linux-kernel - Re: [PATCH 1/2] perf_event_open.2: Document PERF_EVENT_IOC_PAUSE

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Date:   Sat, 22 Oct 2016 12:02:55 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Wang Nan <wangnan0@...wei.com>
Cc:     mtk.manpages@...il.com, pi3orama@....com,
        linux-kernel@...r.kernel.org, linux-man@...r.kernel.org,
        lizefan@...wei.com, vincent.weaver@...ne.edu
Subject: Re: [PATCH 1/2] perf_event_open.2: Document
 PERF_EVENT_IOC_PAUSE_OUTPUT

Hello Wang Nan

Thanks for this patch! A few comments below.

On 10/21/2016 01:38 PM, Wang Nan wrote:
> Linux 4.7 (86e7972f690c1017fd086cdfe53d8524e68c661c) introduces
> PERF_EVENT_IOC_PAUSE_OUTPUT feature. Document it.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Michael Kerrisk <mtk.manpages@...il.com>
> ---
>  man2/perf_event_open.2 | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
> index fade28c..2d3acad 100644
> --- a/man2/perf_event_open.2
> +++ b/man2/perf_event_open.2
> @@ -2865,7 +2865,18 @@ The argument is a BPF program file descriptor that was created by
>  a previous
>  .BR bpf (2)
>  system call.
> -.SS Using prctl(2)
> +.TP
> +.BR PERF_EVENT_IOC_PAUSE_OUTPUT " (since Linux 4.7)"
> +.\" commit 86e7972f690c1017fd086cdfe53d8524e68c661c
> +This allows pausing and resuming the event's ring-buffer. A
> +paused ring-buffer does not prevent samples generation, but simply

s/samples generation/generation of samples/

> +discards them. The discarded samples are considered lost, causes

s/them/the samples/

s/causes/causing/

> +.BR PERF_RECORD_LOST
> +to be generated when possible.
> +
> +The argument is an integer. Nonzero value pauses the ring-buffer,

s/Nonzero/a nonzero/

> +zero value resumes the ring-buffer.

s/zero value/zero/

> +.SS Using prctl

As noted by Vince, the change to this SS line should not be part of this patch.

>  A process can enable or disable all the event groups that are
>  attached to it using the
>  .BR prctl (2)

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/