linux/block
Alireza Haghdoost 23779fbc99 block: Enable sysfs nomerge control for I/O requests in the plug list
This patch enables the sysfs to control I/O request merge
functionality in the plug list. While this control has been
implemented for the request queue, it was dismissed in the plug list.
Therefore, block layer merges requests together (or attempt to merge)
even if the merge capability was disable using sysfs nomerge parameter
value 2.

This limitation is directly affects functionality of io_submit()
system call. The system call enables user to submit a bunch of IO
requests from user space using struct iocb **ios input argument.
However, the unconditioned merging functionality in the plug list
potentially merges these requests together down the road. Therefore,
there is no way to distinguish between an application sending bunch of
sequential IOs and an application sending one big IO. Ultimately, all
requests generated by the former app merge within the plug list
together and looks similar to the second app.

While the merging functionality is a desirable feature to improve the
performance of IO subsystem for some applications, it is not useful
for other application like ours at all.

Signed-off-by: Alireza Haghdoost <alireza@cs.umn.edu>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>

Coding style modified.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2013-11-08 09:00:22 -07:00
..
partitions block/partitions/efi.c: treat size mismatch as a warning, not an error 2013-10-16 21:35:53 -07:00
blk-cgroup.c Merge branch 'for-3.12/core' of git://git.kernel.dk/linux-block 2013-09-22 15:00:11 -07:00
blk-cgroup.h cgroup: make css_for_each_descendant() and friends include the origin css in the iteration 2013-08-08 20:11:27 -04:00
blk-core.c block: Enable sysfs nomerge control for I/O requests in the plug list 2013-11-08 09:00:22 -07:00
blk-exec.c If the queue is dying then we only call the rq->end_io callout. 2013-09-18 08:33:55 -06:00
blk-flush.c Block: blk-flush: Fixed indent code style 2013-03-22 12:22:51 -06:00
blk-integrity.c scatterlist: introduce sg_unmark_end 2013-03-20 15:43:04 +10:30
blk-ioc.c lib/radix-tree.c: make radix_tree_node_alloc() work correctly within interrupt 2013-09-11 15:59:36 -07:00
blk-iopoll.c block: Replace __get_cpu_var uses 2013-11-08 08:59:58 -07:00
blk-lib.c block: account iowait time when waiting for completion of IO request 2013-02-15 16:45:07 +01:00
blk-map.c block: re-use existing 'reading' variable instead of checking direction again 2011-12-21 15:27:24 +01:00
blk-merge.c scatterlist: introduce sg_unmark_end 2013-03-20 15:43:04 +10:30
blk-settings.c block: properly stack underlying max_segment_size to DM device 2013-11-08 09:00:17 -07:00
blk-softirq.c block: Replace __get_cpu_var uses 2013-11-08 08:59:58 -07:00
blk-sysfs.c block/blk-sysfs.c: replace strict_strtoul() with kstrtoul() 2013-09-11 15:56:56 -07:00
blk-tag.c block: Reserve only one queue tag for sync IO if only 3 tags are available 2013-06-28 21:32:27 +02:00
blk-throttle.c cgroup: make css_for_each_descendant() and friends include the origin css in the iteration 2013-08-08 20:11:27 -04:00
blk-timeout.c block: fix race between request completion and timeout handling 2013-11-08 08:59:04 -07:00
blk.h block,elevator: use new hashtable implementation 2013-01-11 14:43:13 +01:00
bsg-lib.c bsg: Remove unused function bsg_goose_queue() 2012-12-06 14:33:02 +01:00
bsg.c hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
cfq-iosched.c Merge branch 'for-3.12/core' of git://git.kernel.dk/linux-block 2013-09-22 15:00:11 -07:00
cmdline-parser.c block: support embedded device command line partition 2013-09-11 15:56:57 -07:00
compat_ioctl.c kernel-wide: fix missing validations on __get/__put/__copy_to/__copy_from_user() 2013-09-11 15:58:18 -07:00
deadline-iosched.c block: Convert kmalloc_node(...GFP_ZERO...) to kzalloc_node(...) 2013-09-11 13:22:03 -06:00
elevator.c elevator: acquire q->sysfs_lock in elevator_change() 2013-11-08 09:00:13 -07:00
genhd.c block: Convert kmalloc_node(...GFP_ZERO...) to kzalloc_node(...) 2013-09-11 13:22:03 -06:00
ioctl.c Merge branch 'for-3.7/core' of git://git.kernel.dk/linux-block 2012-10-11 09:04:23 +09:00
Kconfig block: change config option name for cmdline partition parsing 2013-09-30 14:31:02 -07:00
Kconfig.iosched blkcg: make CONFIG_BLK_CGROUP bool 2012-03-06 21:27:21 +01:00
Makefile block: change config option name for cmdline partition parsing 2013-09-30 14:31:02 -07:00
noop-iosched.c elevator: Fix a race in elevator switching 2013-07-03 13:25:24 +02:00
partition-generic.c Revert "loop: cleanup partitions when detaching loop device" 2013-04-08 10:12:11 +02:00
scsi_ioctl.c aio: don't include aio.h in sched.h 2013-05-07 20:16:25 -07:00