Date: Fri, 01 Feb 2008 17:37:47 +0200 From: Andriy Gapon <avg@icyb.net.ua> To: Nate Lawson <nate@root.org> Cc: freebsd-acpi@freebsd.org Subject: Re: cx_lowest and CPU usage Message-ID: <47A33CCB.3090902@icyb.net.ua> In-Reply-To: <479F62D9.6080703@root.org> References: <479F0ED4.9030709@icyb.net.ua> <479F62D9.6080703@root.org>
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on 29/01/2008 19:31 Nate Lawson said the following: > Andriy Gapon wrote: >> Report for 7.0-RC1 on quite old hardware: 440BX-based motherboard, >> 450Mhz Pentium III (Katmai). >> >> cx_supported claims to support C1, C2, C3. If I set cx_lowest to C3 it >> immediately gets backed out to C2 with a kernel message about too many >> short sleeps. But that's not a problem. >> There is a weird thing: if I change cx_lowest to C2 when the machine is >> completely idle, top shows that CPU usage for interrupts immediately >> jumps to almost 20%. Change cx_lowest to C1, CPU usage drops back to >> almost 0%. >> Is this normal ? >> If not, does this indicate some problem in idle routine or is this just >> incorrect statistics calculation ? Or maybe something with HW ? > > Leave it at C1. Apparently C2 and C3 don't work on your machine. > That's understandable with older, non-laptop hw. Nate, I understand the advice. I event see that the code has the following comment "Disable C3 support for all PIIX4 chipsets", but apparently it does a little bit different thing. Out of curiosity, what could be wrong with C2 state ? vmstat -i reports identical interrupt rates with both cx_lowest=C1 and cx_lowest=C2, so I wonder where from the extra interrupt CPU utilization comes. -- Andriy Gapon
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