linux/block
Corrado Zoccolo cf7c25cf91 cfq-iosched: fix next_rq computation
Cfq has a bug in computation of next_rq, that affects transition
between multiple sequential request streams in a single queue
(e.g.: two sequential buffered writers of the same priority),
causing the alternation between the two streams for a transient period.

  8,0    1    18737     0.260400660  5312  D   W 141653311 + 256
  8,0    1    20839     0.273239461  5400  D   W 141653567 + 256
  8,0    1    20841     0.276343885  5394  D   W 142803919 + 256
  8,0    1    20843     0.279490878  5394  D   W 141668927 + 256
  8,0    1    20845     0.292459993  5400  D   W 142804175 + 256
  8,0    1    20847     0.295537247  5400  D   W 141668671 + 256
  8,0    1    20849     0.298656337  5400  D   W 142804431 + 256
  8,0    1    20851     0.311481148  5394  D   W 141668415 + 256
  8,0    1    20853     0.314421305  5394  D   W 142804687 + 256
  8,0    1    20855     0.318960112  5400  D   W 142804943 + 256

The fix makes sure that the next_rq is computed from the last
dispatched request, and not affected by merging.

  8,0    1    37776     4.305161306     0  D   W 141738087 + 256
  8,0    1    37778     4.308298091     0  D   W 141738343 + 256
  8,0    1    37780     4.312885190     0  D   W 141738599 + 256
  8,0    1    37782     4.315933291     0  D   W 141738855 + 256
  8,0    1    37784     4.319064459     0  D   W 141739111 + 256
  8,0    1    37786     4.331918431  5672  D   W 142803007 + 256
  8,0    1    37788     4.334930332  5672  D   W 142803263 + 256
  8,0    1    37790     4.337902723  5672  D   W 142803519 + 256
  8,0    1    37792     4.342359774  5672  D   W 142803775 + 256
  8,0    1    37794     4.345318286     0  D   W 142804031 + 256

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-08 17:16:46 +01:00
..
blk-barrier.c block: allow large discard requests 2009-10-01 21:19:34 +02:00
blk-core.c block: silently error unsupported empty barriers too 2009-10-24 14:14:31 +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: fix next_rq computation 2009-11-08 17:16:46 +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/scsi_ioctl.c: quiet sparse noise 2009-11-04 09:10:33 +01:00