Commit 0b39920b authored by Tejun Heo's avatar Tejun Heo

cfq-iosched: collect stats from dead cfqgs

To support hierarchical stats, it's necessary to remember stats from
dead children.  Add cfqg->dead_stats and make a dying cfqg transfer
its stats to the parent's dead-stats.

The transfer happens form ->pd_offline_fn() and it is possible that
there are some residual IOs completing afterwards.  Currently, we lose
these stats.  Given that cgroup removal isn't a very high frequency
operation and the amount of residual IOs on offline are likely to be
nil or small, this shouldn't be a big deal and the complexity needed
to handle residual IOs - another callback and rather elaborate
synchronization to reach and lock the matching q - doesn't seem
Signed-off-by: default avatarTejun Heo <>
Acked-by: default avatarVivek Goyal <>
parent 689665af
......@@ -289,7 +289,8 @@ struct cfq_group {
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
struct cfq_ttime ttime;
struct cfqg_stats stats;
struct cfqg_stats stats; /* stats for this cfqg */
struct cfqg_stats dead_stats; /* stats pushed from dead children */
struct cfq_io_cq {
......@@ -709,6 +710,47 @@ static void cfqg_stats_reset(struct cfqg_stats *stats)
/* @to += @from */
static void cfqg_stats_merge(struct cfqg_stats *to, struct cfqg_stats *from)
/* queued stats shouldn't be cleared */
blkg_rwstat_merge(&to->service_bytes, &from->service_bytes);
blkg_rwstat_merge(&to->serviced, &from->serviced);
blkg_rwstat_merge(&to->merged, &from->merged);
blkg_rwstat_merge(&to->service_time, &from->service_time);
blkg_rwstat_merge(&to->wait_time, &from->wait_time);
blkg_stat_merge(&from->time, &from->time);
blkg_stat_merge(&to->unaccounted_time, &from->unaccounted_time);
blkg_stat_merge(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
blkg_stat_merge(&to->avg_queue_size_samples, &from->avg_queue_size_samples);
blkg_stat_merge(&to->dequeue, &from->dequeue);
blkg_stat_merge(&to->group_wait_time, &from->group_wait_time);
blkg_stat_merge(&to->idle_time, &from->idle_time);
blkg_stat_merge(&to->empty_time, &from->empty_time);
* Transfer @cfqg's stats to its parent's dead_stats so that the ancestors'
* recursive stats can still account for the amount used by this cfqg after
* it's gone.
static void cfqg_stats_xfer_dead(struct cfq_group *cfqg)
struct cfq_group *parent = cfqg_parent(cfqg);
if (unlikely(!parent))
cfqg_stats_merge(&parent->dead_stats, &cfqg->stats);
cfqg_stats_merge(&parent->dead_stats, &cfqg->dead_stats);
static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg) { return NULL; }
......@@ -1475,11 +1517,23 @@ static void cfq_pd_init(struct blkcg_gq *blkg)
cfqg->leaf_weight = blkg->blkcg->cfq_leaf_weight;
static void cfq_pd_offline(struct blkcg_gq *blkg)
* @blkg is going offline and will be ignored by
* blkg_[rw]stat_recursive_sum(). Transfer stats to the parent so
* that they don't get lost. If IOs complete after this point, the
* stats for them will be lost. Oh well...
static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
struct cfq_group *cfqg = blkg_to_cfqg(blkg);
......@@ -4408,6 +4462,7 @@ static struct blkcg_policy blkcg_policy_cfq = {
.cftypes = cfq_blkcg_files,
.pd_init_fn = cfq_pd_init,
.pd_offline_fn = cfq_pd_offline,
.pd_reset_stats_fn = cfq_pd_reset_stats,
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