Date: Sat, 12 Nov 2005 21:44:28 +0100
From: Vojtech Pavlik <vojtech@suse.cz>
To: Andi Kleen <ak@suse.de>
Cc: Jan Beulich <JBeulich@novell.com>, linux-kernel@vger.kernel.org,
       discuss@x86-64.org
Subject: Re: [PATCH 13/39] NLKD/x86-64 - time adjustment
Message-ID: <20051112204428.GA14733@midnight.suse.cz>
References: <43720DAE.76F0.0078.0@novell.com> <200511110312.15616.ak@suse.de> <20051112092200.GA7997@midnight.suse.cz> <200511121821.11552.ak@suse.de>
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On Sat, Nov 12, 2005 at 06:21:11PM +0100, Andi Kleen wrote:
> On Saturday 12 November 2005 10:22, Vojtech Pavlik wrote:
> 
> > Is there any advantage to using 64-bit HPET? 
> 
> Yes - it can tolerate long delays between ticks, e.g. caused by noidletick / 
> debuggers / target probes / smm etc. At least the first case will be fairly
> important soon.

A 32-bit 14 MHz HPET counter will overflow in approximately 5 minutes. I
don't think going 64-bit makes sense for noidletick, but for debuggers,
etc, it could make a good sense indeed.

> > It's read is even slower 
> 
> Why? The read should be on cache line granuality and there shouldn't
> be any difference in theory.
 
I'll try to measure this. Indeed, in theory there shouldn't be a
significant difference.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR
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