From: Josh Triplett <josh@joshtriplett.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@infradead.org>,
john stultz <johnstul@us.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
lkml <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@tglx.de>, Ingo Molnar <mingo@elte.hu>,
Andi Kleen <ak@suse.de>,
nikolag@ca.ibm.com, Darren Hart <dvhltc@us.ibm.com>
Subject: Re: [RFC][PATCH] Introduce CLOCK_REALTIME_COARSE
Date: Wed, 22 Jul 2009 14:39:46 -0700 [thread overview]
Message-ID: <20090722213942.GA4337@josh-work.beaverton.ibm.com> (raw)
In-Reply-To: <1248097754.15751.8867.camel@twins>
On Mon, Jul 20, 2009 at 03:49:14PM +0200, Peter Zijlstra wrote:
> On Mon, 2009-07-20 at 06:33 -0700, Arjan van de Ven wrote:
> > > Maybe power64, sparc64 and s390x qualify, but certainly nothing on x86
> > > does.
> >
> > the x86 on my desk disagrees.
>
> >From what I know even nehalem doesn't have fully synced tscs when your
> machine is large enough, and the timers are still a tad expensive.
All single-socket Nehalem boards have synced TSCs, and some multi-socket
Nehalem boards have synced TSCs, notably Intel's. I don't know if you
can safely rely on the latter, though.
> Maybe your desktop is next-gen? 't would be nice to finally have an x86
> that has usable clock and timer hardware.
x86 CPUs with the ARAT feature ("always running APIC timer") will let
you use the local APIC even in deep C-states. I don't know about the
overhead of the local APIC.
- Josh Triplett
next prev parent reply other threads:[~2009-07-22 21:40 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-17 23:39 john stultz
2009-07-18 8:30 ` Thomas Gleixner
2009-07-18 22:09 ` john stultz
2009-07-18 22:30 ` Arjan van de Ven
2009-07-20 11:17 ` Peter Zijlstra
2009-07-20 12:22 ` Paul E. McKenney
2009-07-20 13:33 ` Arjan van de Ven
2009-07-20 13:49 ` Peter Zijlstra
2009-07-22 21:39 ` Josh Triplett [this message]
2009-07-21 22:31 ` john stultz
2009-07-22 1:26 ` john stultz
2009-08-01 12:21 ` Andy Lutomirski
2009-07-18 12:09 ` Ingo Molnar
2009-07-18 22:20 ` john stultz
2009-07-19 3:00 ` Chris Snook
2009-07-19 6:14 ` Arjan van de Ven
2009-07-19 6:48 ` Nicholas Miell
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