From: Peter Zijlstra <peterz@infradead.org>
To: Drew Richardson <drew.richardson@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
John Stultz <john.stultz@linaro.org>,
Wade Cherry <Wade.Cherry@arm.com>,
Pawel Moll <pawel.moll@arm.com>
Subject: Re: [PATCH] ftrace: Provide trace clock monotonic raw
Date: Mon, 4 May 2015 22:57:48 +0200 [thread overview]
Message-ID: <20150504205748.GB21418@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150504200515.GA24626@dreric01-Precision-T1650>
On Mon, May 04, 2015 at 01:05:19PM -0700, Drew Richardson wrote:
> I'm collecting and merging data from perf, with Android Atrace data
> (writes to /sys/kernel/debug/tracing/trace_marker) which ends up in
> the ftrace stream and other measurements collected from
> userspace. Currently the only clock readable from userspace, supported
> by perf and by ftrace is CLOCK_MONOTONIC. However this clock is
> affected by the incremental adjustments performed by adjtime(3) and
> NTP.
Which should not matter at all, right? If both sources are using the
same clock (they are) then its trivial to merge them and everything
works as expected.
> But I'd prefer to use a clock that is advancing at a consistent
> rate, hence CLOCK_MONOTONIC_RAW.
Right, Mathieu is asking _why_ you prefer that?
next prev parent reply other threads:[~2015-05-04 20:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-04 14:41 Drew Richardson
2015-05-04 15:10 ` Mathieu Desnoyers
2015-05-04 20:05 ` Drew Richardson
2015-05-04 20:47 ` John Stultz
2015-05-04 20:57 ` Peter Zijlstra [this message]
2015-05-05 14:54 ` Drew Richardson
2015-05-08 0:42 ` Steven Rostedt
2015-05-08 1:27 ` Mathieu Desnoyers
2015-05-08 14:09 ` Steven Rostedt
2015-05-08 14:29 ` Drew Richardson
2015-05-08 14:30 ` [PATCHv3] " Drew Richardson
2015-05-08 14:41 ` Steven Rostedt
2015-05-08 16:05 ` John Stultz
2015-05-08 16:15 ` Steven Rostedt
2015-05-08 16:21 ` John Stultz
2015-05-08 16:11 ` Peter Zijlstra
2015-05-12 14:26 ` Thomas Gleixner
2015-05-12 19:59 ` Steven Rostedt
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