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Date: Thu, 29 Jan 2009 14:54:47 -0500 From: Dave Jones <davej@...hat.com> To: Xiaoning Ding <dingxn@...il.com> Cc: Michael Tokarev <mjt@....msk.ru>, linux-kernel@...r.kernel.org Subject: Re: a question about p4_clockmod module on Xeon quad core processors On Thu, Jan 29, 2009 at 11:40:25AM -0800, Xiaoning Ding wrote: > Thanks for the explanation. So the conclusion is that ACPI-cpufreq > can reduce power consumption by lowering cpu frequencies, and > p4-clockmod can hardly save power because CPU frequences are not > changed. yes. and also that it inhibits entering deeper C states for longer periods. > My experiments do not consider power consumption. It only requires to > slow down the speed of some cores by either reducing frequencies or > clock modulation. In such case, p4-clockmod is still a good choice for > me. Can anyone give me some hints on whether p4-clockmod works on Xeon > quad-core processors, and how to get it work? I'm not sure if the registers are still there on quad cores, but I would be surprised if they weren't. Hitting them directly with msr tools is probably the best way, or writing a small program that manipulates /dev/cpu/*/msr directly. Dave -- http://www.codemonkey.org.uk -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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