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Davide Sapienza f6c3ca0e58 block, bfq: prevent soft_rt_next_start from being stuck at infinity 
BFQ can deem a bfq_queue as soft real-time only if the queue
- periodically becomes completely idle, i.e., empty and with
  no still-outstanding I/O request;
- after becoming idle, gets new I/O only after a special reference
  time soft_rt_next_start.

In this respect, after commit "block, bfq: consider also past I/O in
soft real-time detection", the value of soft_rt_next_start can never
decrease. This causes a problem with the following special updating
case for soft_rt_next_start: to prevent queues that are not completely
idle to be wrongly detected as soft real-time (when they become
non-empty again), soft_rt_next_start is temporarily set to infinity
for empty queues with still outstanding I/O requests. But, if such an
update is actually performed, then, because of the above commit,
soft_rt_next_start will be stuck at infinity forever, and the queue
will have no more chance to be considered soft real-time.

On slow systems, this problem does cause actual soft real-time
applications to be occasionally not detected as such.

This commit addresses this issue by eliminating the pushing of
soft_rt_next_start to infinity, and by changing the way non-empty
queues are prevented from being wrongly detected as soft
real-time. Simply, a queue that becomes non-empty again can now be
detected as soft real-time only if it has no outstanding I/O request.

Signed-off-by: Davide Sapienza <sapienza.dav@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
 		2018-05-31 08:54:41 -06:00
..
partitions partitions/msdos: Unable to mount UFS 44bsd partitions 2018-01-10 09:12:16 -07:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig.iosched License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
badblocks.c badblocks: fix wrong return value in badblocks_set if badblocks are disabled 2017-11-03 11:29:50 -07:00
bfq-cgroup.c block: use ktime_get_ns() instead of sched_clock() for cfq and bfq 2018-05-09 08:33:06 -06:00
bfq-iosched.c block, bfq: prevent soft_rt_next_start from being stuck at infinity 2018-05-31 08:54:41 -06:00
bfq-iosched.h block, bfq: remove slow-system class 2018-05-31 08:54:38 -06:00
bfq-wf2q.c block, bfq: limit sectors served with interactive weight raising 2018-01-18 08:21:37 -07:00
bio-integrity.c block: Convert bio_set to mempool_init() 2018-05-14 13:16:03 -06:00
bio.c block: Drop bioset_create() 2018-05-30 15:33:32 -06:00
blk-cgroup.c blkcg: init root blkcg_gq under lock 2018-04-19 08:51:59 -06:00
blk-core.c block: convert bounce, q->bio_split to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
blk-exec.c blk-mq-sched: remove unused 'can_block' arg from blk_mq_sched_insert_request 2018-01-17 09:49:21 -07:00
blk-flush.c blk-mq: don't allocate driver tag upfront for flush rq 2017-11-04 12:40:13 -06:00
blk-integrity.c block drivers/block: Use octal not symbolic permissions 2018-05-24 13:38:59 -06:00
blk-ioc.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
blk-lib.c block: break discard submissions into the user defined size 2018-05-08 15:10:44 -06:00
blk-map.c Merge branch 'for-4.16/block' of git://git.kernel.dk/linux-block 2018-01-29 11:51:49 -08:00
blk-merge.c block: convert bounce, q->bio_split to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
blk-mq-cpumap.c blk-mq: don't keep offline CPUs mapped to hctx 0 2018-04-10 08:38:46 -06:00
blk-mq-debugfs.c blk-mq: Remove generation seqeunce 2018-05-29 08:59:21 -06:00
blk-mq-debugfs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
blk-mq-pci.c blk-mq: Allow PCI vector offset for mapping queues 2018-03-27 21:25:36 -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: abstract out blk-mq-sched rq list iteration bio merge helper 2018-05-30 10:43:58 -06:00
blk-mq-sched.h blk-mq-sched: remove unused 'can_block' arg from blk_mq_sched_insert_request 2018-01-17 09:49:21 -07:00
blk-mq-sysfs.c block drivers/block: Use octal not symbolic permissions 2018-05-24 13:38:59 -06:00
blk-mq-tag.c blk-mq: only iterate over inflight requests in blk_mq_tagset_busy_iter 2018-05-30 11:31:34 -06:00
blk-mq-tag.h Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block 2017-11-14 15:32:19 -08:00
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: simplify blk_mq_rq_timed_out 2018-05-29 08:59:21 -06:00
blk-mq.h blk-mq: Remove generation seqeunce 2018-05-29 08:59:21 -06:00
blk-settings.c block: Introduce blk_queue_flag_{set,clear,test_and_{set,clear}}() 2018-03-08 14:13:48 -07:00
blk-softirq.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
blk-stat.c block: consolidate struct request timestamp fields 2018-05-09 08:33:09 -06:00
blk-stat.h block: consolidate struct request timestamp fields 2018-05-09 08:33:09 -06:00
blk-sysfs.c block: convert bounce, q->bio_split to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
blk-tag.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
blk-throttle.c blk-throttle: return proper bool type to caller instead of 0/1 2018-05-30 12:48:22 -06:00
blk-timeout.c block: remove BLK_EH_HANDLED 2018-05-29 08:59:21 -06:00
blk-wbt.c block: get rid of struct blk_issue_stat 2018-05-09 08:33:05 -06:00
blk-wbt.h block: get rid of struct blk_issue_stat 2018-05-09 08:33:05 -06:00
blk-zoned.c blkdev_report_zones_ioctl(): Use vmalloc() to allocate large buffers 2018-05-22 11:58:07 -06:00
blk.h block: consolidate struct request timestamp fields 2018-05-09 08:33:09 -06:00
bounce.c block: fixup bioset_integrity_create() call 2018-05-30 18:51:21 -06:00
bsg-lib.c block: remove parent device reference from struct bsg_class_device 2018-05-29 13:00:25 -06:00
bsg.c block: remove parent device reference from struct bsg_class_device 2018-05-29 13:00:25 -06:00
cfq-iosched.c block drivers/block: Use octal not symbolic permissions 2018-05-24 13:38:59 -06:00
cmdline-parser.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
compat_ioctl.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
deadline-iosched.c block drivers/block: Use octal not symbolic permissions 2018-05-24 13:38:59 -06:00
elevator.c block: Document scheduler modification locking requirements 2018-01-18 12:54:42 -07:00
genhd.c block drivers/block: Use octal not symbolic permissions 2018-05-24 13:38:59 -06:00
ioctl.c block: pass inclusive 'lend' parameter to truncate_inode_pages_range 2018-02-23 15:20:19 -07:00
ioprio.c block: Add fallthrough markers to switch statements 2017-06-21 11:46:07 -06:00
kyber-iosched.c block: kyber: make kyber more friendly with merging 2018-05-30 10:47:40 -06:00
mq-deadline.c block drivers/block: Use octal not symbolic permissions 2018-05-24 13:38:59 -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: don't print a message when the device went away 2018-05-29 08:59:21 -06:00
scsi_ioctl.c block: consistently use GFP_NOIO instead of __GFP_NORECLAIM 2018-05-14 08:55:18 -06:00
sed-opal.c for-4.17/block-20180402 2018-04-05 14:27:02 -07:00
t10-pi.c t10-pi: Move opencoded contants to common header 2017-07-03 16:56:25 -06:00