Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
Enhanced partition statistics: documentation update
Update the documentation to reflect the change in userspace interface.
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
authored by Jerome Marchand and committed by Jens Axboe 0e53c2be c3c930d9
+22
Documentation/ABI/testing/procfs-diskstats
+22
Documentation/ABI/testing/procfs-diskstats
···
1
+
What: /proc/diskstats
2
+
Date: February 2008
3
+
Contact: Jerome Marchand <jmarchan@redhat.com>
4
+
Description:
5
+
The /proc/diskstats file displays the I/O statistics
6
+
of block devices. Each line contains the following 14
7
+
fields:
8
+
1 - major number
9
+
2 - minor mumber
10
+
3 - device name
11
+
4 - reads completed succesfully
12
+
5 - reads merged
13
+
6 - sectors read
14
+
7 - time spent reading (ms)
15
+
8 - writes completed
16
+
9 - writes merged
17
+
10 - sectors written
18
+
11 - time spent writing (ms)
19
+
12 - I/Os currently in progress
20
+
13 - time spent doing I/Os (ms)
21
+
14 - weighted time spent doing I/Os (ms)
22
+
For more details refer to Documentation/iostats.txt
+28
Documentation/ABI/testing/sysfs-block
+28
Documentation/ABI/testing/sysfs-block
···
1
+
What: /sys/block/<disk>/stat
2
+
Date: February 2008
3
+
Contact: Jerome Marchand <jmarchan@redhat.com>
4
+
Description:
5
+
The /sys/block/<disk>/stat files displays the I/O
6
+
statistics of disk <disk>. They contain 11 fields:
7
+
1 - reads completed succesfully
8
+
2 - reads merged
9
+
3 - sectors read
10
+
4 - time spent reading (ms)
11
+
5 - writes completed
12
+
6 - writes merged
13
+
7 - sectors written
14
+
8 - time spent writing (ms)
15
+
9 - I/Os currently in progress
16
+
10 - time spent doing I/Os (ms)
17
+
11 - weighted time spent doing I/Os (ms)
18
+
For more details refer Documentation/iostats.txt
19
+
20
+
21
+
What: /sys/block/<disk>/<part>/stat
22
+
Date: February 2008
23
+
Contact: Jerome Marchand <jmarchan@redhat.com>
24
+
Description:
25
+
The /sys/block/<disk>/<part>/stat files display the
26
+
I/O statistics of partition <part>. The format is the
27
+
same as the above-written /sys/block/<disk>/stat
28
+
format.
+14
-1
Documentation/iostats.txt
+14
-1
Documentation/iostats.txt
···
58
58
Each set of stats only applies to the indicated device; if you want
59
59
system-wide stats you'll have to find all the devices and sum them all up.
60
60
61
-
Field 1 -- # of reads issued
61
+
Field 1 -- # of reads completed
62
62
This is the total number of reads completed successfully.
63
63
Field 2 -- # of reads merged, field 6 -- # of writes merged
64
64
Reads and writes which are adjacent to each other may be merged for
···
131
131
words, the number of reads for partitions is counted slightly before time
132
132
of queuing for partitions, and at completion for whole disks. This is
133
133
a subtle distinction that is probably uninteresting for most cases.
134
+
135
+
More significant is the error induced by counting the numbers of
136
+
reads/writes before merges for partitions and after for disks. Since a
137
+
typical workload usually contains a lot of successive and adjacent requests,
138
+
the number of reads/writes issued can be several times higher than the
139
+
number of reads/writes completed.
140
+
141
+
In 2.6.25, the full statistic set is again available for partitions and
142
+
disk and partition statistics are consistent again. Since we still don't
143
+
keep record of the partition-relative address, an operation is attributed to
144
+
the partition which contains the first sector of the request after the
145
+
eventual merges. As requests can be merged across partition, this could lead
146
+
to some (probably insignificant) innacuracy.
134
147
135
148
Additional notes
136
149
----------------