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1b2ff19e6a
linux/block
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Jan Kara 1b2ff19e6a blk-flush: Queue through IO scheduler when flush not required 
Currently blk_insert_flush() just adds flush request to q->queue_head
when flush is not required. That completely bypasses IO scheduler so
e.g. CFQ can be idling waiting for new request to arrive and will idle
through the whole window unnecessarily. Luckily this only happens in
rare cases as usually checks in generic_make_request_checks() clear
FLUSH and FUA flags early if they are not needed.

When no flushing is actually required, we can easily fix the problem by
properly queueing the request through the IO scheduler. Ideally IO
scheduler should be also made aware of requests queued via
blk_flush_queue_rq(). However inserting flush request through IO
scheduler can have unwanted side-effects since due to flush batching
delaying the flush request in IO scheduler will delay all flush requests
possibly coming from other processes. So we keep adding the request
directly to q->queue_head.

Signed-off-by: Jan Kara <jack@suse.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-16 15:23:51 -07:00
..
partitions Merge branch 'for-3.20/core' of git://git.kernel.dk/linux-block 2015-02-12 14:13:23 -08:00
bio-integrity.c block: blk_flush_integrity() for bio-based drivers 2015-10-21 14:43:44 -06:00
bio.c mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd 2015-11-06 17:50:42 -08:00
blk-cgroup.c Merge branch 'for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2015-11-05 14:51:32 -08:00
blk-core.c block: fix blk-core.c kernel-doc warning 2015-11-11 09:36:57 -07:00
blk-exec.c block: move PM request support to IDE 2015-05-05 13:40:42 -06:00
blk-flush.c blk-flush: Queue through IO scheduler when flush not required 2015-11-16 15:23:51 -07:00
blk-integrity.c block, libnvdimm, nvme: provide a built-in blk_integrity nop profile 2015-10-21 14:43:45 -06:00
blk-ioc.c mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd 2015-11-06 17:50:42 -08:00
blk-iopoll.c Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next 2014-06-03 12:57:53 -07:00
blk-lib.c block: re-add discard_granularity and alignment checks 2015-10-28 09:12:58 +09:00
blk-map.c block: Copy a user iovec if it includes gaps 2015-09-11 09:03:50 -06:00
blk-merge.c block: avoid to merge splitted bio 2015-10-21 15:00:51 -06:00
blk-mq-cpu.c blk-mq: add file comments and update copyright notices 2014-05-28 10:15:41 -06:00
blk-mq-cpumap.c blk-mq: avoid inserting requests before establishing new mapping 2015-09-29 11:32:50 -06:00
blk-mq-sysfs.c block: add block polling support 2015-11-07 10:40:47 -07:00
blk-mq-tag.c mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd 2015-11-06 17:50:42 -08:00
blk-mq-tag.h blk-mq: factor out a helper to iterate all tags for a request_queue 2015-10-01 10:10:57 +02:00
blk-mq.c blk-mq: mark __blk_mq_complete_request() static 2015-11-11 09:36:56 -07:00
blk-mq.h blk-mq: mark __blk_mq_complete_request() static 2015-11-11 09:36:56 -07:00
blk-settings.c Merge branch 'for-4.3/core' of git://git.kernel.dk/linux-block 2015-09-02 13:10:25 -07:00
blk-softirq.c block: fix regression with block enabled tagging 2014-04-09 21:54:06 -06:00
blk-sysfs.c block: add block polling support 2015-11-07 10:40:47 -07:00
blk-tag.c block: support different tag allocation policy 2015-01-23 14:15:46 -07:00
blk-throttle.c cgroup: replace cgroup_on_dfl() tests in controllers with cgroup_subsys_on_dfl() 2015-09-18 11:56:28 -04:00
blk-timeout.c blk-mq: Allow requests to never expire 2015-01-08 08:59:01 -07:00
blk.h Merge branch 'for-4.4/integrity' of git://git.kernel.dk/linux-block 2015-11-04 20:51:48 -08:00
bounce.c Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2015-09-19 18:57:09 -07:00
bsg-lib.c bsg: Remove unused function bsg_goose_queue() 2012-12-06 14:33:02 +01:00
bsg.c block: Simplify bsg complete all 2015-02-04 09:57:52 -07:00
cfq-iosched.c cgroup: replace cgroup_on_dfl() tests in controllers with cgroup_subsys_on_dfl() 2015-09-18 11:56:28 -04:00
cmdline-parser.c block: remove unrelated header files and export symbol 2014-01-21 20:18:26 -08:00
compat_ioctl.c block, bdi: an active gendisk always has a request_queue associated with it 2014-09-08 10:00:35 -06:00
deadline-iosched.c block: Stop abusing csd.list for fifo_time 2014-02-24 14:46:32 -08:00
elevator.c block: check bio_mergeable() early before merging 2015-10-21 15:00:54 -06:00
genhd.c block: Inline blk_integrity in struct gendisk 2015-10-21 14:42:42 -06:00
ioctl.c block: add an API for Persistent Reservations 2015-10-21 14:46:56 -06:00
ioprio.c pidns: fix set/getpriority and ioprio_set/get in PRIO_USER mode 2015-11-06 17:50:42 -08:00
Kconfig block: Add T10 Protection Information functions 2014-09-27 09:14:59 -06:00
Kconfig.iosched blkcg: make CONFIG_BLK_CGROUP bool 2012-03-06 21:27:21 +01:00
Makefile block: Add T10 Protection Information functions 2014-09-27 09:14:59 -06:00
noop-iosched.c elevator: use list_{first,prev,next}_entry 2015-11-16 15:21:48 -07:00
partition-generic.c block: Inline blk_integrity in struct gendisk 2015-10-21 14:42:42 -06:00
scsi_ioctl.c mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM 2015-11-06 17:50:42 -08:00
t10-pi.c block: Consolidate static integrity profile properties 2015-10-21 14:42:38 -06:00