[PATCH] prctl.2, proc.5: proposal to reflect http://lwn.net/Articles/484162

[PATCH] prctl.2, proc.5: proposal to reflect http://lwn.net/Articles/484162

[Dmitry Antipov]

Document PR_GET_TIMERSLACK and PR_SET_TIMERSLACK for prctl (2).
Document /proc/sys/kernel/timer_slack for proc (5).

Signed-off-by: Dmitry Antipov <dmitry.antipov-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 man2/prctl.2 |   15 +++++++++++++++
 man5/proc.5  |    4 ++++
 2 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/man2/prctl.2 b/man2/prctl.2
index effad2a..dcf803f 100644
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -378,6 +378,21 @@ Return the current per-process machine check kill policy.
 All unused
 .BR prctl ()
 arguments must be zero.
+.TP
+.BR PR_GET_TIMERSLACK " (since Linux 2.6.28)"
+Return the current per-thread high-resolution timers slack, in nanoseconds.
+.TP
+.BR PR_SET_TIMERSLACK " (since Linux 2.6.28)"
+Set the current per-thread high-resolution timers slack. If arg2 is less than or
+equal to zero, system-wide default value is restored. The system-wide default can
+be read and set by /proc/sys/kernel/timer_slack (see
+.BR proc (5)).
+Otherwise, if arg2 is less than or equal to HRTIMER_MAX_SLACK (which is a kernel
+constant defined in include/linux/hrtimer.h), this value is set up as a new slack.
+Slack is not inherited across
+.BR fork (2);
+new process initially uses system-wide default slack, and new thread inherits
+it's slack from the group leader.
 .SH "RETURN VALUE"
 On success,
 .BR PR_GET_DUMPABLE ,
diff --git a/man5/proc.5 b/man5/proc.5
index 54ccdd8..0493b6b 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -2407,6 +2407,10 @@ date behind it indicates the time the kernel was built.
 This file specifies the system-wide limit on the number of
 threads (tasks) that can be created on the system.
 .TP
+.IR /proc/sys/kernel/timer_slack
+This file specifies the system-wide default slack for
+high-resolution timers, in nanoseconds.
+.TP
 .IR /proc/sys/kernel/zero-paged " (PowerPC only) "
 This file
 contains a flag.
-- 
1.7.7.6

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Re: [PATCH] prctl.2, proc.5: proposal to reflect http://lwn.net/Articles/484162

[Michael Kerrisk (man-pages)]

Dmitry,

Thanks for this patch. Would you be willing to revise it a little to
add some words about the *purpose* of timer slack.

Thanks

Michael


On Fri, Apr 6, 2012 at 9:02 PM, Dmitry Antipov
<dmitry.antipov-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> Document PR_GET_TIMERSLACK and PR_SET_TIMERSLACK for prctl (2).
> Document /proc/sys/kernel/timer_slack for proc (5).
>
> Signed-off-by: Dmitry Antipov <dmitry.antipov-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
>  man2/prctl.2 |   15 +++++++++++++++
>  man5/proc.5  |    4 ++++
>  2 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/man2/prctl.2 b/man2/prctl.2
> index effad2a..dcf803f 100644
> --- a/man2/prctl.2
> +++ b/man2/prctl.2
> @@ -378,6 +378,21 @@ Return the current per-process machine check kill policy.
>  All unused
>  .BR prctl ()
>  arguments must be zero.
> +.TP
> +.BR PR_GET_TIMERSLACK " (since Linux 2.6.28)"
> +Return the current per-thread high-resolution timers slack, in nanoseconds.
> +.TP
> +.BR PR_SET_TIMERSLACK " (since Linux 2.6.28)"
> +Set the current per-thread high-resolution timers slack. If arg2 is less than or
> +equal to zero, system-wide default value is restored. The system-wide default can
> +be read and set by /proc/sys/kernel/timer_slack (see
> +.BR proc (5)).
> +Otherwise, if arg2 is less than or equal to HRTIMER_MAX_SLACK (which is a kernel
> +constant defined in include/linux/hrtimer.h), this value is set up as a new slack.
> +Slack is not inherited across
> +.BR fork (2);
> +new process initially uses system-wide default slack, and new thread inherits
> +it's slack from the group leader.
>  .SH "RETURN VALUE"
>  On success,
>  .BR PR_GET_DUMPABLE ,
> diff --git a/man5/proc.5 b/man5/proc.5
> index 54ccdd8..0493b6b 100644
> --- a/man5/proc.5
> +++ b/man5/proc.5
> @@ -2407,6 +2407,10 @@ date behind it indicates the time the kernel was built.
>  This file specifies the system-wide limit on the number of
>  threads (tasks) that can be created on the system.
>  .TP
> +.IR /proc/sys/kernel/timer_slack
> +This file specifies the system-wide default slack for
> +high-resolution timers, in nanoseconds.
> +.TP
>  .IR /proc/sys/kernel/zero-paged " (PowerPC only) "
>  This file
>  contains a flag.
> --
> 1.7.7.6
>



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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