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

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Message-ID: <5137AF96.6050003@linux.intel.com>
Date:	Wed, 06 Mar 2013 13:05:26 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
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 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?

	-hpa


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