linux/block
Ming Lei 358a3a6bcc blk-mq: don't handle TAG_SHARED in restart
Now restart is used in the following cases, and TAG_SHARED is for
SCSI only.

1) .get_budget() returns BLK_STS_RESOURCE
- if resource in target/host level isn't satisfied, this SCSI device
will be added in shost->starved_list, and the whole queue will be rerun
(via SCSI's built-in RESTART) in scsi_end_request() after any request
initiated from this host/targe is completed. Forget to mention, host level
resource can't be an issue for blk-mq at all.

- the same is true if resource in the queue level isn't satisfied.

- if there isn't outstanding request on this queue, then SCSI's RESTART
can't work(blk-mq's can't work too), and the queue will be run after
SCSI_QUEUE_DELAY, and finally all starved sdevs will be handled by SCSI's
RESTART when this request is finished

2) scsi_dispatch_cmd() returns BLK_STS_RESOURCE
- if there isn't onprogressing request on this queue, the queue
will be run after SCSI_QUEUE_DELAY

- otherwise, SCSI's RESTART covers the rerun.

3) blk_mq_get_driver_tag() failed
- BLK_MQ_S_TAG_WAITING covers the cross-queue RESTART for driver
allocation.

In one word, SCSI's built-in RESTART is enough to cover the queue
rerun, and we don't need to pay special attention to TAG_SHARED wrt. restart.

In my test on scsi_debug(8 luns), this patch improves IOPS by 20% ~ 30% when
running I/O on these 8 luns concurrently.

Aslo Roman Pen reported the current RESTART is very expensive especialy
when there are lots of LUNs attached in one host, such as in his
test, RESTART causes half of IOPS be cut.

Fixes: https://marc.info/?l=linux-kernel&m=150832216727524&w=2
Fixes: 6d8c6c0f97 ("blk-mq: Restart a single queue if tag sets are shared")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-11-01 08:20:33 -06:00
..
partitions partitions/ldm: switch to use uuid_t 2017-06-05 16:59:14 +02:00
badblocks.c block: Add fallthrough markers to switch statements 2017-06-21 11:46:07 -06:00
bfq-cgroup.c bfq: Declare local functions static 2017-09-01 13:56:37 -06:00
bfq-iosched.c block, bfq: fix unbalanced decrements of burst size 2017-10-09 09:54:58 -06:00
bfq-iosched.h Merge branch 'for-4.14/block' of git://git.kernel.dk/linux-block 2017-09-07 11:59:42 -07:00
bfq-wf2q.c block, bfq: guarantee update_next_in_service always returns an eligible entity 2017-08-31 08:20:31 -06:00
bio-integrity.c block: remove unnecessary NULL checks in bioset_integrity_free() 2017-10-06 13:03:12 -06:00
bio.c block: fix Sphinx kernel-doc warning 2017-10-16 13:00:12 -06:00
blk-cgroup.c blkcg: check pol->cpd_free_fn before free cpd 2017-10-10 09:04:47 -06:00
blk-core.c block: Fix a race between blk_cleanup_queue() and timeout handling 2017-10-30 13:28:10 -06:00
blk-exec.c block: introduce new block status code type 2017-06-09 09:27:32 -06:00
blk-flush.c block: update comments to reflect REQ_FLUSH -> REQ_PREFLUSH rename 2017-08-25 10:36:54 -06:00
blk-integrity.c block: switch bios to blk_status_t 2017-06-09 09:27:32 -06:00
blk-ioc.c Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-03-03 10:53:35 -08:00
blk-lib.c block: cope with WRITE ZEROES failing in blkdev_issue_zeroout() 2017-10-25 12:28:23 -06:00
blk-map.c blk-map: call blk_queue_bounce from blk_rq_append_bio 2017-06-27 12:13:21 -06:00
blk-merge.c block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
blk-mq-cpumap.c blk-mq: map queues to all present CPUs 2017-07-24 10:01:31 -06:00
blk-mq-debugfs.c block: remove QUEUE_FLAG_STACKABLE 2017-10-05 15:22:59 -06:00
blk-mq-debugfs.h mq-deadline: add debugfs attributes 2017-05-04 08:25:17 -06:00
blk-mq-pci.c blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL 2017-08-18 08:08:14 -06:00
blk-mq-rdma.c block: Add rdma affinity based queue mapping helper 2017-08-08 14:58:03 -04:00
blk-mq-sched.c blk-mq: don't handle TAG_SHARED in restart 2017-11-01 08:20:33 -06:00
blk-mq-sched.h blk-mq: introduce .get_budget and .put_budget in blk_mq_ops 2017-11-01 08:20:02 -06:00
blk-mq-sysfs.c blk-mq: untangle debugfs and sysfs 2017-05-04 08:24:13 -06:00
blk-mq-tag.c blk-mq: Make blk_mq_reinit_tagset() calls easier to read 2017-08-18 08:36:58 -06:00
blk-mq-tag.h blk-mq-tag: kill unused tag enums 2017-10-01 01:26:21 -06:00
blk-mq-virtio.c blk-mq: provide a default queue mapping for virtio device 2017-02-27 20:54:05 +02:00
blk-mq.c blk-mq-sched: improve dispatching from sw queue 2017-11-01 08:20:02 -06:00
blk-mq.h blk-mq-sched: improve dispatching from sw queue 2017-11-01 08:20:02 -06:00
blk-settings.c block: Warn if blk_queue_rq_timed_out() is called for a blk-mq queue 2017-08-23 12:02:30 -06:00
blk-softirq.c smp: Avoid using two cache lines for struct call_single_data 2017-08-29 15:14:38 +02:00
blk-stat.c blk-stat: delete useless code 2017-10-10 13:48:14 -06:00
blk-stat.h blk-stat: kill blk_stat_rq_ddir() 2017-04-21 07:56:23 -06:00
blk-sysfs.c block: fix warning when I/O elevator is changed as request_queue is being removed 2017-08-28 10:52:44 -06:00
blk-tag.c block: Unexport blk_queue_end_tag() 2017-08-18 08:36:58 -06:00
blk-throttle.c blk-throttle: fix null pointer dereference while throttling writeback IOs 2017-10-10 13:09:34 -06:00
blk-timeout.c block: Fix a race between blk_cleanup_queue() and timeout handling 2017-10-30 13:28:10 -06:00
blk-wbt.c block,bfq: Disable writeback throttling 2017-10-09 08:29:21 -06:00
blk-wbt.h block: Make writeback throttling defaults consistent for SQ devices 2017-04-19 08:49:03 -06:00
blk-zoned.c block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
blk.h blk-mq: document the need to have STARTED and COMPLETED share a byte 2017-10-04 11:22:24 -06:00
bounce.c block: remove the queue_bounce_pfn helper 2017-06-27 12:13:45 -06:00
bsg-lib.c bsg-lib: don't free job in bsg_prepare_job 2017-09-25 08:56:05 -06:00
bsg.c bsg: remove #if 0'ed code 2017-08-29 10:50:30 -06:00
cfq-iosched.c block/cfq: cache rightmost rb_node 2017-09-08 18:26:49 -07:00
cmdline-parser.c block: remove unrelated header files and export symbol 2014-01-21 20:18:26 -08:00
compat_ioctl.c compat_hdio_ioctl: Fix a declaration 2017-08-31 17:32:41 -04:00
deadline-iosched.c block, scheduler: convert xxx_var_store to void 2017-08-28 10:01:08 -06:00
elevator.c elevator: allow name aliases 2017-10-25 12:36:50 -06:00
genhd.c Merge branch 'for-4.14/block' of git://git.kernel.dk/linux-block 2017-09-07 11:59:42 -07:00
ioctl.c block: move CAP_SYS_ADMIN check in blkdev_roset() 2017-10-25 12:25:00 -06:00
ioprio.c block: Add fallthrough markers to switch statements 2017-06-21 11:46:07 -06:00
Kconfig block: Add rdma affinity based queue mapping helper 2017-08-08 14:58:03 -04:00
Kconfig.iosched block, bfq: add full hierarchical scheduling and cgroups support 2017-04-19 08:30:26 -06:00
kyber-iosched.c block: kyber: check if there are requests in ctx in kyber_has_work() 2017-11-01 08:20:02 -06:00
Makefile block: Add rdma affinity based queue mapping helper 2017-08-08 14:58:03 -04:00
mq-deadline.c mq-deadline: add 'deadline' as a name alias 2017-10-25 12:36:55 -06:00
noop-iosched.c block: move existing elevator ops to union 2017-01-17 10:03:33 -07:00
opal_proto.h block: sed-opal: Set MBRDone on S3 resume path if TPER is MBREnabled 2017-09-11 09:45:52 -06:00
partition-generic.c block: fix a crash caused by wrong API 2017-09-25 08:56:05 -06:00
scsi_ioctl.c block: Change argument type of scsi_req_init() 2017-06-20 19:27:14 -06:00
sed-opal.c block: sed-opal: Set MBRDone on S3 resume path if TPER is MBREnabled 2017-09-11 09:45:52 -06:00
t10-pi.c t10-pi: Move opencoded contants to common header 2017-07-03 16:56:25 -06:00