linux-kernel - Re: [PATCH 4/8] perf data: Add a 'perf' prefix to the generic fields

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Date:	Thu, 11 Dec 2014 12:47:30 -0700
From:	David Ahern <dsahern@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org
CC:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jeremie Galarneau <jgalar@...icios.com>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Tom Zanussi <tzanussi@...il.com>
Subject: Re: [PATCH 4/8] perf data: Add a 'perf' prefix to the generic fields

On 12/11/14 11:57 AM, Sebastian Andrzej Siewior wrote:
>>>     $ babeltrace ./ctf-data/
>>>     [03:19:13.962131936] (+0.000001935) cycles: { }, { perf_ip =
>>> 0xFFFFFFFF8105443A, perf_tid = 20714, perf_pid = 20714, perf_period = 8 }
>>>     [03:19:13.962133732] (+0.000001796) cycles: { }, { perf_ip =
>>> 0xFFFFFFFF8105443A, perf_tid = 20714, perf_pid = 20714, perf_period =
>>> 114 }
>>>     ...
>>
>> How is babeltrace showing time-of-day for perf-based data files? Is that
>> tod when the command is run?
>
> CTF needs an a base offset which we set to 0 because we don't have it.
> It then takes the NS timestamp and computes the "time".

so the perf-clock timestamp is converted to hour-min-second-nsec. That 
is even more confusing - for me at least.

By base offset you mean the conversion between perf-clock and realtime? 
What if that information is known (e.g., my tree at 
https://github.com/dsahern/linux as time-of-day support through a klm) - 
what's the ctf function to set the base offset? Can it be changed as a 
file is processed - e.g., tracepoints capturing ntp adjustments?

David
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