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blkio: Add io_queued and avg_queue_size stats

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These stats are useful for getting a feel for the queue depth of the cgroup,
i.e., how filled up its queues are at a given instant and over the existence of
the cgroup. This ability is useful when debugging problems in the wild as it
helps understand the application's IO pattern w/o having to read through the
userspace code (coz its tedious or just not available) or w/o the ability
to run blktrace (since you may not have root access and/or not want to disturb
performance).

Signed-off-by: Divyesh Shah<[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Divyesh Shah 2010-04-08 21:15:10 -07:00 • committed by Jens Axboe
commit cdc1184cf4
4 changed files with 134 additions and 6 deletions
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98
block/blk-cgroup.c
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@ -81,6 +81,71 @@ static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
stat[BLKIO_STAT_ASYNC] += add;
}
/*
* Decrements the appropriate stat variable if non-zero depending on the
* request type. Panics on value being zero.
* This should be called with the blkg->stats_lock held.
*/
static void blkio_check_and_dec_stat(uint64_t *stat, bool direction, bool sync)
{
if (direction) {
BUG_ON(stat[BLKIO_STAT_WRITE] == 0);
stat[BLKIO_STAT_WRITE]--;
} else {
BUG_ON(stat[BLKIO_STAT_READ] == 0);
stat[BLKIO_STAT_READ]--;
}
if (sync) {
BUG_ON(stat[BLKIO_STAT_SYNC] == 0);
stat[BLKIO_STAT_SYNC]--;
} else {
BUG_ON(stat[BLKIO_STAT_ASYNC] == 0);
stat[BLKIO_STAT_ASYNC]--;
}
}
#ifdef CONFIG_DEBUG_BLK_CGROUP
void blkiocg_update_set_active_queue_stats(struct blkio_group *blkg)
{
unsigned long flags;
struct blkio_group_stats *stats;
spin_lock_irqsave(&blkg->stats_lock, flags);
stats = &blkg->stats;
stats->avg_queue_size_sum +=
stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_READ] +
stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE];
stats->avg_queue_size_samples++;
spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_set_active_queue_stats);
#endif
void blkiocg_update_request_add_stats(struct blkio_group *blkg,
struct blkio_group *curr_blkg, bool direction,
bool sync)
{
unsigned long flags;
spin_lock_irqsave(&blkg->stats_lock, flags);
blkio_add_stat(blkg->stats.stat_arr[BLKIO_STAT_QUEUED], 1, direction,
sync);
spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_request_add_stats);
void blkiocg_update_request_remove_stats(struct blkio_group *blkg,
bool direction, bool sync)
{
unsigned long flags;
spin_lock_irqsave(&blkg->stats_lock, flags);
blkio_check_and_dec_stat(blkg->stats.stat_arr[BLKIO_STAT_QUEUED],
direction, sync);
spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_request_remove_stats);
void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time)
{
unsigned long flags;
@ -253,14 +318,18 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
struct blkio_cgroup *blkcg;
struct blkio_group *blkg;
struct hlist_node *n;
struct blkio_group_stats *stats;
uint64_t queued[BLKIO_STAT_TOTAL];
int i;
blkcg = cgroup_to_blkio_cgroup(cgroup);
spin_lock_irq(&blkcg->lock);
hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
spin_lock(&blkg->stats_lock);
stats = &blkg->stats;
memset(stats, 0, sizeof(struct blkio_group_stats));
for (i = 0; i < BLKIO_STAT_TOTAL; i++)
queued[i] = blkg->stats.stat_arr[BLKIO_STAT_QUEUED][i];
memset(&blkg->stats, 0, sizeof(struct blkio_group_stats));
for (i = 0; i < BLKIO_STAT_TOTAL; i++)
blkg->stats.stat_arr[BLKIO_STAT_QUEUED][i] = queued[i];
spin_unlock(&blkg->stats_lock);
}
spin_unlock_irq(&blkcg->lock);
@ -323,6 +392,15 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg,
return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
blkg->stats.sectors, cb, dev);
#ifdef CONFIG_DEBUG_BLK_CGROUP
if (type == BLKIO_STAT_AVG_QUEUE_SIZE) {
uint64_t sum = blkg->stats.avg_queue_size_sum;
uint64_t samples = blkg->stats.avg_queue_size_samples;
if (samples)
do_div(sum, samples);
else
sum = 0;
return blkio_fill_stat(key_str, MAX_KEY_LEN - 1, sum, cb, dev);
}
if (type == BLKIO_STAT_DEQUEUE)
return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
blkg->stats.dequeue, cb, dev);
@ -376,8 +454,10 @@ SHOW_FUNCTION_PER_GROUP(io_serviced, BLKIO_STAT_SERVICED, 1);
SHOW_FUNCTION_PER_GROUP(io_service_time, BLKIO_STAT_SERVICE_TIME, 1);
SHOW_FUNCTION_PER_GROUP(io_wait_time, BLKIO_STAT_WAIT_TIME, 1);
SHOW_FUNCTION_PER_GROUP(io_merged, BLKIO_STAT_MERGED, 1);
SHOW_FUNCTION_PER_GROUP(io_queued, BLKIO_STAT_QUEUED, 1);
#ifdef CONFIG_DEBUG_BLK_CGROUP
SHOW_FUNCTION_PER_GROUP(dequeue, BLKIO_STAT_DEQUEUE, 0);
SHOW_FUNCTION_PER_GROUP(avg_queue_size, BLKIO_STAT_AVG_QUEUE_SIZE, 0);
#endif
#undef SHOW_FUNCTION_PER_GROUP
@ -424,15 +504,23 @@ struct cftype blkio_files[] = {
.name = "io_merged",
.read_map = blkiocg_io_merged_read,
},
{
.name = "io_queued",
.read_map = blkiocg_io_queued_read,
},
{
.name = "reset_stats",
.write_u64 = blkiocg_reset_stats,
},
#ifdef CONFIG_DEBUG_BLK_CGROUP
{
{
.name = "avg_queue_size",
.read_map = blkiocg_avg_queue_size_read,
},
{
.name = "dequeue",
.read_map = blkiocg_dequeue_read,
},
},
#endif
};