linux-kernel - Re: [PATCH v3 4/5] clocksource: Enable clocksource

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Message-ID: <alpine.LFD.2.02.1303062215190.22263@ionos>
Date:	Wed, 6 Mar 2013 22:15:52 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
cc:	Feng Tang <feng.tang@...el.com>,
	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...e.hu>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	x86@...nel.org, Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-kernel@...r.kernel.org, gong.chen@...ux.intel.com
Subject: Re: [PATCH v3 4/5] clocksource: Enable clocksource_cyc2ns() to cover
 big cycles

On Wed, 6 Mar 2013, H. Peter Anvin wrote:

> On 03/06/2013 06:09 AM, Thomas Gleixner wrote:
> > 
> > This breaks everything which does not have a 64/32bit divide
> > instruction. And you can't replace it with do_div() as that would
> > impose massive overhead on those architectures in the fast path.
> > 
> 
> Could we do the same kind of scaling-by-multiplication that we do in
> kernel/time.c for this?

Not sure what you are referring to. kernel/time.c contains a lot of stuff :)

Thanks,

	tglx
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