block: add queue flag for SSD/non-rotational devices
We don't want to idle in AS/CFQ if the device doesn't have a seek
penalty. So add a QUEUE_FLAG_NONROT to indicate a non-rotational
device, low level drivers should set this flag upon discovery of
an SSD or similar device type.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/as-iosched.c b/block/as-iosched.c
index 80af925..4c6fafb 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -745,6 +745,12 @@
*/
static int as_can_anticipate(struct as_data *ad, struct request *rq)
{
+ /*
+ * SSD device without seek penalty, disable idling
+ */
+ if (blk_queue_nonrot(ad->q))
+ return 0;
+
if (!ad->io_context)
/*
* Last request submitted was a write
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 494b6fd..03a5953b 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -878,6 +878,12 @@
struct cfq_io_context *cic;
unsigned long sl;
+ /*
+ * SSD device without seek penalty, disable idling
+ */
+ if (blk_queue_nonrot(cfqd->queue))
+ return;
+
WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
WARN_ON(cfq_cfqq_slice_new(cfqq));
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 86f77ef..0cf3e61 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -442,6 +442,7 @@
#define QUEUE_FLAG_SAME_COMP 11 /* force complete on same CPU */
#define QUEUE_FLAG_FAIL_IO 12 /* fake timeout */
#define QUEUE_FLAG_STACKABLE 13 /* supports request stacking */
+#define QUEUE_FLAG_NONROT 14 /* non-rotational device (SSD) */
static inline int queue_is_locked(struct request_queue *q)
{
@@ -547,6 +548,7 @@
#define blk_queue_tagged(q) test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
#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_flushing(q) ((q)->ordseq)
#define blk_queue_stackable(q) \
test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)