Re: [PATCH 3/5] uclampset: Add man page

[Vincent Guittot <vincent.guittot@linaro.org>]

On Sat, 16 Jan 2021 at 20:11, Qais Yousef <qais.yousef@arm.com> wrote:
>
> Signed-off-by: Qais Yousef <qais.yousef@arm.com>
> ---
>  schedutils/uclampset.1 | 169 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 169 insertions(+)
>  create mode 100644 schedutils/uclampset.1
>
> diff --git a/schedutils/uclampset.1 b/schedutils/uclampset.1
> new file mode 100644
> index 000000000..1a525458a
> --- /dev/null
> +++ b/schedutils/uclampset.1
> @@ -0,0 +1,169 @@
> +.\" uclampset(1) manpage
> +.\"
> +.\" Copyright (C) 2020 Qais Yousef <qais.yousef@arm.com>
> +.\" Copyright (C) 2020 Arm Ltd
> +.\"
> +.\" This is free documentation; you can redistribute it and/or
> +.\" modify it under the terms of the GNU General Public License,
> +.\" version 2, as published by the Free Software Foundation.
> +.\"
> +.\" The GNU General Public License's references to "object code"
> +.\" and "executables" are to be interpreted as the output of any
> +.\" document formatting or typesetting system, including
> +.\" intermediate and printed output.
> +.\"
> +.\" This manual is distributed in the hope that it will be useful,
> +.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
> +.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +.\" GNU General Public License for more details.
> +.\"
> +.\" You should have received a copy of the GNU General Public License along
> +.\" with this program; if not, write to the Free Software Foundation, Inc.,
> +.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> +.\"
> +.TH UCLAMPSET 1 "August 2020" "util-linux" "User Commands"
> +.SH NAME
> +uclampset \- manipulate the utilization clamping attributes of the system or
> +a process.
> +.SH SYNOPSIS
> +.B uclampset
> +[options]
> +.RI [ -m\ uclamp_min ]\ [ -M\ uclamp_max ]\ command\  [ argument ...]
> +.br
> +.B uclampset
> +[options]
> +.RI [ -m\ uclamp_min ]\ [ -M\ uclamp_max ]
> +.B \-p
> +.RI pid
> +.SH DESCRIPTION
> +.B uclampset
> +sets or retrieves the utilization clamping attributes of an existing \fIpid\fR,
> +or runs \fIcommand\fR with the given attributes.
> +
> +Utilization clamping is a new feature added in v5.3. It gives a hint to the
> +scheduler about the allowed range of utilization the task should be operating
> +at.
> +
> +The utilization of the task affects frequency selection and task placement.
> +Only schedutil cpufreq governor understands handling util clamp hints at the
> +time of writing. Consult your kernel docs for further info about other
> +cpufreq governors support.
> +
> +If you're running on asymmetric heterogeneous system like Arm's big.LITTLE.
> +Utilization clamping can help bias task placement. If the task is boosted such
> +that
> +.BR util_min
> +value is higher than the little cores' capacity, then the scheduler will do its
> +best to place it on a big core.
> +
> +Similarly, if
> +.BR util_max
> +is smaller than or equal the capacity of the little cores, then the scheduler
> +can still choose to place it there even if the actual utilization of the task
> +is at max.
> +
> +Setting a task's
> +.B uclamp_min
> +to a none zero value  will effectively boost the task as when it runs it'll
> +always start from this utilization value.
> +
> +By setting a task's
> +.B uclamp_max
> +below 1024, this will effectively cap the task as when it runs it'll never be
> +able to go above this utilization value.
> +
> +The full utilization range is: [0:1024].
> +
> +.SH OPTIONS
> +.TP
> +.BR \-m
> +Set util_min value.
> +.TP
> +.BR \-M
> +Set util_max value.
> +.TP
> +.BR \-a ,\  \-\-all-tasks
> +Set or retrieve the utilization clamping attributes of all the tasks (threads)
> +for a given PID.
> +.TP
> +.BR \-s ,\  \-\-system
> +Set or retrieve the system-wide utilization clamping attributes.
> +.TP
> +.BR \-\-max
> +Show minimum and maximum valid utilization values, then exit.
> +.TP
> +.BR \-p ,\  \-\-pid
> +Operate on an existing PID and do not launch a new task.
> +.TP
> +.BR \-v ,\  \-\-verbose
> +Show status information.
> +.TP
> +.BR \-V ,\  \-\-version
> +Display version information and exit.
> +.TP
> +.BR \-h ,\  \-\-help
> +Display help text and exit.
> +.SH USAGE
> +.TP
> +The default behavior is to run a new command:
> +.B uclampset
> +.I [-m\ uclamp_min]
> +.I [-M\ uclamp_max]
> +.IR command\  [ arguments ]
> +.TP
> +You can also retrieve the utilization clamping attributes of an existing task:
> +.B uclampset \-p
> +.I pid
> +.TP
> +Or set them:
> +.B uclampset \-p
> +.I pid
> +.I [-m\ uclamp_min]
> +.I [-M\ uclamp_max]
> +.TP
> +Or control the system-wide attributes:
> +.B uclampset \-s
> +.I [-m\ uclamp_min]
> +.I [-M\ uclamp_max]
> +.SH PERMISSIONS
> +A user must possess
> +.B CAP_SYS_NICE
> +to change the scheduling attributes of a process.  Any user can retrieve the
> +scheduling information.
> +
> +.SH NOTES
> +The system wide utilization clamp attributes are there to control the _allowed_
> +range the tasks can use. By default both
> +.BR uclamp_min
> +and
> +.BR uclamp_max
> +are set to 1024. This means users can set the utilization clamp values for
> +their task across the full range [0:1024].
> +
> +.TP
> +For example:
> +.B uclampset \-s
> +.I -m\ 512
> +.I -M\ 700
> +.PP
> +will prevent any task from being boosted higher than 512. And all tasks in the

will prevent any task from being boosted higher than 700
or
will ensure  any task to be boosted higher than 512


> +systems are capped to a utilization of 700. Effectively rendering the maximum
> +performance of the system to 700.
> +
> +Consult your kernel docs for the exact expected behavior on that kernel.
> +.SH AUTHORS
> +.UR qais.yousef@arm.com
> +Qais Yousef
> +.UE
> +.SH SEE ALSO
> +.BR nice (1),
> +.BR renice (1),
> +.BR taskset (1),
> +.BR sched (7)
> +.sp
> +See
> +.BR sched_setscheduler (2)
> +for a description of the Linux scheduling scheme.
> +.SH AVAILABILITY
> +The uclampset command is part of the util-linux package and is available from
> +https://www.kernel.org/pub/linux/utils/util-linux/.
> --
> 2.25.1
>