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-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,
};