From: george anzinger <george@mvista.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Fionn Behrens <fionn@unix-ag.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Grover, Andrew" <andrew.grover@intel.com>
Subject: Re: System time warping around real time problem - please help
Date: Wed, 26 Mar 2003 08:12:51 -0800 [thread overview]
Message-ID: <3E81D183.6040708@mvista.com> (raw)
In-Reply-To: <1048689492.31839.13.camel@irongate.swansea.linux.org.uk>
Alan Cox wrote:
> On Wed, 2003-03-26 at 02:28, george anzinger wrote:
>
>>Stands for Time Stamp Counter. It is a special cpu register that
>>basically counts cpu cycles. Some times (incorrectly me thinks) it is
>>affected by power management code which slows the cpu by changing the
>>cpu frequency.
>
>
> Not incorrectly. It counts cpu clocks, its designed for profiling and
> the like. There is no guarantee in any Intel MP standard that the clocks
> are synched up.
>
I seem to recall a different notion of correctness from Andy Grover...
but memory may deceive :(
As for sync, I would think it is a mother board issue.
But as you say, Intel should put in a usable counter. The HPET seems
like it has the capabilities, however, I suspect that it is a slow
read. Any idea how many cycles it takes to do a memory mapped I/O access?
--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
next prev parent reply other threads:[~2003-03-26 16:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-25 16:32 System time warping around real time problem - please help Fionn Behrens
2003-03-25 17:07 ` Richard B. Johnson
2003-03-25 17:17 ` Tim Schmielau
2003-03-25 18:12 ` Fionn Behrens
2003-03-25 18:29 ` Richard B. Johnson
2003-03-25 21:16 ` Fionn Behrens
2003-03-25 22:14 ` george anzinger
2003-03-25 22:55 ` Fionn Behrens
2003-03-26 0:13 ` Alan Cox
2003-03-26 2:28 ` george anzinger
2003-03-26 14:38 ` Alan Cox
2003-03-26 16:12 ` george anzinger [this message]
2003-03-26 17:06 ` Richard B. Johnson
2003-03-26 18:12 ` george anzinger
2003-03-26 3:11 ` Chris Friesen
2003-03-26 14:35 ` Alan Cox
2003-03-26 10:48 ` Fionn Behrens
[not found] <20030325164014$031c@gated-at.bofh.it>
2003-03-26 9:31 ` Kay Diederichs
-- strict thread matches above, loose matches on Subject: below --
2003-04-03 13:22 Fionn Behrens
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