linux-kernel - Re: [PATCH v1 03/11] perf: Allow for multiple ring buffers per event

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Message-ID: <87ha50cuab.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Thu, 08 May 2014 15:46:36 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v1 03/11] perf: Allow for multiple ring buffers per event

Peter Zijlstra <peterz@...radead.org> writes:

> On Thu, May 08, 2014 at 03:34:17PM +0300, Alexander Shishkin wrote:
>> Peter Zijlstra <peterz@...radead.org> writes:
>> 
>> > So the aux_head/tail values should also be in the file space and not
>> > start at 0 again, similar for the offsets in the AUX record.
>> 
>> Thinking some more about it: if we keep aux_{offset,size} in userpg,
>> then it would make sense to have aux_{head,tail} run from 0 to infinity
>> similar to data_{head,tail}, especially considering that neither data_*
>> nor aux_* pointers are file offsets anyway.
>
> Yeah, this might make it easier. So then the rule is *_offset +
> *_{head,tail} is the actual file offset into the buffer.

You mean *_offset + (*_{head,tail} % *_size) ?

Regards,
--
Alex
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