linux/block
Corrado Zoccolo 718eee0579 cfq-iosched: fairness for sync no-idle queues
Currently no-idle queues in cfq are not serviced fairly:
even if they can only dispatch a small number of requests at a time,
they have to compete with idling queues to be serviced, experiencing
large latencies.

We should notice, instead, that no-idle queues are the ones that would
benefit most from having low latency, in fact they are any of:
* processes with large think times (e.g. interactive ones like file
  managers)
* seeky (e.g. programs faulting in their code at startup)
* or marked as no-idle from upper levels, to improve latencies of those
  requests.

This patch improves the fairness and latency for those queues, by:
* separating sync idle, sync no-idle and async queues in separate
  service_trees, for each priority
* service all no-idle queues together
* and idling when the last no-idle queue has been serviced, to
  anticipate for more no-idle work
* the timeslices allotted for idle and no-idle service_trees are
  computed proportionally to the number of processes in each set.

Servicing all no-idle queues together should have a performance boost
for NCQ-capable drives, without compromising fairness.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-28 09:23:26 +01:00
..
blk-barrier.c block: allow large discard requests 2009-10-01 21:19:34 +02:00
blk-core.c block: Seperate read and write statistics of in_flight requests v2 2009-10-06 20:16:55 +02:00
blk-exec.c block: don't set REQ_NOMERGE unnecessarily 2009-04-28 07:37:33 +02:00
blk-integrity.c block: fix improper kobject release in blk_integrity_unregister 2009-07-28 09:11:14 +02:00
blk-ioc.c block: prevent possible io_context->refcount overflow 2009-06-10 23:07:15 +02:00
blk-iopoll.c block: use interrupts disabled version of raise_softirq_irqoff() 2009-09-11 14:33:32 +02:00
blk-map.c block: Use accessor functions for queue limits 2009-05-22 23:22:54 +02:00
blk-merge.c block: Seperate read and write statistics of in_flight requests v2 2009-10-06 20:16:55 +02:00
blk-settings.c blk-settings: fix function parameter kernel-doc notation 2009-10-12 08:20:47 +02:00
blk-softirq.c generic-ipi: remove CSD_FLAG_WAIT 2009-02-25 14:13:44 +01:00
blk-sysfs.c Add missing blk_trace_remove_sysfs to be in pair with blk_trace_init_sysfs 2009-10-01 21:15:46 +02:00
blk-tag.c block: use proper BLK_RW_ASYNC in blk_queue_start_tag() 2009-10-06 20:19:02 +02:00
blk-timeout.c block: clean up misc stuff after block layer timeout conversion 2009-04-28 07:37:34 +02:00
blk.h block: implement mixed merge of different failfast requests 2009-09-11 14:33:30 +02:00
bsg.c Driver-Core: extend devnode callbacks to provide permissions 2009-09-19 12:50:38 -07:00
cfq-iosched.c cfq-iosched: fairness for sync no-idle queues 2009-10-28 09:23:26 +01:00
compat_ioctl.c block: Topology ioctls 2009-10-03 20:52:01 +02:00
deadline-iosched.c block: convert to pos and nr_sectors accessors 2009-05-11 09:50:54 +02:00
elevator.c Merge branch 'for-linus' into for-2.6.33 2009-10-13 12:29:45 +02:00
genhd.c block: Seperate read and write statistics of in_flight requests v2 2009-10-06 20:16:55 +02:00
ioctl.c block: Topology ioctls 2009-10-03 20:52:01 +02:00
Kconfig Make SCSI SG v4 driver enabled by default and remove EXPERIMENTAL dependency, since udev depends on BSG 2009-08-04 22:10:17 +02:00
Kconfig.iosched block: CFQ is more than a desktop scheduler 2009-10-03 09:40:47 +02:00
Makefile block: remove the anticipatory IO scheduler 2009-10-03 09:37:51 +02:00
noop-iosched.c block: get rid of elevator_t typedef 2008-12-29 08:29:50 +01:00
scsi_ioctl.c block: call blk_scsi_ioctl_init() 2009-07-10 20:31:53 +02:00