Paolo Valente bcd5642607 block, bfq: preserve a low latency also with NCQ-capable drives ... I/O schedulers typically allow NCQ-capable drives to prefetch I/O requests, as NCQ boosts the throughput exactly by prefetching and internally reordering requests. Unfortunately, as discussed in detail and shown experimentally in [1], this may cause fairness and latency guarantees to be violated. The main problem is that the internal scheduler of an NCQ-capable drive may postpone the service of some unlucky (prefetched) requests as long as it deems serving other requests more appropriate to boost the throughput. This patch addresses this issue by not disabling device idling for weight-raised queues, even if the device supports NCQ. This allows BFQ to start serving a new queue, and therefore allows the drive to prefetch new requests, only after the idling timeout expires. At that time, all the outstanding requests of the expired queue have been most certainly served. [1] P. Valente and M. Andreolini, "Improving Application Responsiveness with the BFQ Disk I/O Scheduler", Proceedings of the 5th Annual International Systems and Storage Conference (SYSTOR '12), June 2012. Slightly extended version: http://algogroup.unimore.it/people/paolo/disk_sched/bfq-v1-suite- results.pdf 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>		2017-04-19 08:30:26 -06:00
..
partitions	partitions/efi: Fix integer overflow in GPT size calculation	2017-01-17 09:02:31 -07:00
badblocks.c	badblocks: badblocks_set/clear update unacked_exist	2016-10-21 15:45:47 -06:00
bfq-iosched.c	block, bfq: preserve a low latency also with NCQ-capable drives	2017-04-19 08:30:26 -06:00
bio-integrity.c	block: remove bio_is_rw	2016-10-28 08:45:17 -06:00
bio.c	block: trace completion of all bios.	2017-04-07 09:40:52 -06:00
blk-cgroup.c	blkcg: allocate struct blkcg_gq outside request queue spinlock	2017-03-29 11:27:19 -06:00
blk-core.c	block: trace completion of all bios.	2017-04-07 09:40:52 -06:00
blk-exec.c	block: introduce blk_rq_is_passthrough	2017-01-31 14:00:34 -07:00
blk-flush.c	block: remove outdated part of blkdev_issue_flush() comment	2017-03-24 15:41:30 -06:00
blk-integrity.c	block: constify struct blk_integrity_profile	2017-03-24 20:34:39 -06:00
blk-ioc.c	Merge branch 'for-linus' of git://git.kernel.dk/linux-block	2017-03-03 10:53:35 -08:00
blk-lib.c	block: remove the discard_zeroes_data flag	2017-04-08 11:25:38 -06:00
blk-map.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h>	2017-03-02 08:42:36 +01:00
blk-merge.c	block: implement splitting of REQ_OP_WRITE_ZEROES bios	2017-04-08 11:25:38 -06:00
blk-mq-cpumap.c	blk-mq: export blk_mq_map_queues	2016-11-08 17:30:00 -05:00
blk-mq-debugfs.c	blk-mq: Show symbolic names for hctx state and flags	2017-04-10 16:13:33 -06:00
blk-mq-pci.c	blk-mq-pci: Fix two spelling mistakes	2017-03-29 11:09:51 -06:00
blk-mq-sched.c	blk-mq-sched: provide hooks for initializing hardware queue data	2017-04-07 12:45:41 -06:00
blk-mq-sched.h	blk-mq-sched: make completed_request() callback more useful	2017-04-14 14:06:57 -06:00
blk-mq-sysfs.c	blk-mq: free hctx->cpumask in release handler of hctx's kobject	2017-03-08 09:56:12 -07:00
blk-mq-tag.c	blk-mq: add shallow depth option for blk_mq_get_tag()	2017-04-14 14:06:54 -06:00
blk-mq-tag.h	blk-mq-sched: Allocate sched reserved tags as specified in the original queue tagset	2017-03-02 08:56:04 -07:00
blk-mq-virtio.c	blk-mq: provide a default queue mapping for virtio device	2017-02-27 20:54:05 +02:00
blk-mq.c	blk-mq-sched: make completed_request() callback more useful	2017-04-14 14:06:57 -06:00
blk-mq.h	blk-mq: add shallow depth option for blk_mq_get_tag()	2017-04-14 14:06:54 -06:00
blk-settings.c	block: remove the discard_zeroes_data flag	2017-04-08 11:25:38 -06:00
blk-softirq.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/topology.h>	2017-03-02 08:42:26 +01:00
blk-stat.c	blk-throttle: add a mechanism to estimate IO latency	2017-03-28 08:02:20 -06:00
blk-stat.h	blk-throttle: add a mechanism to estimate IO latency	2017-03-28 08:02:20 -06:00
blk-sysfs.c	block: remove the discard_zeroes_data flag	2017-04-08 11:25:38 -06:00
blk-tag.c	blk-mq-sched: add framework for MQ capable IO schedulers	2017-01-17 10:04:20 -07:00
blk-throttle.c	blk-throttle: add latency target support	2017-03-28 08:02:20 -06:00
blk-timeout.c	block: remove REQ_NO_TIMEOUT flag	2015-12-22 09:38:34 -07:00
blk-wbt.c	block: Fix list corruption of blk stats callback list	2017-04-11 08:09:14 -06:00
blk-wbt.h	block: track request size in blk_issue_stat	2017-03-28 08:02:20 -06:00
blk-zoned.c	block: Rename blk_queue_zone_size and bdev_zone_size	2017-01-12 07:58:32 -07:00
blk.h	blk-throttle: add a mechanism to estimate IO latency	2017-03-28 08:02:20 -06:00
bounce.c	Merge branch 'for-linus' of git://git.kernel.dk/linux-block	2015-09-19 18:57:09 -07:00
bsg-lib.c	block: split scsi_request out of struct request	2017-01-27 15:08:35 -07:00
bsg.c	lib/vsprintf.c: remove %Z support	2017-02-27 18:43:47 -08:00
cfq-iosched.c	cfq: Disable writeback throttling by default	2017-04-05 08:15:08 -06:00
cmdline-parser.c	block: remove unrelated header files and export symbol	2014-01-21 20:18:26 -08:00
compat_ioctl.c	block: remove the discard_zeroes_data flag	2017-04-08 11:25:38 -06:00
deadline-iosched.c	block: enumify ELEVATOR_*_MERGE	2017-02-08 13:43:06 -07:00
elevator.c	blk-mq-sched: fix crash in switch error path	2017-04-07 08:56:48 -06:00
genhd.c	block: Fix oops scsi_disk_get()	2017-03-22 20:11:37 -06:00
ioctl.c	block: remove the discard_zeroes_data flag	2017-04-08 11:25:38 -06:00
ioprio.c	sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h>	2017-03-02 08:42:38 +01:00
Kconfig	blk-throttle: add configure option for new .low interface	2017-03-28 08:02:20 -06:00
Kconfig.iosched	block, bfq: add full hierarchical scheduling and cgroups support	2017-04-19 08:30:26 -06:00
kyber-iosched.c	blk-mq: introduce Kyber multiqueue I/O scheduler	2017-04-14 14:06:58 -06:00
Makefile	block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler	2017-04-19 08:29:02 -06:00
mq-deadline.c	block: enumify ELEVATOR_*_MERGE	2017-02-08 13:43:06 -07:00
noop-iosched.c	block: move existing elevator ops to union	2017-01-17 10:03:33 -07:00
opal_proto.h	block/sed-opal: allocate struct opal_dev dynamically	2017-02-17 12:41:47 -07:00
partition-generic.c	block: Rename blk_queue_zone_size and bdev_zone_size	2017-01-12 07:58:32 -07:00
scsi_ioctl.c	block, scsi: move the retries field to struct scsi_request	2017-04-05 12:05:08 -06:00
sed-opal.c	block: sed-opal: Tone down all the pr_* to debugs	2017-04-07 14:24:16 -06:00
t10-pi.c	block: constify struct blk_integrity_profile	2017-03-24 20:34:39 -06:00