Track I/O statistics per I/O priority and export these statistics to
debugfs. These statistics help developers of the deadline scheduler.
Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Cc: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/mq-deadline.c | 100 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 100 insertions(+)
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index aba672a5be1e..04d9d6b3745b 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -51,6 +51,19 @@ enum dd_prio {
enum { DD_PRIO_COUNT = 3 };
+/* I/O statistics per I/O priority. */
+struct io_stats_per_prio {
+ local_t inserted;
+ local_t merged;
+ local_t dispatched;
+ local_t completed;
+};
+
+/* I/O statistics for all I/O priorities (enum dd_prio). */
+struct io_stats {
+ struct io_stats_per_prio stats[DD_PRIO_COUNT];
+};
+
/*
* Deadline scheduler data per I/O priority (enum dd_prio). Requests are
* present on both sort_list[] and fifo_list[].
@@ -75,6 +88,8 @@ struct deadline_data {
unsigned int batching; /* number of sequential requests made */
unsigned int starved; /* times reads have starved writes */
+ struct io_stats __percpu *stats;
+
/*
* settings that change how the i/o scheduler behaves
*/
@@ -88,6 +103,33 @@ struct deadline_data {
spinlock_t zone_lock;
};
+/* Count one event of type 'event_type' and with I/O priority 'prio' */
+#define dd_count(dd, event_type, prio) do { \
+ struct io_stats *io_stats = get_cpu_ptr((dd)->stats); \
+ \
+ BUILD_BUG_ON(!__same_type((dd), struct deadline_data *)); \
+ BUILD_BUG_ON(!__same_type((prio), enum dd_prio)); \
+ local_inc(&io_stats->stats[(prio)].event_type); \
+ put_cpu_ptr(io_stats); \
+} while (0)
+
+/*
+ * Returns the total number of dd_count(dd, event_type, prio) calls across all
+ * CPUs. No locking or barriers since it is fine if the returned sum is slightly
+ * outdated.
+ */
+#define dd_sum(dd, event_type, prio) ({ \
+ unsigned int cpu; \
+ u32 sum = 0; \
+ \
+ BUILD_BUG_ON(!__same_type((dd), struct deadline_data *)); \
+ BUILD_BUG_ON(!__same_type((prio), enum dd_prio)); \
+ for_each_present_cpu(cpu) \
+ sum += local_read(&per_cpu_ptr((dd)->stats, cpu)-> \
+ stats[(prio)].event_type); \
+ sum; \
+})
+
/* Maps an I/O priority class to a deadline scheduler priority. */
static const enum dd_prio ioprio_class_to_prio[] = {
[IOPRIO_CLASS_NONE] = DD_BE_PRIO,
@@ -187,9 +229,12 @@ static void dd_request_merged(struct request_queue *q, struct request *req,
static void dd_merged_requests(struct request_queue *q, struct request *req,
struct request *next)
{
+ struct deadline_data *dd = q->elevator->elevator_data;
const u8 ioprio_class = dd_rq_ioclass(next);
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
+ dd_count(dd, merged, prio);
+
/*
* if next expires before rq, assign its expire time to rq
* and move into next position (next will be deleted) in fifo
@@ -225,6 +270,12 @@ deadline_move_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
deadline_remove_request(rq->q, per_prio, rq);
}
+/* Number of requests queued for a given priority level. */
+static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
+{
+ return dd_sum(dd, inserted, prio) - dd_sum(dd, completed, prio);
+}
+
/*
* deadline_check_fifo returns 0 if there are no expired requests on the fifo,
* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
@@ -319,6 +370,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd,
{
struct request *rq, *next_rq;
enum dd_data_dir data_dir;
+ enum dd_prio prio;
+ u8 ioprio_class;
lockdep_assert_held(&dd->lock);
@@ -408,6 +461,9 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd,
dd->batching++;
deadline_move_request(dd, per_prio, rq);
done:
+ ioprio_class = dd_rq_ioclass(rq);
+ prio = ioprio_class_to_prio[ioprio_class];
+ dd_count(dd, dispatched, prio);
/*
* If the request needs its target zone locked, do it.
*/
@@ -491,6 +547,8 @@ static void dd_exit_sched(struct elevator_queue *e)
WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE]));
}
+ free_percpu(dd->stats);
+
kfree(dd);
}
@@ -514,6 +572,11 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
eq->elevator_data = dd;
+ dd->stats = alloc_percpu_gfp(typeof(*dd->stats),
+ GFP_KERNEL | __GFP_ZERO);
+ if (!dd->stats)
+ goto free_dd;
+
for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
struct dd_per_prio *per_prio = &dd->per_prio[prio];
@@ -535,6 +598,9 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
q->elevator = eq;
return 0;
+free_dd:
+ kfree(dd);
+
put_eq:
kobject_put(&eq->kobj);
return ret;
@@ -614,6 +680,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
blk_req_zone_write_unlock(rq);
prio = ioprio_class_to_prio[ioprio_class];
+ dd_count(dd, inserted, prio);
if (blk_mq_sched_try_insert_merge(q, rq))
return;
@@ -692,6 +759,8 @@ static void dd_finish_request(struct request *rq)
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
struct dd_per_prio *per_prio = &dd->per_prio[prio];
+ dd_count(dd, completed, prio);
+
if (blk_queue_is_zoned(q)) {
unsigned long flags;
@@ -873,6 +942,35 @@ static int dd_async_depth_show(void *data, struct seq_file *m)
return 0;
}
+static int dd_queued_show(void *data, struct seq_file *m)
+{
+ struct request_queue *q = data;
+ struct deadline_data *dd = q->elevator->elevator_data;
+
+ seq_printf(m, "%u %u %u\n", dd_queued(dd, DD_RT_PRIO),
+ dd_queued(dd, DD_BE_PRIO),
+ dd_queued(dd, DD_IDLE_PRIO));
+ return 0;
+}
+
+/* Number of requests owned by the block driver for a given priority. */
+static u32 dd_owned_by_driver(struct deadline_data *dd, enum dd_prio prio)
+{
+ return dd_sum(dd, dispatched, prio) + dd_sum(dd, merged, prio)
+ - dd_sum(dd, completed, prio);
+}
+
+static int dd_owned_by_driver_show(void *data, struct seq_file *m)
+{
+ struct request_queue *q = data;
+ struct deadline_data *dd = q->elevator->elevator_data;
+
+ seq_printf(m, "%u %u %u\n", dd_owned_by_driver(dd, DD_RT_PRIO),
+ dd_owned_by_driver(dd, DD_BE_PRIO),
+ dd_owned_by_driver(dd, DD_IDLE_PRIO));
+ return 0;
+}
+
#define DEADLINE_DISPATCH_ATTR(prio) \
static void *deadline_dispatch##prio##_start(struct seq_file *m, \
loff_t *pos) \
@@ -941,6 +1039,8 @@ static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
{"dispatch0", 0400, .seq_ops = &deadline_dispatch0_seq_ops},
{"dispatch1", 0400, .seq_ops = &deadline_dispatch1_seq_ops},
{"dispatch2", 0400, .seq_ops = &deadline_dispatch2_seq_ops},
+ {"owned_by_driver", 0400, dd_owned_by_driver_show},
+ {"queued", 0400, dd_queued_show},
{},
};
#undef DEADLINE_QUEUE_DDIR_ATTRS
