From: Mikael Pettersson <mikpe@csd.uu.se>
To: john stultz <johnstul@us.ibm.com>
Cc: Chris Friesen <cfriesen@nortelnetworks.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: high res timestamps and SMP
Date: Thu, 20 Nov 2003 11:21:08 +0100 [thread overview]
Message-ID: <16316.38292.729957.491201@alkaid.it.uu.se> (raw)
In-Reply-To: <1069297341.23568.130.camel@cog.beaverton.ibm.com>
john stultz writes:
> On Wed, 2003-11-19 at 14:40, Chris Friesen wrote:
> > We have a requirement to have high-res timestamps available on SMP systems.
...
> o PPC has a nice in-cpu time-base register (ppc folks, feel free to
> smack or correct me on this) which is driven off the bus-clock and is
> synced in hardware.
Last time I checked, all 32-bit PowerPC chips ran that clock at 1/4
of the bus clock speed.
That may be adequate for time-of-day and I/O delays and such, but
it's worthless for timestamps or performance measurements.
It's possible to count core clocks via a performance counter, but
I don't know if they are synced between CPUs.
next prev parent reply other threads:[~2003-11-20 10:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-19 22:40 Chris Friesen
2003-11-20 3:02 ` john stultz
2003-11-20 10:21 ` Mikael Pettersson [this message]
2003-11-20 19:46 ` Anton Blanchard
2003-11-20 22:31 ` Chris Friesen
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