linux-kernel - Re: [PATCH v4 00/16] perf, persistent: Add persistent events

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Date:	Fri, 9 May 2014 12:17:22 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Robert Richter <rric@...nel.org>
Cc:	Jean Pihet <jean.pihet@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>
Subject: Re: [PATCH v4 00/16] perf, persistent: Add persistent events

On Wed, May 07, 2014 at 07:01:55PM +0200, Robert Richter wrote:
> I am fine with a fixed size. But this design might not be changable in
> the future without breaking the API. So its worth to think about this.
> Maybe we allow the process also to create the buffer, there are 2
> variants then:
> 
>  perf_event_open(...);
>  mmap(..., fd, ...);
>  ioctl(fd, set_persistent, 1);   /* Use existing buffer. */
>  close();
> 
>  fd = perf_event_open(...);
>  ioctl(fd, set_persistent, 1);   /* Create buffer with default size. */
>  close();
> 
> This would solve the problem how we adjust buffer size.
> 
> This requires a way to detect buffer size. See my mail how this could
> be done.

Yep, this makes sense and fits nicely with the perf interface so
persistent buffer sizes will be established at event creation.

This is all fine then.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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