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| author |   Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2019-06-09 14:14:36 +0300 |
|---|---|---|
| committer |   Jonathan Corbet <corbet@lwn.net> | 2019-06-14 14:46:43 -0600 |
| commit | 9d9b889540c380d8f56f7a79edbaae2fff8684d1 (patch) | |
| tree | 8763e2124944139c266c77a2c9c53869724e9547 /Documentation/iostats.txt | |
| parent | Documentation/stackprotector: powerpc supports stack protector (diff) | |
| download | linux-dev-9d9b889540c380d8f56f7a79edbaae2fff8684d1.tar.xz linux-dev-9d9b889540c380d8f56f7a79edbaae2fff8684d1.zip | |
block: document iostat changes for disk busy time accounting
Since commit 5b18b5a73760 ("block: delete part_round_stats and switch to
less precise counting") io_ticks is approximated by adding one at each
start and end of requests if jiffies has changed.
This works perfectly for requests shorter than a jiffy. If requests runs
more than 2 jiffies some I/O time will not be accounted unless there are
other reuqests.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/iostats.txt')
| -rw-r--r-- | Documentation/iostats.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/iostats.txt b/Documentation/iostats.txt index 49df45f90e8a..5d63b18bd6d1 100644 --- a/Documentation/iostats.txt +++ b/Documentation/iostats.txt @@ -97,6 +97,10 @@ Field 9 -- # of I/Os currently in progress Field 10 -- # of milliseconds spent doing I/Os This field increases so long as field 9 is nonzero. + Since 5.0 this field counts jiffies when at least one request was + started or completed. If request runs more than 2 jiffies then some + I/O time will not be accounted unless there are other requests. + Field 11 -- weighted # of milliseconds spent doing I/Os This field is incremented at each I/O start, I/O completion, I/O merge, or read of these stats by the number of I/Os in progress |