Commit bdca3c87 authored by Michael Callahan's avatar Michael Callahan Committed by Jens Axboe
Browse files

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: default avatarMichael Callahan <michaelcallahan@fb.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Andy Newell <newella@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent ddcf35d3

Documentation/ABI/testing/procfs-diskstats

+10 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 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
@@ -19,4 +20,13 @@ Description: 
		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

Documentation/block/stat.txt

+16 −12
Original line number Diff line number Diff line
@@ -31,28 +31,32 @@ write ticks milliseconds total wait time for write requests 
in_flight       requests      number of I/Os currently in flight

io_ticks        milliseconds  total time this block device has been active

time_in_queue   milliseconds  total wait time for all requests

discard I/Os    requests      number of discard I/Os processed

discard merges  requests      number of discard I/Os merged with in-queue I/O

discard sectors sectors       number of sectors discarded

discard ticks   milliseconds  total wait time for discard requests



read I/Os, write I/Os

=====================

read I/Os, write I/Os, discard I/0s

===================================



These values increment when an I/O request completes.



read merges, write merges

=========================

read merges, write merges, discard merges

=========================================



These values increment when an I/O request is merged with an

already-queued I/O request.



read sectors, write sectors

===========================

read sectors, write sectors, discard_sectors

============================================



These values count the number of sectors read from or written to this

block device.  The "sectors" in question are the standard UNIX 512-byte

sectors, not any device- or filesystem-specific block size.  The

counters are incremented when the I/O completes.

These values count the number of sectors read from, written to, or

discarded from this block device.  The "sectors" in question are the

standard UNIX 512-byte sectors, not any device- or filesystem-specific

block size.  The counters are incremented when the I/O completes.



read ticks, write ticks

=======================

read ticks, write ticks, discard ticks

======================================



These values count the number of milliseconds that I/O requests have

waited on this block device.  If there are multiple I/O requests waiting,

Documentation/iostats.txt

+15 −0
Original line number Diff line number Diff line
@@ -31,6 +31,9 @@ Here are examples of these different formats:: 
      3    0   hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160

      3    1   hda1 35486 38030 38030 38030



   4.18+ diskstats:

      3    0   hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160 0 0 0 0



On 2.4 you might execute ``grep 'hda ' /proc/partitions``. On 2.6+, you have

a choice of ``cat /sys/block/hda/stat`` or ``grep 'hda ' /proc/diskstats``.
@@ -101,6 +104,18 @@ Field 11 -- weighted # of milliseconds spent doing I/Os 
    last update of this field.  This can provide an easy measure of both

    I/O completion time and the backlog that may be accumulating.



Field 12 -- # of discards completed

    This is the total number of discards completed successfully.



Field 13 -- # of discards merged

    See the description of field 2



Field 14 -- # of sectors discarded

    This is the total number of sectors discarded successfully.



Field 15 -- # of milliseconds spent discarding

    This is the total number of milliseconds spent by all discards (as

    measured from __make_request() to end_that_request_last()).



To avoid introducing performance bottlenecks, no locks are held while

modifying these counters.  This implies that minor inaccuracies may be

block/genhd.c

+10 −3
Original line number Diff line number Diff line
@@ -1333,8 +1333,11 @@ static int diskstats_show(struct seq_file *seqf, void *v) 
		part_round_stats(gp->queue, cpu, hd);

		part_stat_unlock();

		part_in_flight(gp->queue, hd, inflight);

		seq_printf(seqf, "%4d %7d %s %lu %lu %lu "

			   "%u %lu %lu %lu %u %u %u %u\n",

		seq_printf(seqf, "%4d %7d %s "

			   "%lu %lu %lu %u "

			   "%lu %lu %lu %u "

			   "%u %u %u "

			   "%lu %lu %lu %u\n",

			   MAJOR(part_devt(hd)), MINOR(part_devt(hd)),

			   disk_name(gp, hd->partno, buf),

			   part_stat_read(hd, ios[STAT_READ]),
@@ -1347,7 +1350,11 @@ static int diskstats_show(struct seq_file *seqf, void *v) 
			   jiffies_to_msecs(part_stat_read(hd, ticks[STAT_WRITE])),

			   inflight[0],

			   jiffies_to_msecs(part_stat_read(hd, io_ticks)),

			   jiffies_to_msecs(part_stat_read(hd, time_in_queue))

			   jiffies_to_msecs(part_stat_read(hd, time_in_queue)),

			   part_stat_read(hd, ios[STAT_DISCARD]),

			   part_stat_read(hd, merges[STAT_DISCARD]),

			   part_stat_read(hd, sectors[STAT_DISCARD]),

			   jiffies_to_msecs(part_stat_read(hd, ticks[STAT_DISCARD]))

			);

	}

	disk_part_iter_exit(&piter);

block/partition-generic.c

+7 −2
Original line number Diff line number Diff line
@@ -131,6 +131,7 @@ ssize_t part_stat_show(struct device *dev, 
		"%8lu %8lu %8llu %8u "

		"%8lu %8lu %8llu %8u "

		"%8u %8u %8u "

		"%8lu %8lu %8llu %8u"

		"\n",

		part_stat_read(p, ios[STAT_READ]),

		part_stat_read(p, merges[STAT_READ]),
@@ -142,7 +143,11 @@ ssize_t part_stat_show(struct device *dev, 
		jiffies_to_msecs(part_stat_read(p, ticks[STAT_WRITE])),

		inflight[0],

		jiffies_to_msecs(part_stat_read(p, io_ticks)),

		jiffies_to_msecs(part_stat_read(p, time_in_queue)));

		jiffies_to_msecs(part_stat_read(p, time_in_queue)),

		part_stat_read(p, ios[STAT_DISCARD]),

		part_stat_read(p, merges[STAT_DISCARD]),

		(unsigned long long)part_stat_read(p, sectors[STAT_DISCARD]),

		jiffies_to_msecs(part_stat_read(p, ticks[STAT_DISCARD])));

}



ssize_t part_inflight_show(struct device *dev, struct device_attribute *attr,

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