From: David Ahern <dsahern@gmail.com>
To: Bernie Pope <bjpope@unimelb.edu.au>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: What is the source of the time field in perf_sample events?
Date: Fri, 06 Apr 2012 11:14:44 -0600 [thread overview]
Message-ID: <4F7F2484.2020307@gmail.com> (raw)
In-Reply-To: <B76DE0C2-3A2B-4D77-BBA2-9157891B222D@unimelb.edu.au>
On 3/18/12 6:08 AM, Bernie Pope wrote:
> Hello,
>
> I'm writing a tool to parse the perf.data output of perf and was wondering about the source of the timestamps found in perf_sample events? Specifically I mean the u64 time field in the perf_sample struct in util/event.h. I believe it is in nanoseconds from a particular event (system start?), but I can't find any documentation about where the time comes from.
>
> I'm also interested in reading from this time source from a userspace program, is that possible?
Did you get a response to this?
Code wise, you'll need to follow perf_clock(). I believe for x86 with a
stable TSC you end up in native_sched_clock() in arch/x86/kernel/tsc.c.
As for the corresponding userspace call I believe it is
clock_gettime(CLOCK_MONOTONIC, ...).
David
prev parent reply other threads:[~2012-04-06 17:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-18 12:08 What is the source of the time field in perf_sample events? Bernie Pope
2012-04-06 17:14 ` David Ahern [this message]
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