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From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: John Stultz <john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
	Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>,
	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>,
	Masami Hiramatsu
	<masami.hiramatsu.pt-FCd8Q96Dh0JBDgjK7y7TUQ@public.gmane.org>,
	Christopher Covington
	<cov-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>,
	Namhyung Kim <namhyung-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	David Ahern <dsahern-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
	Tomeu Vizoso <tomeu-XCtybt49RKsYaV1qd6yewg@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Pawel Moll <mail-g3xvULXeDMYS+FvcfC7Uqw@public.gmane.org>
Subject: Re: [PATCH v3 0/3] perf: User/kernel time correlation and event generation
Date: Tue, 04 Nov 2014 09:01:31 +0100	[thread overview]
Message-ID: <3430954.VNaFmamXmP@wuerfel> (raw)
In-Reply-To: <CALAqxLXfy5P0kg-W7hL+Jf1iYv758+-2cTdZwsY8kAns1nvEmg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Monday 03 November 2014 17:11:53 John Stultz wrote:
> I've got some thoughts on what a possible interface that wouldn't be
> awful could look like, but I'm still hesitant because I don't really
> know if exposing this sort of data is actually a good idea long term.
 
I was also thinking (while working on an unrelated patch) we could use
a system call like

int clock_getoffset(clockid_t clkid, struct timespec *offs);

that returns the current offset between CLOCK_REALTIME and the
requested timebase. It is of course racy, but so is every use
of CLOCK_REALTIME. We could also use a reference other than
CLOCK_REALTIME that might be more stable, but passing two arbitrary
clocks as input would make this much more complex to implement.

	Arnd

  parent reply	other threads:[~2014-11-04  8:01 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-04  0:28 [PATCH v3 0/3] perf: User/kernel time correlation and event generation Pawel Moll
2014-11-04  0:28 ` [PATCH v3 2/3] perf: Userspace event Pawel Moll
2014-11-04  6:33   ` Namhyung Kim
     [not found]     ` <87ppd35vbk.fsf-vfBCOVm4yAnB69T4xOojN9BPR1lH4CV8@public.gmane.org>
2014-11-04 16:42       ` Pawel Moll
     [not found]         ` <1415119331.24819.19.camel-5wv7dgnIgG8@public.gmane.org>
2014-11-04 18:40           ` Peter Zijlstra
     [not found]             ` <20141104184031.GM10501-IIpfhp3q70z/8w/KjCw3T+5/BudmfyzbbVWyRVo5IupeoWH0uzbU5w@public.gmane.org>
2014-11-05  6:36               ` Namhyung Kim
     [not found] ` <1415060918-19954-1-git-send-email-pawel.moll-5wv7dgnIgG8@public.gmane.org>
2014-11-04  0:28   ` [PATCH v3 1/3] perf: Use monotonic clock as a source for timestamps Pawel Moll
     [not found]     ` <1415060918-19954-2-git-send-email-pawel.moll-5wv7dgnIgG8@public.gmane.org>
2014-11-04  7:23       ` Peter Zijlstra
     [not found]         ` <20141104072308.GE10501-IIpfhp3q70z/8w/KjCw3T+5/BudmfyzbbVWyRVo5IupeoWH0uzbU5w@public.gmane.org>
2014-11-04 15:25           ` Pawel Moll
     [not found]             ` <1415114727.24819.8.camel-5wv7dgnIgG8@public.gmane.org>
2014-11-04 15:30               ` Peter Zijlstra
2014-11-04  0:28   ` [PATCH v3 3/3] perf: Sample additional clock value Pawel Moll
2014-11-04  0:58   ` [PATCH v3 0/3] perf: User/kernel time correlation and event generation Andy Lutomirski
     [not found]     ` <CALCETrXGoevmD_avz5sQfbbD624vpLW5=-8ovzTPT_5wzNFnVA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-11-04  1:11       ` John Stultz
     [not found]         ` <CALAqxLXfy5P0kg-W7hL+Jf1iYv758+-2cTdZwsY8kAns1nvEmg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-11-04  1:25           ` Andy Lutomirski
     [not found]             ` <CALCETrUAkXKyXzZy4xaYcW2f65Lh=APrU4cFU1zm-qmc6EwB8g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-11-04 15:07               ` Pawel Moll
2014-11-04  8:01           ` Arnd Bergmann [this message]
2014-11-04  8:27             ` Richard Cochran
     [not found]               ` <20141104082728.GB4253-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2014-11-04 10:49                 ` Thomas Gleixner
2014-11-04 16:11                   ` Arnd Bergmann
2014-11-04 16:04             ` John Stultz
2014-11-04  8:24           ` Richard Cochran
2014-11-04  9:24 ` Masami Hiramatsu
     [not found]   ` <54589B58.7080102-FCd8Q96Dh0JBDgjK7y7TUQ@public.gmane.org>
2014-11-04 15:51     ` Pawel Moll
     [not found]       ` <1415116269.24819.14.camel-5wv7dgnIgG8@public.gmane.org>
2014-11-05  8:06         ` Masami Hiramatsu

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