block: add sysfs file for controlling io stats accounting
This allows us to turn off disk stat accounting completely, for the cases
where the 0.5-1% reduction in system time is important.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index ae75c04..ca69f3d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -64,11 +64,12 @@
static void drive_stat_acct(struct request *rq, int new_io)
{
+ struct gendisk *disk = rq->rq_disk;
struct hd_struct *part;
int rw = rq_data_dir(rq);
int cpu;
- if (!blk_fs_request(rq) || !rq->rq_disk)
+ if (!blk_fs_request(rq) || !disk || !blk_queue_io_stat(disk->queue))
return;
cpu = part_stat_lock();
@@ -599,8 +600,7 @@
q->request_fn = rfn;
q->prep_rq_fn = NULL;
q->unplug_fn = generic_unplug_device;
- q->queue_flags = (1 << QUEUE_FLAG_CLUSTER |
- 1 << QUEUE_FLAG_STACKABLE);
+ q->queue_flags = QUEUE_FLAG_DEFAULT;
q->queue_lock = lock;
blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK);
@@ -1663,6 +1663,55 @@
}
EXPORT_SYMBOL(blkdev_dequeue_request);
+static void blk_account_io_completion(struct request *req, unsigned int bytes)
+{
+ struct gendisk *disk = req->rq_disk;
+
+ if (!disk || !blk_queue_io_stat(disk->queue))
+ return;
+
+ if (blk_fs_request(req)) {
+ const int rw = rq_data_dir(req);
+ struct hd_struct *part;
+ int cpu;
+
+ cpu = part_stat_lock();
+ part = disk_map_sector_rcu(req->rq_disk, req->sector);
+ part_stat_add(cpu, part, sectors[rw], bytes >> 9);
+ part_stat_unlock();
+ }
+}
+
+static void blk_account_io_done(struct request *req)
+{
+ struct gendisk *disk = req->rq_disk;
+
+ if (!disk || !blk_queue_io_stat(disk->queue))
+ return;
+
+ /*
+ * Account IO completion. bar_rq isn't accounted as a normal
+ * IO on queueing nor completion. Accounting the containing
+ * request is enough.
+ */
+ if (blk_fs_request(req) && req != &req->q->bar_rq) {
+ unsigned long duration = jiffies - req->start_time;
+ const int rw = rq_data_dir(req);
+ struct hd_struct *part;
+ int cpu;
+
+ cpu = part_stat_lock();
+ part = disk_map_sector_rcu(disk, req->sector);
+
+ part_stat_inc(cpu, part, ios[rw]);
+ part_stat_add(cpu, part, ticks[rw], duration);
+ part_round_stats(cpu, part);
+ part_dec_in_flight(part);
+
+ part_stat_unlock();
+ }
+}
+
/**
* __end_that_request_first - end I/O on a request
* @req: the request being processed
@@ -1698,16 +1747,7 @@
(unsigned long long)req->sector);
}
- if (blk_fs_request(req) && req->rq_disk) {
- const int rw = rq_data_dir(req);
- struct hd_struct *part;
- int cpu;
-
- cpu = part_stat_lock();
- part = disk_map_sector_rcu(req->rq_disk, req->sector);
- part_stat_add(cpu, part, sectors[rw], nr_bytes >> 9);
- part_stat_unlock();
- }
+ blk_account_io_completion(req, nr_bytes);
total_bytes = bio_nbytes = 0;
while ((bio = req->bio) != NULL) {
@@ -1787,8 +1827,6 @@
*/
static void end_that_request_last(struct request *req, int error)
{
- struct gendisk *disk = req->rq_disk;
-
if (blk_rq_tagged(req))
blk_queue_end_tag(req->q, req);
@@ -1800,27 +1838,7 @@
blk_delete_timer(req);
- /*
- * Account IO completion. bar_rq isn't accounted as a normal
- * IO on queueing nor completion. Accounting the containing
- * request is enough.
- */
- if (disk && blk_fs_request(req) && req != &req->q->bar_rq) {
- unsigned long duration = jiffies - req->start_time;
- const int rw = rq_data_dir(req);
- struct hd_struct *part;
- int cpu;
-
- cpu = part_stat_lock();
- part = disk_map_sector_rcu(disk, req->sector);
-
- part_stat_inc(cpu, part, ios[rw]);
- part_stat_add(cpu, part, ticks[rw], duration);
- part_round_stats(cpu, part);
- part_dec_in_flight(part);
-
- part_stat_unlock();
- }
+ blk_account_io_done(req);
if (req->end_io)
req->end_io(req, error);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b538ab8..e29ddfc 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -197,6 +197,27 @@
return ret;
}
+static ssize_t queue_iostats_show(struct request_queue *q, char *page)
+{
+ return queue_var_show(blk_queue_io_stat(q), page);
+}
+
+static ssize_t queue_iostats_store(struct request_queue *q, const char *page,
+ size_t count)
+{
+ unsigned long stats;
+ ssize_t ret = queue_var_store(&stats, page, count);
+
+ spin_lock_irq(q->queue_lock);
+ if (stats)
+ queue_flag_set(QUEUE_FLAG_IO_STAT, q);
+ else
+ queue_flag_clear(QUEUE_FLAG_IO_STAT, q);
+ spin_unlock_irq(q->queue_lock);
+
+ return ret;
+}
+
static struct queue_sysfs_entry queue_requests_entry = {
.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
.show = queue_requests_show,
@@ -249,6 +270,12 @@
.store = queue_rq_affinity_store,
};
+static struct queue_sysfs_entry queue_iostats_entry = {
+ .attr = {.name = "iostats", .mode = S_IRUGO | S_IWUSR },
+ .show = queue_iostats_show,
+ .store = queue_iostats_store,
+};
+
static struct attribute *default_attrs[] = {
&queue_requests_entry.attr,
&queue_ra_entry.attr,
@@ -259,6 +286,7 @@
&queue_nonrot_entry.attr,
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,
+ &queue_iostats_entry.attr,
NULL,
};
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 75426e4..d08c4b8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -451,6 +451,11 @@
#define QUEUE_FLAG_STACKABLE 13 /* supports request stacking */
#define QUEUE_FLAG_NONROT 14 /* non-rotational device (SSD) */
#define QUEUE_FLAG_VIRT QUEUE_FLAG_NONROT /* paravirt device */
+#define QUEUE_FLAG_IO_STAT 15 /* do IO stats */
+
+#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
+ (1 << QUEUE_FLAG_CLUSTER) | \
+ 1 << QUEUE_FLAG_STACKABLE)
static inline int queue_is_locked(struct request_queue *q)
{
@@ -567,6 +572,7 @@
#define blk_queue_stopped(q) test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
#define blk_queue_nomerges(q) test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
#define blk_queue_nonrot(q) test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)
+#define blk_queue_io_stat(q) test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
#define blk_queue_flushing(q) ((q)->ordseq)
#define blk_queue_stackable(q) \
test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)