From owner-freebsd-acpi@FreeBSD.ORG Thu Feb 14 18:03:06 2008 Return-Path: Delivered-To: freebsd-acpi@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C376A16A46C for ; Thu, 14 Feb 2008 18:03:06 +0000 (UTC) (envelope-from bengta@P142.sics.se) Received: from kloster.sics.se (kloster.sics.se [193.10.65.127]) by mx1.freebsd.org (Postfix) with ESMTP id 354CA13C442 for ; Thu, 14 Feb 2008 18:03:05 +0000 (UTC) (envelope-from bengta@P142.sics.se) Received: from P142.sics.se (h150n1-u-d1.ias.bredband.telia.com [213.64.92.150]) by kloster.sics.se (8.13.7/8.13.7) with ESMTP id m1EHEbu9029892 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 14 Feb 2008 18:14:37 +0100 Received: from P142.sics.se (localhost [127.0.0.1]) by P142.sics.se (8.14.2/8.14.2) with ESMTP id m1EHEapn003772; Thu, 14 Feb 2008 18:14:36 +0100 (CET) (envelope-from bengta@P142.sics.se) Received: (from bengta@localhost) by P142.sics.se (8.14.2/8.14.2/Submit) id m1EHEXCY003771; Thu, 14 Feb 2008 18:14:33 +0100 (CET) (envelope-from bengta@P142.sics.se) To: Andriy Gapon From: Bengt Ahlgren In-Reply-To: <47B4103A.6090902@icyb.net.ua> (Andriy Gapon's message of "Thu\, 14 Feb 2008 11\:56\:10 +0200") User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (berkeley-unix) References: <479F0ED4.9030709@icyb.net.ua> <479F62D9.6080703@root.org> <47A33CCB.3090902@icyb.net.ua> <47B0C10F.6000109@icyb.net.ua> <47B4103A.6090902@icyb.net.ua> Date: Thu, 14 Feb 2008 18:14:33 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: freebsd-acpi@freebsd.org Subject: Re: cx_lowest and CPU usage X-BeenThere: freebsd-acpi@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: ACPI and power management development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 14 Feb 2008 18:03:06 -0000 Andriy Gapon writes: > on 11/02/2008 23:41 Andriy Gapon said the following: >> on 01/02/2008 17:37 Andriy Gapon said the following: >>>> Andriy Gapon wrote: >>>>> Report for 7.0-RC1 on quite old hardware: 440BX-based motherboard, >>>>> 450Mhz Pentium III (Katmai). > [snip] >>>>> 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 ? > [snip] > > I mis-reported the issue. Actually the above behavior occurs if I > throttle CPU 50% (via acpi throttling) and I am not concerned about this > at all. > > C2 has even stranger effects. > On almost idle system, with cx_lowest=C1, top reports about 0-2% user, > 0% nice, 0-2% system, 1-2% interrupt, 94-98% idle. > After changing cx_lowest to C2, I see the following: 0-2% user, 0% nice, > 0-2% system, 94-98% interrupt, 1-2% idle. I see a similar effect on my TP with Pentium-M when it is in C3 or C4, but it's more in the order of 4% when in C3 and some 10-15% in C4. I think that the additional time accounted to interrupts is due to the time it takes to wake the CPU up from the particular Cx-state. My C3 takes 85 (us?? or cycles???): [root@P142 ~]# sysctl dev.cpu.0.cx_supported dev.cpu.0.cx_supported: C1/1 C2/1 C3/85 [...] > Just in case, here's a little bit of sysctl output: > dev.cpu.0.freq: 448 > dev.cpu.0.freq_levels: 448/-1 224/-1 > dev.cpu.0.cx_supported: C1/0 C2/90 > dev.cpu.0.cx_lowest: C2 > dev.cpu.0.cx_usage: 1.71% 98.28% With this slow CPU, a wakeup time of 90 from C2 could very well result in this much interupt time. It just barely manages to wake up, execute the clock interrupt and go to sleep again before the next clock interrupt. What if you reduce HZ? Bengt