linux/block, branch v2.6.32.1

cfq-iosched: limit coop preemption

2009-11-03T19:25:02Z

CFQ has an optimization for cooperated applications. if several io-context have close requests, they will get boost. But the optimization get abused. Considering thread a, b, which work on one file. a reads sectors s, s+2, s+4, ...; b reads sectors s+1, s+3, s +5, ... Both a and b are sequential read, so they can open idle window. a reads a sector s and goes to idle window and wakeup b. b reads sector s+1, since in current implementation, cfq_should_preempt() thinks a and b are cooperators, b will preempt a. b then reads sector s+1 and goes to idle window and wakeup a. for the same reason, a will preempt b and reads s+2. a and b will continue the circle. The circle will be very long, and a and b will occupy whole disk queue. Other applications will nearly have no chance to run. Fix this limiting coop preempt until a queue is scheduled normally again. Signed-off-by: Shaohua Li Acked-by: Jeff Moyer Signed-off-by: Jens Axboe

cfq-iosched: fix bad return value cfq_should_preempt()

2009-11-03T19:21:35Z

Commit a6151c3a5c8e1ff5a28450bc8d6a99a2a0add0a7 inadvertently reversed a preempt condition check, potentially causing a performance regression. Make the meta check correct again. Signed-off-by: Jens Axboe

block: silently error unsupported empty barriers too

2009-10-24T12:14:31Z

With 2.6.32-rc5 in a KVM guest using dm and virtio_blk, we see the following errors: end_request: I/O error, dev vda, sector 0 end_request: I/O error, dev vda, sector 0 The errors go away if dm stops submitting empty barriers, by reverting: commit 52b1fd5a27c625c78373e024bf570af3c9d44a79 Author: Mikulas Patocka dm: send empty barriers to targets in dm_flush We should silently error all barriers, even empty barriers, on devices like virtio_blk which don't support them. See also: https://bugzilla.redhat.com/514901 Signed-off-by: Mark McLoughlin Signed-off-by: Mike Snitzer Acked-by: Alasdair G Kergon Acked-by: Mikulas Patocka Cc: Rusty Russell Cc: Neil Brown Cc: Christoph Hellwig Signed-off-by: Jens Axboe

blk-settings: fix function parameter kernel-doc notation

2009-10-12T06:20:47Z

Fix kernel-doc notation in blk-settings.c::blk_queue_max_discard_sectors(). Signed-off-by: Randy Dunlap Signed-off-by: Jens Axboe

elv_iosched_store(): fix strstrip() misuse

2009-10-09T06:48:08Z

elv_iosched_store() ignore the return value of strstrip(). It makes small inconsistent behavior. This patch fixes it. ==================================== # cd /sys/block/{blockdev}/queue case1: # echo "anticipatory" > scheduler # cat scheduler noop [anticipatory] deadline cfq case2: # echo "anticipatory " > scheduler # cat scheduler noop [anticipatory] deadline cfq case3: # echo " anticipatory" > scheduler bash: echo: write error: Invalid argument ==================================== # cd /sys/block/{blockdev}/queue case1: # echo "anticipatory" > scheduler # cat scheduler noop [anticipatory] deadline cfq case2: # echo "anticipatory " > scheduler # cat scheduler noop [anticipatory] deadline cfq case3: # echo " anticipatory" > scheduler noop [anticipatory] deadline cfq Cc: Li Zefan Cc: Jens Axboe Signed-off-by: KOSAKI Motohiro Signed-off-by: Jens Axboe

cfq-iosched: avoid probable slice overrun when idling

2009-10-08T06:43:32Z

If the average think time is larger than the remaining time slice for any given queue, don't allow it to idle. A succesful idle also means that we need to dispatch and complete a request, so if we don't even have time left for the idle process, we would overrun the slice in any case. Signed-off-by: Corrado Zoccolo Signed-off-by: Jens Axboe

cfq-iosched: apply bool value where we return 0/1

2009-10-07T18:02:57Z

Saves 16 bytes of text, woohoo. But the more important point is that it makes the code more readable when returning bool for 0/1 cases. Signed-off-by: Jens Axboe

cfq-iosched: fix think time allowed for seekers

2009-10-07T17:51:54Z

CFQ enables idle only for processes that think less than the allowed idle time. Since idle time is lower for seeky queues, we should use the correct value in the comparison. Signed-off-by: Corrado Zoccolo Signed-off-by: Jens Axboe

cfq-iosched: fix the slice residual sign

2009-10-06T19:09:32Z

We should subtract the slice residual from the rb tree key, since a negative residual count indicates that the cfqq overran its slice the last time. Hence we want to add the overrun time, to position it a bit further away in the service tree. Reported-by: Corrado Zoccolo Signed-off-by: Jens Axboe

cfq-iosched: abstract out the 'may this cfqq dispatch' logic

2009-10-06T18:49:37Z

Makes the whole thing easier to read, cfq_dispatch_requests() was a bit messy before. Signed-off-by: Jens Axboe