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Re: [patch 07/11] perf_event_open.2: 4.1 add AUX_FLAG_OVERWRITE support

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  Re: [patch 07/11] perf_event_open.2: 4.1 add AUX_FLAG_OVERWRITE support "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2015-10-14 08:40 +0200

#1246333 — Re: [patch 07/11] perf_event_open.2: 4.1 add AUX_FLAG_OVERWRITE support

On 07/23/2015 07:13 PM, Vince Weaver wrote:
> 
> This manpage patch relates to the addition of the AUX sample flag
> AUX_FLAG_OVERWRITE as added in the following commit:

Thanks, Vince. Applied.

Cheers,

Michael



> 	commit 2023a0d2829e521fe6ad6b9907f3f90bfbf57142
> 	Author: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> 
> 	perf: Support overwrite mode for the AUX area
> 
> 	Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> 	Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> 	Cc: Borislav Petkov <bp@alien8.de>
> 	Cc: Frederic Weisbecker <fweisbec@gmail.com>
> 	Cc: H. Peter Anvin <hpa@zytor.com>
> 	Cc: Kaixu Xia <kaixu.xia@linaro.org>
> 	Cc: Linus Torvalds <torvalds@linux-foundation.org>
> 	Cc: Mike Galbraith <efault@gmx.de>
> 	Cc: Paul Mackerras <paulus@samba.org>
> 	Cc: Robert Richter <rric@kernel.org>
> 	Cc: Stephane Eranian <eranian@google.com>
> 	Cc: Thomas Gleixner <tglx@linutronix.de>
> 	Cc: acme@infradead.org
> 	Cc: adrian.hunter@intel.com
> 	Cc: kan.liang@intel.com
> 	Cc: markus.t.metzger@intel.com
> 	Cc: mathieu.poirier@linaro.org
> 	Link: http://lkml.kernel.org/r/1421237903-181015-9-git-send-email-alexander.shishkin@linux.intel.com
> 	Signed-off-by: Ingo Molnar <mingo@kernel.org>
> 
> Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
> 
> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
> index dfb0b64..238eb62 100644
> --- a/man2/perf_event_open.2
> +++ b/man2/perf_event_open.2
> @@ -1670,6 +1670,15 @@ rlimit as well as the
>  .I perf_event_mlock_kb
>  allowance.
>  
> +By default the AUX buffer will be truncated if it will not fit
> +in the available space in the ring buffer.
> +If the AUX buffer is mapped as a read only buffer, then it will
> +operate in ring buffer mode where old data will be overwritten
> +by new.
> +In overwrite mode it might not be possible to infer where the
> +new data began, and it is the consumer's job to disable
> +measurement while reading to avoid possible data races.
> +
>  The
>  .IR aux_head " and " aux_tail
>  ring buffer pointers have the same behavior and ordering
> @@ -2476,6 +2485,10 @@ describes the aux update.
>  .B PERF_AUX_FLAG_TRUNCATED
>  if set then the data returned was truncated to fit the available
>  buffer size.
> +.TP
> +.B PERF_AUX_FLAG_OVERWRITE
> +.\" commit 2023a0d2829e521fe6ad6b9907f3f90bfbf57142
> +if set then the data returned has overwritten previous data.
>  .RE
>  .RE
>  .RE
> 


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