linux-kernel - Re: [PATCH 0/5] perf: add support for capturing skid IP

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Date:   Thu, 15 Jun 2017 12:35:39 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "mingo@...e.hu" <mingo@...e.hu>,
        "Liang, Kan" <kan.liang@...el.com>, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH 0/5] perf: add support for capturing skid IP

On Thu, Jun 15, 2017 at 10:23 AM, Andi Kleen <ak@...ux.intel.com> wrote:
> On Thu, Jun 15, 2017 at 09:44:07AM -0700, Stephane Eranian wrote:
>> On Thu, Jun 15, 2017 at 8:10 AM, Andi Kleen <ak@...ux.intel.com> wrote:
>> > On Thu, Jun 15, 2017 at 06:56:24AM -0700, Stephane Eranian wrote:
>> >> This patchs adds a new sample record type called
>> >> PERF_SAMPLE_SKID_IP. The goal is to record
>> >> the unmodified interrupted instruction pointer (IP) as seen by
>> >> the kernel and reflected in the machine state.
>> >
>> > Patches look reasonable for me.
>> >
>> > If you only cared about branches it would be more natural to model
>> > it like a 1 entry LBR. That would make a lot more tooling work
>> > automatically.
>> >
>> You'd still have to modify tooling to present correct column headers.
>
> Why? It's from/to?
>
Ah, yes you are right, but it is not clear to me how you would specify
this cleanly with the interface.
Especially in the case where this could be used for non-branch instructions.

> -Andi