Indeed tool iostat's await is not good enough, which is somewhat sketchy
and could not show request's latency on device driver's side.

Here we add a new counter to track io request's d2c time, also with this
patch, we can extend iostat to show this value easily.

Note:
I had checked how iostat is implemented, it just reads fields it needs,
so iostat won't be affected by this change, so does tsar.
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

Add tracking of REQ_OP_DISCARD ios to the partition statistics and
append them to the various stat files in /sys as well as
/proc/diskstats.  These are tracked with the same four stats as reads
and writes:

Number of discard ios completed.
Number of discard ios merged
Number of discard sectors completed
Milliseconds spent on discard requests

This is done via adding a new STAT_DISCARD define to genhd.h and then
using it to index that stat field for discard requests.

tj: Refreshed on top of v4.17 and other previous updates.
Signed-off-by: NMichael Callahan <michaelcallahan@fb.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Andy Newell <newella@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Everything there that it is said for 2.6 also applies on
current 4.x Kernels. So, update the information there.

While here, use ``foo`` for literals.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:

- promote main title level;
- mark literal blocks as such;
- Add blank lines to avoid Sphinx errors.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

iostats.txt has a merged description of fields 2 and 6, but it's not obvious.
This patch adds a field 6, pointing to the merged description of field 6 in
field 2.
Signed-off-by: NDavid Hilton <david.hilton.p@gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

- correction that disk stats values are native-word-sized
  32-bit or 64-bit values, not always 32-bi values
- drop "Last modified" entry; use git for that
- fix a few typos
- change "cpu" to "CPU"
Reported-by: NLinda Walsh <lkml@tlinx.org>
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

fix "is increases", drop "is"
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Update the documentation to reflect the change in userspace interface.
Signed-off-by: NJerome Marchand <jmarchan@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Some of the code has been gradually transitioned to using the proper
struct request_queue, but there's lots left. So do a full sweet of
the kernel and get rid of this typedef and replace its uses with
the proper type.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!