tmp_suning_uos_patched/block
Vivek Goyal 7667aa0630 cfq-iosched: Take care of corner cases of group losing share due to deletion
If there is a sequential reader running in a group, we wait for next request
to come in that group after slice expiry and once new request is in, we expire
the queue. Otherwise we delete the group from service tree and group looses
its fair share.

So far I was marking a queue as wait_busy if it had consumed its slice and
it was last queue in the group. But this condition did not cover following
two cases.

1.If a request completed and slice has not expired yet. Next request comes
  in and is dispatched to disk. Now select_queue() hits and slice has expired.
  This group will be deleted. Because request is still in the disk, this queue
  will never get a chance to wait_busy.

2.If request completed and slice has not expired yet. Before next request
  comes in (delay due to think time), select_queue() hits and expires the
  queue hence group. This queue never got a chance to wait busy.

Gui was hitting the boundary condition 1 and not getting fairness numbers
proportional to weight.

This patch puts the checks for above two conditions and improves the fairness
numbers for sequential workload on rotational media. Check in select_queue()
takes care of case 1 and additional check in should_wait_busy() takes care
of case 2.

Reported-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-09 15:11:04 +01:00
..
blk-barrier.c block: allow large discard requests 2009-10-01 21:19:34 +02:00
blk-cgroup.c block: include linux/err.h to use ERR_PTR 2009-12-07 09:47:07 +01:00
blk-cgroup.h blkio: Implement dynamic io controlling policy registration 2009-12-04 16:38:14 +01:00
blk-core.c block: add helpers to run flush_dcache_page() against a bio and a request's pages 2009-11-26 09:16:19 +01:00
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: Fix io_context leak after failure of clone with CLONE_IO 2009-12-04 16:36:18 +01:00
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 block: Allow devices to indicate whether discarded blocks are zeroed 2009-12-03 09:24:48 +01:00
blk-softirq.c generic-ipi: remove CSD_FLAG_WAIT 2009-02-25 14:13:44 +01:00
blk-sysfs.c block: Allow devices to indicate whether discarded blocks are zeroed 2009-12-03 09:24:48 +01:00
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 block: jiffies fixes 2009-11-11 13:47:45 +01:00
cfq-iosched.c cfq-iosched: Take care of corner cases of group losing share due to deletion 2009-12-09 15:11:04 +01:00
compat_ioctl.c block: Allow devices to indicate whether discarded blocks are zeroed 2009-12-03 09:24:48 +01:00
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: Expose discard granularity 2009-11-10 11:50:21 +01:00
ioctl.c block: Allow devices to indicate whether discarded blocks are zeroed 2009-12-03 09:24:48 +01:00
Kconfig blkio: Some debugging aids for CFQ 2009-12-03 19:28:52 +01:00
Kconfig.iosched blkio: Allow CFQ group IO scheduling even when CFQ is a module 2009-12-04 16:38:14 +01:00
Makefile blkio: Introduce blkio controller cgroup interface 2009-12-03 19:28:51 +01:00
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