summaryrefslogtreecommitdiffstats
path: root/block/blk-throttle.c
diff options
context:
space:
mode:
Diffstat (limited to 'block/blk-throttle.c')
-rw-r--r--block/blk-throttle.c57
1 files changed, 54 insertions, 3 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 014b2e96a423..62984fc92015 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -175,6 +175,8 @@ struct throtl_data
unsigned long low_upgrade_time;
unsigned long low_downgrade_time;
+
+ unsigned int scale;
};
static void throtl_pending_timer_fn(unsigned long arg);
@@ -226,29 +228,70 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
return container_of(sq, struct throtl_data, service_queue);
}
+/*
+ * cgroup's limit in LIMIT_MAX is scaled if low limit is set. This scale is to
+ * make the IO dispatch more smooth.
+ * Scale up: linearly scale up according to lapsed time since upgrade. For
+ * every throtl_slice, the limit scales up 1/2 .low limit till the
+ * limit hits .max limit
+ * Scale down: exponentially scale down if a cgroup doesn't hit its .low limit
+ */
+static uint64_t throtl_adjusted_limit(uint64_t low, struct throtl_data *td)
+{
+ /* arbitrary value to avoid too big scale */
+ if (td->scale < 4096 && time_after_eq(jiffies,
+ td->low_upgrade_time + td->scale * td->throtl_slice))
+ td->scale = (jiffies - td->low_upgrade_time) / td->throtl_slice;
+
+ return low + (low >> 1) * td->scale;
+}
+
static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
{
struct blkcg_gq *blkg = tg_to_blkg(tg);
+ struct throtl_data *td;
uint64_t ret;
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
return U64_MAX;
- ret = tg->bps[rw][tg->td->limit_index];
- if (ret == 0 && tg->td->limit_index == LIMIT_LOW)
+
+ 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 (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
+ tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
+ uint64_t adjusted;
+
+ adjusted = throtl_adjusted_limit(tg->bps[rw][LIMIT_LOW], td);
+ ret = min(tg->bps[rw][LIMIT_MAX], adjusted);
+ }
return ret;
}
static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
{
struct blkcg_gq *blkg = tg_to_blkg(tg);
+ struct throtl_data *td;
unsigned int ret;
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
return UINT_MAX;
- ret = tg->iops[rw][tg->td->limit_index];
+ 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 (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
+ tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
+ uint64_t adjusted;
+
+ adjusted = throtl_adjusted_limit(tg->iops[rw][LIMIT_LOW], td);
+ if (adjusted > UINT_MAX)
+ adjusted = UINT_MAX;
+ ret = min_t(unsigned int, tg->iops[rw][LIMIT_MAX], adjusted);
+ }
return ret;
}
@@ -1677,6 +1720,7 @@ static void throtl_upgrade_state(struct throtl_data *td)
td->limit_index = LIMIT_MAX;
td->low_upgrade_time = jiffies;
+ td->scale = 0;
rcu_read_lock();
blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
struct throtl_grp *tg = blkg_to_tg(blkg);
@@ -1694,6 +1738,13 @@ static void throtl_upgrade_state(struct throtl_data *td)
static void throtl_downgrade_state(struct throtl_data *td, int new)
{
+ td->scale /= 2;
+
+ if (td->scale) {
+ td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
+ return;
+ }
+
td->limit_index = new;
td->low_downgrade_time = jiffies;
}