linux-kernel - Re: [PATCH v3 4/5] perf/record: add documentation for sampling skid ip

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Date:   Wed, 8 Nov 2017 19:42:28 -0800
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,
        "Liang, Kan" <kan.liang@...el.com>, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH v3 4/5] perf/record: add documentation for sampling skid ip

On Wed, Nov 8, 2017 at 12:56 PM, Andi Kleen <ak@...ux.intel.com> wrote:
>> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
>> index 5a626ef666c2..3b156fa03c99 100644
>> --- a/tools/perf/Documentation/perf-record.txt
>> +++ b/tools/perf/Documentation/perf-record.txt
>> @@ -57,6 +57,14 @@ OPTIONS
>>                        FP mode, "dwarf" for DWARF mode, "lbr" for LBR mode and
>>                        "no" for disable callgraph.
>>         - 'stack-size': user stack size for dwarf mode
>> +       - 'skid_ip' : boolean, captures the unmodified interrupt instruction pointer
>> +                     (IP) in each sample. Usually with event-based sampling, the IP
>> +                     has skid and rarely point to the instruction which caused the
>> +                     event to overflow. On some architectures, the hardware can eliminate
>> +                     the skid and perf_events returns it as the IP with precise sampling is
>> +                     enabled. But for certain measurements, it may be useful to have both
>> +                     the correct and skid ip. This option enable capturing the skid ip in
>> +                     additional to the corrected ip. Default is: false
>
> Actually in the scanner you use 'skid-ip' (with minus). Documentation should at least match
> the scanner.
>
I have fixed the documentation. I used - because many other terms and
options use - instead of _.

> _ is usually safer than -
>
I tend to agree with you.

> -Andi