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/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)