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>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 75426e4b8cdf..d08c4b8219a6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -451,6 +451,11 @@ struct request_queue
 #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 @@ enum {
 #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)