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Message-ID: <20100409041428.23105.51779.stgit@austin.mtv.corp.google.com>
Date: Thu, 08 Apr 2010 21:15:10 -0700
From: Divyesh Shah <dpshah@...gle.com>
To: jens.axboe@...cle.com, vgoyal@...hat.com
Cc: linux-kernel@...r.kernel.org, nauman@...gle.com,
ctalbott@...gle.com
Subject: [PATCH 2/3] blkio: Add io_queued and avg_queue_size stats
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<dpshah@...gle.com>
---
Documentation/cgroups/blkio-controller.txt | 11 +++
block/blk-cgroup.c | 98 +++++++++++++++++++++++++++-
block/blk-cgroup.h | 20 +++++-
block/cfq-iosched.c | 11 +++
4 files changed, 134 insertions(+), 6 deletions(-)
diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 810e301..6e52e7c 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -139,6 +139,17 @@ Details of cgroup files
cgroup. This is further divided by the type of operation - read or
write, sync or async.
+- blkio.io_queued
+ - Total number of requests queued up at any given instant for this
+ cgroup. This is further divided by the type of operation - read or
+ write, sync or async.
+
+- blkio.avg_queue_size
+ - Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y.
+ The average queue size for this cgroup over the entire time of this
+ cgroup's existence. Queue size samples are taken each time one of the
+ queues of this cgroup gets a timeslice.
+
- blkio.dequeue
- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This
gives the statistics about how many a times a group was dequeued
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d23b538..1e0c497 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -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
@@ -425,14 +505,22 @@ struct cftype blkio_files[] = {
.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
};
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 470a29d..bea7f3b 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -36,10 +36,13 @@ enum stat_type {
BLKIO_STAT_WAIT_TIME,
/* Number of IOs merged */
BLKIO_STAT_MERGED,
+ /* Number of IOs queued up */
+ BLKIO_STAT_QUEUED,
/* All the single valued stats go below this */
BLKIO_STAT_TIME,
BLKIO_STAT_SECTORS,
#ifdef CONFIG_DEBUG_BLK_CGROUP
+ BLKIO_STAT_AVG_QUEUE_SIZE,
BLKIO_STAT_DEQUEUE
#endif
};
@@ -63,8 +66,12 @@ struct blkio_group_stats {
/* total disk time and nr sectors dispatched by this group */
uint64_t time;
uint64_t sectors;
- uint64_t stat_arr[BLKIO_STAT_MERGED + 1][BLKIO_STAT_TOTAL];
+ uint64_t stat_arr[BLKIO_STAT_QUEUED + 1][BLKIO_STAT_TOTAL];
#ifdef CONFIG_DEBUG_BLK_CGROUP
+ /* Sum of number of IOs queued across all samples */
+ uint64_t avg_queue_size_sum;
+ /* Count of samples taken for average */
+ uint64_t avg_queue_size_samples;
/* How many times this group has been removed from service tree */
unsigned long dequeue;
#endif
@@ -127,10 +134,13 @@ static inline char *blkg_path(struct blkio_group *blkg)
{
return blkg->path;
}
+void blkiocg_update_set_active_queue_stats(struct blkio_group *blkg);
void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
unsigned long dequeue);
#else
static inline char *blkg_path(struct blkio_group *blkg) { return NULL; }
+static inline void blkiocg_update_set_active_queue_stats(
+ struct blkio_group *blkg) {}
static inline void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
unsigned long dequeue) {}
#endif
@@ -152,6 +162,10 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
uint64_t start_time, uint64_t io_start_time, bool direction, bool sync);
void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
bool sync);
+void blkiocg_update_request_add_stats(struct blkio_group *blkg,
+ struct blkio_group *curr_blkg, bool direction, bool sync);
+void blkiocg_update_request_remove_stats(struct blkio_group *blkg,
+ bool direction, bool sync);
#else
struct cgroup;
static inline struct blkio_cgroup *
@@ -175,5 +189,9 @@ static inline void blkiocg_update_completion_stats(struct blkio_group *blkg,
bool sync) {}
static inline void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
bool direction, bool sync) {}
+static inline void blkiocg_update_request_add_stats(struct blkio_group *blkg,
+ struct blkio_group *curr_blkg, bool direction, bool sync) {}
+static inline void blkiocg_update_request_remove_stats(struct blkio_group *blkg,
+ bool direction, bool sync) {}
#endif
#endif /* _BLK_CGROUP_H */
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4eb1906..8e0b86a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1380,7 +1380,12 @@ static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
{
elv_rb_del(&cfqq->sort_list, rq);
cfqq->queued[rq_is_sync(rq)]--;
+ blkiocg_update_request_remove_stats(&cfqq->cfqg->blkg, rq_data_dir(rq),
+ rq_is_sync(rq));
cfq_add_rq_rb(rq);
+ blkiocg_update_request_add_stats(
+ &cfqq->cfqg->blkg, &cfqq->cfqd->serving_group->blkg,
+ rq_data_dir(rq), rq_is_sync(rq));
}
static struct request *
@@ -1436,6 +1441,8 @@ static void cfq_remove_request(struct request *rq)
cfq_del_rq_rb(rq);
cfqq->cfqd->rq_queued--;
+ blkiocg_update_request_remove_stats(&cfqq->cfqg->blkg, rq_data_dir(rq),
+ rq_is_sync(rq));
if (rq_is_meta(rq)) {
WARN_ON(!cfqq->meta_pending);
cfqq->meta_pending--;
@@ -1527,6 +1534,7 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
if (cfqq) {
cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
cfqd->serving_prio, cfqd->serving_type);
+ blkiocg_update_set_active_queue_stats(&cfqq->cfqg->blkg);
cfqq->slice_start = 0;
cfqq->dispatch_start = jiffies;
cfqq->allocated_slice = 0;
@@ -3213,6 +3221,9 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
list_add_tail(&rq->queuelist, &cfqq->fifo);
cfq_add_rq_rb(rq);
+ blkiocg_update_request_add_stats(&cfqq->cfqg->blkg,
+ &cfqd->serving_group->blkg, rq_data_dir(rq),
+ rq_is_sync(rq));
cfq_rq_enqueued(cfqd, cfqq, rq);
}
--
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