linux/Documentation/ABI/testing/procfs-diskstats
Michael Callahan bdca3c87fb block: Track DISCARD statistics and output them in stat and diskstat
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: Michael Callahan <michaelcallahan@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andy Newell <newella@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-18 08:44:22 -06:00

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What: /proc/diskstats
Date: February 2008
Contact: Jerome Marchand <jmarchan@redhat.com>
Description:
The /proc/diskstats file displays the I/O statistics
of block devices. Each line contains the following 14
fields:
1 - major number
2 - minor mumber
3 - device name
4 - reads completed successfully
5 - reads merged
6 - sectors read
7 - time spent reading (ms)
8 - writes completed
9 - writes merged
10 - sectors written
11 - time spent writing (ms)
12 - I/Os currently in progress
13 - time spent doing I/Os (ms)
14 - weighted time spent doing I/Os (ms)
Kernel 4.18+ appends four more fields for discard
tracking putting the total at 18:
15 - discards completed successfully
16 - discards merged
17 - sectors discarded
18 - time spent discarding
For more details refer to Documentation/iostats.txt