of,
 	else
 		*(unsigned int *)((void *)tg + of_cft(of)->private) = v;
 
-	tg_conf_updated(tg);
+	tg_conf_updated(tg, false);
 	ret = 0;
 out_finish:
 	blkg_conf_finish(&ctx);
@@ -1522,16 +1538,16 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
 	      tg->latency_target_conf == DFL_LATENCY_TARGET)))
 		return 0;
 
-	if (tg->bps_conf[READ][off] != bps_dft)
+	if (tg->bps_conf[READ][off] != U64_MAX)
 		snprintf(bufs[0], sizeof(bufs[0]), "%llu",
 			tg->bps_conf[READ][off]);
-	if (tg->bps_conf[WRITE][off] != bps_dft)
+	if (tg->bps_conf[WRITE][off] != U64_MAX)
 		snprintf(bufs[1], sizeof(bufs[1]), "%llu",
 			tg->bps_conf[WRITE][off]);
-	if (tg->iops_conf[READ][off] != iops_dft)
+	if (tg->iops_conf[READ][off] != UINT_MAX)
 		snprintf(bufs[2], sizeof(bufs[2]), "%u",
 			tg->iops_conf[READ][off]);
-	if (tg->iops_conf[WRITE][off] != iops_dft)
+	if (tg->iops_conf[WRITE][off] != UINT_MAX)
 		snprintf(bufs[3], sizeof(bufs[3]), "%u",
 			tg->iops_conf[WRITE][off]);
 	if (off == LIMIT_LOW) {
@@ -1654,7 +1670,8 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 		tg->latency_target_conf = latency_time;
 		tg->latency_target = tg->latency_target_conf;
 	}
-	tg_conf_updated(tg);
+	tg_conf_updated(tg, index == LIMIT_LOW &&
+		tg->td->limit_valid[LIMIT_LOW]);
 	ret = 0;
 out_finish:
 	blkg_conf_finish(&ctx);
-- 
2.9.3

[PATCH 4/4] blk-throttle: force user to configure all settings for io.low

[Shaohua Li]

Default value of io.low limit is 0. If user doesn't configure the limit,
last patch makes cgroup be throttled to very tiny bps/iops, which could
stall the system. A cgroup with default settings of io.low limit really
means nothing, so we force user to configure all settings, otherwise
io.low limit doesn't take effect. With this stragety, default setting of
latency/idle isn't important, so just set them to very conservative and
safe value.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 block/blk-throttle.c | 80 ++++++++++++++++++++++++----------------------------
 1 file changed, 37 insertions(+), 43 deletions(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f6a9f42a..fc13dd0 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -22,13 +22,11 @@ static int throtl_quantum = 32;
 #define DFL_THROTL_SLICE_HD (HZ / 10)
 #define DFL_THROTL_SLICE_SSD (HZ / 50)
 #define MAX_THROTL_SLICE (HZ)
-#define DFL_IDLE_THRESHOLD_SSD (1000L) /* 1 ms */
-#define DFL_IDLE_THRESHOLD_HD (100L * 1000) /* 100 ms */
 #define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
-/* default latency target is 0, eg, guarantee IO latency by default */
-#define DFL_LATENCY_TARGET (0)
 #define MIN_THROTL_BPS (320 * 1024)
 #define MIN_THROTL_IOPS (10)
+#define DFL_LATENCY_TARGET (-1L)
+#define DFL_IDLE_THRESHOLD (0)
 
 #define SKIP_LATENCY (((u64)1) << BLK_STAT_RES_SHIFT)
 
@@ -205,8 +203,6 @@ struct throtl_data
 	unsigned int limit_index;
 	bool limit_valid[LIMIT_CNT];
 
-	unsigned long dft_idletime_threshold; /* us */
-
 	unsigned long low_upgrade_time;
 	unsigned long low_downgrade_time;
 
@@ -500,6 +496,8 @@ static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
 
 	tg->latency_target = DFL_LATENCY_TARGET;
 	tg->latency_target_conf = DFL_LATENCY_TARGET;
+	tg->idletime_threshold = DFL_IDLE_THRESHOLD;
+	tg->idletime_threshold_conf = DFL_IDLE_THRESHOLD;
 
 	return &tg->pd;
 }
@@ -528,9 +526,6 @@ static void throtl_pd_init(struct blkg_policy_data *pd)
 	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
 		sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
 	tg->td = td;
-
-	tg->idletime_threshold = td->dft_idletime_threshold;
-	tg->idletime_threshold_conf = td->dft_idletime_threshold;
 }
 
 /*
@@ -1534,7 +1529,7 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
 	    tg->iops_conf[READ][off] == iops_dft &&
 	    tg->iops_conf[WRITE][off] == iops_dft &&
 	    (off != LIMIT_LOW ||
-	     (tg->idletime_threshold_conf == tg->td->dft_idletime_threshold &&
+	     (tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD &&
 	      tg->latency_target_conf == DFL_LATENCY_TARGET)))
 		return 0;
 
@@ -1660,16 +1655,31 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 		tg->iops_conf[READ][LIMIT_MAX]);
 	tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
 		tg->iops_conf[WRITE][LIMIT_MAX]);
-
-	if (index == LIMIT_LOW) {
-		blk_throtl_update_limit_valid(tg->td);
-		if (tg->td->limit_valid[LIMIT_LOW])
-			tg->td->limit_index = LIMIT_LOW;
-		tg->idletime_threshold_conf = idle_time;
+	tg->idletime_threshold_conf = idle_time;
+	tg->latency_target_conf = latency_time;
+
+	/* force user to configure all settings for low limit  */
+	if (!(tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW] ||
+	      tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) ||
+	    tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD ||
+	    tg->latency_target_conf == DFL_LATENCY_TARGET) {
+		tg->bps[READ][LIMIT_LOW] = 0;
+		tg->bps[WRITE][LIMIT_LOW] = 0;
+		tg->iops[READ][LIMIT_LOW] = 0;
+		tg->iops[WRITE][LIMIT_LOW] = 0;
+		tg->idletime_threshold = DFL_IDLE_THRESHOLD;
+		tg->latency_target = DFL_LATENCY_TARGET;
+	} else if (index == LIMIT_LOW) {
 		tg->idletime_threshold = tg->idletime_threshold_conf;
-		tg->latency_target_conf = latency_time;
 		tg->latency_target = tg->latency_target_conf;
 	}
+
+	blk_throtl_update_limit_valid(tg->td);
+	if (tg->td->limit_valid[LIMIT_LOW]) {
+		if (index == LIMIT_LOW)
+			tg->td->limit_index = LIMIT_LOW;
+	} else
+		tg->td->limit_index = LIMIT_MAX;
 	tg_conf_updated(tg, index == LIMIT_LOW &&
 		tg->td->limit_valid[LIMIT_LOW]);
 	ret = 0;
@@ -1760,17 +1770,19 @@ static bool throtl_tg_is_idle(struct throtl_grp *tg)
 	/*
 	 * cgroup is idle if:
 	 * - single idle is too long, longer than a fixed value (in case user
-	 *   configure a too big threshold) or 4 times of slice
+	 *   configure a too big threshold) or 4 times of idletime threshold
 	 * - average think time is more than threshold
 	 * - IO latency is largely below threshold
 	 */
-	unsigned long time = jiffies_to_usecs(4 * tg->td->throtl_slice);
+	unsigned long time;
 	bool ret;
 
-	time = min_t(unsigned long, MAX_IDLE_TIME, time);
-	ret = (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
-	       tg->avg_idletime > tg->idletime_threshold ||
-	       (tg->latency_target && tg->bio_cnt &&
+	time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
+	ret = tg->latency_target == DFL_LATENCY_TARGET ||
+	      tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
+	      (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
+	      tg->avg_idletime > tg->idletime_threshold ||
+	      (tg->latency_target && tg->bio_cnt &&
 		tg->bad_bio_cnt * 5 < tg->bio_cnt);
 	throtl_log(&tg->service_queue,
 		"avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
@@ -2405,19 +2417,14 @@ void blk_throtl_exit(struct request_queue *q)
 void blk_throtl_register_queue(struct request_queue *q)
 {
 	struct throtl_data *td;
-	struct cgroup_subsys_state *pos_css;
-	struct blkcg_gq *blkg;
 
 	td = q->td;
 	BUG_ON(!td);
 
-	if (blk_queue_nonrot(q)) {
+	if (blk_queue_nonrot(q))
 		td->throtl_slice = DFL_THROTL_SLICE_SSD;
-		td->dft_idletime_threshold = DFL_IDLE_THRESHOLD_SSD;
-	} else {
+	else
 		td->throtl_slice = DFL_THROTL_SLICE_HD;
-		td->dft_idletime_threshold = DFL_IDLE_THRESHOLD_HD;
-	}
 #ifndef CONFIG_BLK_DEV_THROTTLING_LOW
 	/* if no low limit, use previous default */
 	td->throtl_slice = DFL_THROTL_SLICE_HD;
@@ -2426,19 +2433,6 @@ void blk_throtl_register_queue(struct request_queue *q)
 	td->track_bio_latency = !q->mq_ops && !q->request_fn;
 	if (!td->track_bio_latency)
 		blk_stat_enable_accounting(q);
-
-	/*
-	 * some tg are created before queue is fully initialized, eg, nonrot
-	 * isn't initialized yet
-	 */
-	rcu_read_lock();
-	blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {
-		struct throtl_grp *tg = blkg_to_tg(blkg);
-
-		tg->idletime_threshold = td->dft_idletime_threshold;
-		tg->idletime_threshold_conf = td->dft_idletime_threshold;
-	}
-	rcu_read_unlock();
 }
 
 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
-- 
2.9.3

Re: [PATCH 0/4] blk-throttle: fix a few issues

[Tejun Heo]

On Wed, May 17, 2017 at 01:07:23PM -0700, Shaohua Li wrote:
> Hi,
> 
> The patchset fix a few issues for io.low limit. The title of the patches
> explain the issues pretty well.

Looks good to me.

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: [PATCH 0/4] blk-throttle: fix a few issues

[Jens Axboe]

On 05/17/2017 02:07 PM, Shaohua Li wrote:
> Hi,
> 
> The patchset fix a few issues for io.low limit. The title of the patches
> explain the issues pretty well.

Looks good to me, added for 4.12-rc3.

-- 
Jens Axboe