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

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Message-ID: <CABPqkBTb3w3Cvz2hxpe2ZF_DLgsHrF+fMPTrT4OQwU=gatg7tA@mail.gmail.com>
Date:   Thu, 15 Jun 2017 09:44:07 -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 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.
It is mostly interesting for branches for sure but any situation where you
want to skidless IP and the skid IP would work because they tell you
something about the sampled instruction.