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authorPaolo Valente <paolo.valente@linaro.org>2017-04-12 19:23:19 +0300
committerJens Axboe <axboe@fb.com>2017-04-19 17:30:26 +0300
commite01eff01d5c81f4dbba186299b16b08aa7316d5b (patch)
tree9a6cd957d0ca463247d3e57438cfec5e2702a661 /block/bfq-iosched.c
parentbf2b79e7c4b312aa6e1c661fb27e0dc4dd42f2c2 (diff)
downloadlinux-e01eff01d5c81f4dbba186299b16b08aa7316d5b.tar.xz
block, bfq: boost the throughput with random I/O on NCQ-capable HDDs
This patch is basically the counterpart, for NCQ-capable rotational devices, of the previous patch. Exactly as the previous patch does on flash-based devices and for any workload, this patch disables device idling on rotational devices, but only for random I/O. In fact, only with these queues disabling idling boosts the throughput on NCQ-capable rotational devices. To not break service guarantees, idling is disabled for NCQ-enabled rotational devices only when the same symmetry conditions considered in the previous patches hold. Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/bfq-iosched.c')
-rw-r--r--block/bfq-iosched.c16
1 files changed, 6 insertions, 10 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 208178478dc4..549f030509ef 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -6439,20 +6439,15 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq)
* The next variable takes into account the cases where idling
* boosts the throughput.
*
- * The value of the variable is computed considering that
- * idling is usually beneficial for the throughput if:
+ * The value of the variable is computed considering, first, that
+ * idling is virtually always beneficial for the throughput if:
* (a) the device is not NCQ-capable, or
* (b) regardless of the presence of NCQ, the device is rotational
- * and the request pattern for bfqq is I/O-bound (possible
- * throughput losses caused by granting idling to seeky queues
- * are mitigated by the fact that, in all scenarios where
- * boosting throughput is the best thing to do, i.e., in all
- * symmetric scenarios, only a minimal idle time is allowed to
- * seeky queues).
+ * and the request pattern for bfqq is I/O-bound and sequential.
*
* Secondly, and in contrast to the above item (b), idling an
* NCQ-capable flash-based device would not boost the
- * throughput even with intense I/O; rather it would lower
+ * throughput even with sequential I/O; rather it would lower
* the throughput in proportion to how fast the device
* is. Accordingly, the next variable is true if any of the
* above conditions (a) and (b) is true, and, in particular,
@@ -6460,7 +6455,8 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq)
* device.
*/
idling_boosts_thr = !bfqd->hw_tag ||
- (!blk_queue_nonrot(bfqd->queue) && bfq_bfqq_IO_bound(bfqq));
+ (!blk_queue_nonrot(bfqd->queue) && bfq_bfqq_IO_bound(bfqq) &&
+ bfq_bfqq_idle_window(bfqq));
/*
* The value of the next variable,