linux-kernel - Re: [PATCH v2 4/4] perf/x86/intel/pt: Opportunistically use single range output mode

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Message-ID: <87blu5ggpx.fsf@ashishki-desk.ger.corp.intel.com>
Date:   Fri, 25 Oct 2019 15:19:38 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        jolsa@...hat.com, adrian.hunter@...el.com,
        mathieu.poirier@...aro.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH v2 4/4] perf/x86/intel/pt: Opportunistically use single range output mode

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

> On Tue, Oct 22, 2019 at 12:58:12PM +0300, Alexander Shishkin wrote:
>> Most of PT implementations support Single Range Output mode, which is
>> an alternative to ToPA that can be used for a single contiguous buffer
>> and if we don't require an interrupt, that is, in AUX snapshot mode.
>> 
>> Now that perf core will use high order allocations for the AUX buffer,
>> in many cases the first condition will also be satisfied.
>> 
>> The two most obvious benefits of the Single Range Output mode over the
>> ToPA are:
>>  * not having to allocate the ToPA table(s),
>>  * not using the ToPA walk hardware.
>> 
>> Make use of this functionality where available and appropriate.
>
> This seems independent of the snapshot stuff, right?

Yes, it depends on the previous PT driver patch for context,
though. I'll drop it from the set.

Regards,
--
Alex