From: David Ahern <dsahern-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>,
Namhyung Kim <namhyung-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Richard Cochran
<richardcochran-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>,
Arnaldo Carvalho de Melo
<acme-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
John Stultz <john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH v2 1/2] perf: Add sampling of the raw monotonic clock
Date: Fri, 26 Sep 2014 13:25:08 -0600 [thread overview]
Message-ID: <5425BD94.4030006@gmail.com> (raw)
In-Reply-To: <1411743959.3852.45.camel@hornet>
On 9/26/14, 9:05 AM, Pawel Moll wrote:
> To do the correlation you need both timestamps to be "taken"
> simultaneously:
>
> perf event user event
> -----O--------------+-------------O------> t_mono
> : | :
> : V :
> -----O----------------------------O------> t_perf
>
> Of course it's not possible get both values literally at the same time,
> but placing them in a atomic context a couple of instructions from each
> other still gives pretty good results. The larger this distance is, the
An early patchset on this topic added the realtime clock as an event and
an ioctl was used to push a sample into the event stream. In that case
you have wall clock and perf-clock samples taken in the same kernel
context and about as close together as you can get.
https://lkml.org/lkml/2011/2/27/158
https://lkml.org/lkml/2011/2/27/159
David
WARNING: multiple messages have this Message-ID (diff)
From: David Ahern <dsahern@gmail.com>
To: Pawel Moll <pawel.moll@arm.com>, Namhyung Kim <namhyung@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Paul Mackerras <paulus@samba.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
John Stultz <john.stultz@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] perf: Add sampling of the raw monotonic clock
Date: Fri, 26 Sep 2014 13:25:08 -0600 [thread overview]
Message-ID: <5425BD94.4030006@gmail.com> (raw)
In-Reply-To: <1411743959.3852.45.camel@hornet>
On 9/26/14, 9:05 AM, Pawel Moll wrote:
> To do the correlation you need both timestamps to be "taken"
> simultaneously:
>
> perf event user event
> -----O--------------+-------------O------> t_mono
> : | :
> : V :
> -----O----------------------------O------> t_perf
>
> Of course it's not possible get both values literally at the same time,
> but placing them in a atomic context a couple of instructions from each
> other still gives pretty good results. The larger this distance is, the
An early patchset on this topic added the realtime clock as an event and
an ioctl was used to push a sample into the event stream. In that case
you have wall clock and perf-clock samples taken in the same kernel
context and about as close together as you can get.
https://lkml.org/lkml/2011/2/27/158
https://lkml.org/lkml/2011/2/27/159
David
next prev parent reply other threads:[~2014-09-26 19:25 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-23 17:03 [PATCH v2 0/2] perf: User/kernel time correlation and event generation Pawel Moll
2014-09-23 17:03 ` [PATCH v2 1/2] perf: Add sampling of the raw monotonic clock Pawel Moll
[not found] ` <1411491787-25938-2-git-send-email-pawel.moll-5wv7dgnIgG8@public.gmane.org>
2014-09-24 5:41 ` Namhyung Kim
2014-09-24 5:41 ` Namhyung Kim
[not found] ` <87sijhk21x.fsf-vfBCOVm4yAnB69T4xOojN9BPR1lH4CV8@public.gmane.org>
2014-09-25 10:49 ` Pawel Moll
2014-09-25 10:49 ` Pawel Moll
2014-09-26 6:16 ` Namhyung Kim
2014-09-26 6:16 ` Namhyung Kim
[not found] ` <8738bekith.fsf-vfBCOVm4yAnB69T4xOojN9BPR1lH4CV8@public.gmane.org>
2014-09-26 10:58 ` Pawel Moll
2014-09-26 10:58 ` Pawel Moll
2014-09-26 14:38 ` Namhyung Kim
2014-09-26 15:05 ` Pawel Moll
2014-09-26 19:25 ` David Ahern [this message]
2014-09-26 19:25 ` David Ahern
2014-09-29 14:47 ` Pawel Moll
2014-09-23 17:03 ` [PATCH v2 2/2] perf: Userspace event Pawel Moll
[not found] ` <1411491787-25938-3-git-send-email-pawel.moll-5wv7dgnIgG8@public.gmane.org>
2014-09-24 6:07 ` Namhyung Kim
2014-09-24 6:07 ` Namhyung Kim
[not found] ` <87oau5k0u9.fsf-vfBCOVm4yAnB69T4xOojN9BPR1lH4CV8@public.gmane.org>
2014-09-24 7:20 ` Ingo Molnar
2014-09-24 7:20 ` Ingo Molnar
[not found] ` <20140924072017.GC990-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-09-26 6:21 ` Namhyung Kim
2014-09-26 6:21 ` Namhyung Kim
2014-09-26 10:59 ` Pawel Moll
2014-09-26 11:24 ` Ingo Molnar
2014-09-26 11:24 ` Ingo Molnar
2014-09-25 12:45 ` Pawel Moll
2014-09-26 6:23 ` Namhyung Kim
2014-09-26 6:23 ` Namhyung Kim
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