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Date: Sat, 14 Jan 2017 19:42:23 -0800
From: Shaohua Li <shli@...com>
To: <linux-kernel@...r.kernel.org>, <linux-block@...r.kernel.org>
CC: <Kernel-team@...com>, <tj@...nel.org>, <axboe@...com>,
<vgoyal@...hat.com>
Subject: [PATCH V6 06/18] blk-throttle: add downgrade logic
When queue state machine is in LIMIT_MAX state, but a cgroup is below
its low limit for some time, the queue should be downgraded to lower
state as one cgroup's low limit isn't met.
Signed-off-by: Shaohua Li <shli@...com>
---
block/blk-throttle.c | 156 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 156 insertions(+)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 4cc066f..9dbbc94d 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -140,6 +140,13 @@ struct throtl_grp {
/* Number of bio's dispatched in current slice */
unsigned int io_disp[2];
+ unsigned long last_low_overflow_time[2];
+
+ uint64_t last_bytes_disp[2];
+ unsigned int last_io_disp[2];
+
+ unsigned long last_check_time;
+
/* When did we start a new slice */
unsigned long slice_start[2];
unsigned long slice_end[2];
@@ -159,6 +166,9 @@ struct throtl_data
struct work_struct dispatch_work;
unsigned int limit_index;
bool limit_valid[LIMIT_CNT];
+
+ unsigned long low_upgrade_time;
+ unsigned long low_downgrade_time;
};
static void throtl_pending_timer_fn(unsigned long arg);
@@ -898,6 +908,8 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
/* Charge the bio to the group */
tg->bytes_disp[rw] += bio->bi_iter.bi_size;
tg->io_disp[rw]++;
+ tg->last_bytes_disp[rw] += bio->bi_iter.bi_size;
+ tg->last_io_disp[rw]++;
/*
* BIO_THROTTLED is used to prevent the same bio to be throttled
@@ -1523,6 +1535,45 @@ static struct blkcg_policy blkcg_policy_throtl = {
.pd_free_fn = throtl_pd_free,
};
+static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
+{
+ unsigned long rtime = jiffies, wtime = jiffies;
+
+ if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
+ rtime = tg->last_low_overflow_time[READ];
+ if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
+ wtime = tg->last_low_overflow_time[WRITE];
+ return min(rtime, wtime);
+}
+
+/* tg should not be an intermediate node */
+static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
+{
+ struct throtl_service_queue *parent_sq;
+ struct throtl_grp *parent = tg;
+ unsigned long ret = __tg_last_low_overflow_time(tg);
+
+ while (true) {
+ parent_sq = parent->service_queue.parent_sq;
+ parent = sq_to_tg(parent_sq);
+ if (!parent)
+ break;
+
+ /*
+ * The parent doesn't have low limit, it always reaches low
+ * limit. Its overflow time is useless for children
+ */
+ if (!parent->bps[READ][LIMIT_LOW] &&
+ !parent->iops[READ][LIMIT_LOW] &&
+ !parent->bps[WRITE][LIMIT_LOW] &&
+ !parent->iops[WRITE][LIMIT_LOW])
+ continue;
+ if (time_after(__tg_last_low_overflow_time(parent), ret))
+ ret = __tg_last_low_overflow_time(parent);
+ }
+ return ret;
+}
+
static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
{
struct throtl_service_queue *sq = &tg->service_queue;
@@ -1566,6 +1617,9 @@ static bool throtl_can_upgrade(struct throtl_data *td,
if (td->limit_index != LIMIT_LOW)
return false;
+ if (time_before(jiffies, td->low_downgrade_time + throtl_slice))
+ return false;
+
rcu_read_lock();
blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
struct throtl_grp *tg = blkg_to_tg(blkg);
@@ -1589,6 +1643,7 @@ static void throtl_upgrade_state(struct throtl_data *td)
struct blkcg_gq *blkg;
td->limit_index = LIMIT_MAX;
+ td->low_upgrade_time = jiffies;
rcu_read_lock();
blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
struct throtl_grp *tg = blkg_to_tg(blkg);
@@ -1604,6 +1659,99 @@ static void throtl_upgrade_state(struct throtl_data *td)
queue_work(kthrotld_workqueue, &td->dispatch_work);
}
+static void throtl_downgrade_state(struct throtl_data *td, int new)
+{
+ td->limit_index = new;
+ td->low_downgrade_time = jiffies;
+}
+
+static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
+{
+ struct throtl_data *td = tg->td;
+ unsigned long now = jiffies;
+
+ /*
+ * If cgroup is below low limit, consider downgrade and throttle other
+ * cgroups
+ */
+ if (time_after_eq(now, td->low_upgrade_time + throtl_slice) &&
+ time_after_eq(now, tg_last_low_overflow_time(tg) + throtl_slice))
+ return true;
+ return false;
+}
+
+static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
+{
+ while (true) {
+ if (!throtl_tg_can_downgrade(tg))
+ return false;
+ tg = sq_to_tg(tg->service_queue.parent_sq);
+ if (!tg || !tg_to_blkg(tg)->parent)
+ break;
+ }
+ return true;
+}
+
+static void throtl_downgrade_check(struct throtl_grp *tg)
+{
+ uint64_t bps;
+ unsigned int iops;
+ unsigned long elapsed_time;
+ unsigned long now = jiffies;
+
+ if (tg->td->limit_index != LIMIT_MAX ||
+ !tg->td->limit_valid[LIMIT_LOW])
+ return;
+ if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
+ return;
+ if (time_after(tg->last_check_time + throtl_slice, now))
+ return;
+
+ elapsed_time = now - tg->last_check_time;
+ tg->last_check_time = now;
+
+ if (time_before(now, tg_last_low_overflow_time(tg) + throtl_slice))
+ return;
+
+ if (tg->bps[READ][LIMIT_LOW]) {
+ bps = tg->last_bytes_disp[READ] * HZ;
+ do_div(bps, elapsed_time);
+ if (bps >= tg->bps[READ][LIMIT_LOW])
+ tg->last_low_overflow_time[READ] = now;
+ }
+
+ if (tg->bps[WRITE][LIMIT_LOW]) {
+ bps = tg->last_bytes_disp[WRITE] * HZ;
+ do_div(bps, elapsed_time);
+ if (bps >= tg->bps[WRITE][LIMIT_LOW])
+ tg->last_low_overflow_time[WRITE] = now;
+ }
+
+ if (tg->iops[READ][LIMIT_LOW]) {
+ iops = tg->last_io_disp[READ] * HZ / elapsed_time;
+ if (iops >= tg->iops[READ][LIMIT_LOW])
+ tg->last_low_overflow_time[READ] = now;
+ }
+
+ if (tg->iops[WRITE][LIMIT_LOW]) {
+ iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
+ if (iops >= tg->iops[WRITE][LIMIT_LOW])
+ tg->last_low_overflow_time[WRITE] = now;
+ }
+
+ /*
+ * If cgroup is below low limit, consider downgrade and throttle other
+ * cgroups
+ */
+ if (throtl_hierarchy_can_downgrade(tg))
+ throtl_downgrade_state(tg->td, LIMIT_LOW);
+
+ tg->last_bytes_disp[READ] = 0;
+ tg->last_bytes_disp[WRITE] = 0;
+ tg->last_io_disp[READ] = 0;
+ tg->last_io_disp[WRITE] = 0;
+}
+
bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
struct bio *bio)
{
@@ -1628,12 +1776,16 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
again:
while (true) {
+ if (tg->last_low_overflow_time[rw] == 0)
+ tg->last_low_overflow_time[rw] = jiffies;
+ throtl_downgrade_check(tg);
/* throtl is FIFO - if bios are already queued, should queue */
if (sq->nr_queued[rw])
break;
/* if above limits, break to queue */
if (!tg_may_dispatch(tg, bio, NULL)) {
+ tg->last_low_overflow_time[rw] = jiffies;
if (throtl_can_upgrade(tg->td, tg)) {
throtl_upgrade_state(tg->td);
goto again;
@@ -1677,6 +1829,8 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
tg->io_disp[rw], tg_iops_limit(tg, rw),
sq->nr_queued[READ], sq->nr_queued[WRITE]);
+ tg->last_low_overflow_time[rw] = jiffies;
+
bio_associate_current(bio);
tg->td->nr_queued[rw]++;
throtl_add_bio_tg(bio, qn, tg);
@@ -1787,6 +1941,8 @@ int blk_throtl_init(struct request_queue *q)
td->limit_valid[LIMIT_MAX] = true;
td->limit_index = LIMIT_MAX;
+ td->low_upgrade_time = jiffies;
+ td->low_downgrade_time = jiffies;
/* activate policy */
ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
if (ret)
--
2.9.3
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