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| author | Alejandro Colomar <alx@kernel.org> | 2023-08-17 22:47:16 +0200 |
|---|---|---|
| committer | Alejandro Colomar <alx@kernel.org> | 2023-08-17 23:12:31 +0200 |
| commit | 0569afbbccd6de28d1bacd13471a679ad2674aa1 (patch) | |
| tree | e0286e2d8dee88465fc9e2b31697573af0aa10cf /man5/proc_pid_io.5 | |
| parent | 29597f1e7ecd58e8239a1650c6bdea0517f913af (diff) | |
| parent | 92cdcec79df039146e5ed42cac23cd4b7e3f9e25 (diff) | |
| download | man-pages-0569afbbccd6.tar.gz | |
proc*.5: Make sashimi
[Merge tag 'proc-sashimi-v1' of <git://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git>]
proc(5) was a huge page, which was quite hard to maintain, extend, read,
and refer to. Split the page into small pages for the different
directories and files within /proc. Some pages are still too large
(e.g., proc_sys(5)), and will some day be split even more.
This split keeps the contents of the original page, without modifying
anything; not even the formatting.
The only thing that has been modified in this patches, is that
directories are consistently represented with a trailing slash.
For the file name of the pages, we've used the name of the interface
(e.g., /proc/pid/), removing the leading and trailing '/'s and then
translating the remaining ones as `tr / _` (e.g., proc_pid.5). The
title of the pages (TH) is consistent with this. The NAME of the pages,
however, is the actual path name of the interfaces.
The man page references have not been updated, as that was a more
complex and tedious work, so I expect that they'll be slowly updated as
we and users find out.
Link: <https://lore.kernel.org/linux-man/e3a5bc09-e835-9819-4aaa-12959495ac59@kernel.org/T/>
Acked-by: Oskari Pirhonen <xxc3ncoredxx@gmail.com>
Acked-by: Günther Noack <gnoack@google.com>
Acked-by: "G. Branden Robinson" <g.branden.robinson@gmail.com>
Cc: Brian Inglis <Brian.Inglis@Shaw.ca>
Cc: Ingo Schwarze <schwarze@usta.de>
Cc: Colin Watson <cjwatson@debian.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Diffstat (limited to 'man5/proc_pid_io.5')
| -rw-r--r-- | man5/proc_pid_io.5 | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/man5/proc_pid_io.5 b/man5/proc_pid_io.5 new file mode 100644 index 0000000000..1242523191 --- /dev/null +++ b/man5/proc_pid_io.5 @@ -0,0 +1,98 @@ +.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com> +.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com> +.\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org> +.\" +.\" SPDX-License-Identifier: GPL-3.0-or-later +.\" +.TH proc_pid_io 5 (date) "Linux man-pages (unreleased)" +.SH NAME +/proc/pid/io \- I/O statistics +.SH DESCRIPTION +.TP +.IR /proc/ pid /io " (since Linux 2.6.20)" +.\" commit 7c3ab7381e79dfc7db14a67c6f4f3285664e1ec2 +This file contains I/O statistics for the process, for example: +.IP +.in +4n +.EX +.RB "#" " cat /proc/3828/io" +rchar: 323934931 +wchar: 323929600 +syscr: 632687 +syscw: 632675 +read_bytes: 0 +write_bytes: 323932160 +cancelled_write_bytes: 0 +.EE +.in +.IP +The fields are as follows: +.RS +.TP +.IR rchar ": characters read" +The number of bytes which this task has caused to be read from storage. +This is simply the sum of bytes which this process passed to +.BR read (2) +and similar system calls. +It includes things such as terminal I/O and +is unaffected by whether or not actual +physical disk I/O was required (the read might have been satisfied from +pagecache). +.TP +.IR wchar ": characters written" +The number of bytes which this task has caused, or shall cause to be written +to disk. +Similar caveats apply here as with +.IR rchar . +.TP +.IR syscr ": read syscalls" +Attempt to count the number of read I/O operations\[em]that is, +system calls such as +.BR read (2) +and +.BR pread (2). +.TP +.IR syscw ": write syscalls" +Attempt to count the number of write I/O operations\[em]that is, +system calls such as +.BR write (2) +and +.BR pwrite (2). +.TP +.IR read_bytes ": bytes read" +Attempt to count the number of bytes which this process really did cause to +be fetched from the storage layer. +This is accurate for block-backed filesystems. +.TP +.IR write_bytes ": bytes written" +Attempt to count the number of bytes which this process caused to be sent to +the storage layer. +.TP +.IR cancelled_write_bytes : +The big inaccuracy here is truncate. +If a process writes 1 MB to a file and then deletes the file, +it will in fact perform no writeout. +But it will have been accounted as having caused 1 MB of write. +In other words: this field represents the number of bytes which this process +caused to not happen, by truncating pagecache. +A task can cause "negative" I/O too. +If this task truncates some dirty pagecache, +some I/O which another task has been accounted for +(in its +.IR write_bytes ) +will not be happening. +.RE +.IP +.IR Note : +In the current implementation, things are a bit racy on 32-bit systems: +if process A reads process B's +.IR /proc/ pid /io +while process B is updating one of these 64-bit counters, +process A could see an intermediate result. +.IP +Permission to access this file is governed by a ptrace access mode +.B PTRACE_MODE_READ_FSCREDS +check; see +.BR ptrace (2). +.SH SEE ALSO +.BR proc (5) |