Date: Sun, 02 Nov 2008 17:26:53 -0500 From: "Alexandre \"Sunny\" Kovalenko" <gaijin.k@gmail.com> To: Alexander Motin <mav@FreeBSD.org> Cc: FreeBSD acpi <freebsd-acpi@freebsd.org>, freebsd-mobile@FreeBSD.org Subject: Re: Is the C3 possible with SMP? Message-ID: <1225664813.1202.5.camel@RabbitsDen> In-Reply-To: <490E245C.7070900@FreeBSD.org> References: <490DF584.5080506@FreeBSD.org> <1225656933.1202.2.camel@RabbitsDen> <490E245C.7070900@FreeBSD.org>
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On Mon, 2008-11-03 at 00:06 +0200, Alexander Motin wrote: > Alexandre "Sunny" Kovalenko wrote: > >> I have tried to enable C3 state on my Core2Duo laptop and found that it > >> is not working good. System HZ timer stops during CPU sleep. After some > >> investigation I have found that it is due to LAPIC timer used for HZ > >> stopped during C3 state (same as during AMD's C1E). > >> > >> So the question is: Is it possible (or planned) to make it work somehow? > >> For example, by using some external timer instead of LAPIC's one? > >> > >> ACPI reports about 20% less idle power consumption with C3 state > >> comparing to C2. It would be interesting to get additional half an hour > >> on battery. > >> > > You can get half way there by adding > > > > dev.cpu.1.cx_lowest=C3 > > > > to /etc/sysctl.conf > > Thanks. > > 1. Looks like it does not kill the timer. > 2. I haven't got any benefit from it in idle state. According to > `acpiconf -i 0` I have about 13 Amps (IMHO more looks like Watts) with > both C2 and this half-to-C3, but only 11 Amps in full C3 (but without > timer). > 3. I have got about 10% benefit (33 Amps against 36) when cpu0 is 100% > busy while cpu1 is idle. > You would not happen to have USB loaded or built into kernel? If you do, you will practically never go into C3. What does sysctl dev.cpu | grep cx_usage say? -- Alexandre "Sunny" Kovalenko (Олександр Коваленко)
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