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From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Mike Galbraith <efault@gmx.de>, Paul Mackerras <paulus@samba.org>,
        Stephane Eranian <eranian@google.com>, Andi Kleen <ak@linux.intel.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Matt Fleming <matt.fleming@intel.com>
Subject: Re: [PATCH v1 03/11] perf: Allow for multiple ring buffers per event
In-Reply-To: <20140508124121.GU11096@twins.programming.kicks-ass.net>
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Date: Thu, 08 May 2014 15:46:36 +0300
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Peter Zijlstra <peterz@infradead.org> writes:

> On Thu, May 08, 2014 at 03:34:17PM +0300, Alexander Shishkin wrote:
>> Peter Zijlstra <peterz@infradead.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