From: David Ahern <dsahern@gmail.com>
To: Peipei Wang <wangpeipei.90@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>,
perf group <linux-perf-users@vger.kernel.org>
Subject: Re: How can I get timestamps of samples in perf
Date: Sat, 10 Aug 2013 11:01:30 -0400 [thread overview]
Message-ID: <520655CA.1020504@gmail.com> (raw)
In-Reply-To: <CAEuYUeo9KnMpfU2s9cqvNJG5dY+4925rMpcEK-AhjoaNNcU_XA@mail.gmail.com>
On 8/10/13 10:34 AM, Peipei Wang wrote:
> I get it. Is the timestamp for wall-clock or not??? What is the
> counting unit of timestamp? Seconds??
It is a "perf_clock" timestamp in seconds.micro-seconds. On x86 the
timestamp is related to the TSC -- usually.
I have been on a 2-1/2 year mission and counting to get time-of-day
correlations into perf. e.g., see
https://github.com/dsahern/linux/tree/perf-time-of-day-3.8.
That branch has a kernel side change to add an ioctl to pull the
perf_clock timestamp into userspace. It does not include tracepoints to
catch ntpd updates for example.
David
>
> swapper 0 [000] 1591103.081337: instructions: c1022ae6 int
> swapper 0 [000] 1591103.081341: instructions: c1022ae6 int
> swapper 0 [000] 1591103.081343: instructions: c1022ae6 int
> swapper 0 [000] 1591103.081345: instructions: c1022ae6 int
> swapper 0 [000] 1591103.081348: instructions: c1036a26 __t
> swapper 0 [000] 1591103.081353: cycles: c1035e68 native_wr
> swapper 0 [000] 1591103.081355: cycles: c1035e68 native_wr
> swapper 0 [000] 1591103.081357: cycles: c1035e68 native_wr
> swapper 0 [000] 1591103.081359: cycles: c1035e68 native_wr
> swapper 0 [000] 1591103.081362: cycles: c101909c mwait_id
>
prev parent reply other threads:[~2013-08-10 15:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-10 2:35 How can I get timestamps of samples in perf Peipei Wang
2013-08-10 4:43 ` Andi Kleen
2013-08-10 14:34 ` Peipei Wang
2013-08-10 15:01 ` David Ahern [this message]
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