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

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Message-ID: <20191024135632.GE4114@hirez.programming.kicks-ass.net>
Date:   Thu, 24 Oct 2019 15:56:32 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
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
Subject: Re: [PATCH v2 4/4] perf/x86/intel/pt: Opportunistically use single
 range output mode

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?