From: "Chris Friesen" <cfriesen@nortel.com>
To: markh@compro.net
Cc: Arjan van de Ven <arjan@infradead.org>,
"linux-os (Dick Johnson)" <linux-os@analogic.com>,
Jan Engelhardt <jengelh@medozas.de>,
"Kok, Auke" <auke-jan.h.kok@intel.com>,
"solsTiCe d'Hiver" <solstice.dhiver@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: PROBLEM: no cpu MHz in /proc/cpuinfo on 2.6.25.4-rt6
Date: Wed, 11 Jun 2008 15:39:24 -0600 [thread overview]
Message-ID: <4850460C.5030406@nortel.com> (raw)
In-Reply-To: <48503EB9.6000606@compro.net>
Mark Hounschell wrote:
> If they are not the same how do you know at what rate the tsc is counting.
You don't, at least not easily. The timekeeping subsystem knows, but it
might be unstable, or change with cpu frequency or cpu going idle, etc.
> But back to "how usable is rdtsc for time", is there a
>
> clock_gettime(CLOCK_MONOTONIC, &time) equivalent that can be used in the kernel?
With current kernels it looks like ktime_get_ts() should give exactly
the same results, since it's how that userspace function is implemented.
With a stable tsc it seems like it should give full accuracy.
Chris
next prev parent reply other threads:[~2008-06-11 21:40 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-10 19:52 PROBLEM: no cpu MHz in /proc/cpuinfo on 2.6.25.4-rt6 solsTiCe d'Hiver
2008-06-10 20:13 ` Arjan van de Ven
2008-06-10 20:42 ` Kok, Auke
2008-06-11 12:42 ` Jan Engelhardt
2008-06-11 13:36 ` Arjan van de Ven
2008-06-11 13:52 ` Jan Engelhardt
2008-06-11 13:58 ` Arjan van de Ven
2008-06-11 14:14 ` linux-os (Dick Johnson)
2008-06-11 15:10 ` Peter Zijlstra
2008-06-11 15:36 ` Arjan van de Ven
2008-06-11 16:59 ` Mark Hounschell
2008-06-11 17:44 ` Arjan van de Ven
2008-06-11 17:54 ` Mark Hounschell
2008-06-11 20:29 ` Arjan van de Ven
2008-06-11 20:37 ` Mark Hounschell
2008-06-11 20:55 ` Arjan van de Ven
2008-06-11 20:59 ` Mark Hounschell
2008-06-11 20:58 ` Arjan van de Ven
2008-06-11 21:08 ` Mark Hounschell
2008-06-11 21:28 ` Arjan van de Ven
2008-06-11 21:39 ` Chris Friesen [this message]
2008-06-11 23:08 ` Andi Kleen
2008-06-11 16:08 ` Ray Lee
2008-06-11 16:32 ` Arjan van de Ven
2008-06-11 12:40 ` Jan Engelhardt
2008-06-11 14:15 ` solsTiCe d'Hiver
2008-06-11 14:36 ` Jan Engelhardt
2008-06-11 15:35 ` solsTiCe d'Hiver
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