Date: Thu, 14 Feb 2008 12:05:36 -0800 From: "Kevin Oberman" <oberman@es.net> To: Bengt Ahlgren <bengta@sics.se> Cc: freebsd-acpi@freebsd.org, Andriy Gapon <avg@icyb.net.ua> Subject: Re: cx_lowest and CPU usage Message-ID: <20080214200536.49E214500F@ptavv.es.net> In-Reply-To: Your message of "Thu, 14 Feb 2008 18:14:33 %2B0100." <uh7bq6jcveu.fsf@P142.sics.se>
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--==_Exmh_1203019536_1097P Content-Type: text/plain; charset=us-ascii Content-Disposition: inline > From: Bengt Ahlgren <bengta@sics.se> > Date: Thu, 14 Feb 2008 18:14:33 +0100 > Sender: owner-freebsd-acpi@freebsd.org > > Andriy Gapon <avg@icyb.net.ua> 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? Possible dumb question. Do you (either of you) have USB drivers in your kernel or loaded? This is just a shot in the dark, but I have seen weird things when I have USB drivers loaded and usually don't load them on my laptop until/unless I need them. At very least, USB kills the battery on my T43 a LOT faster. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751 --==_Exmh_1203019536_1097P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (FreeBSD) Comment: Exmh version 2.5 06/03/2002 iD8DBQFHtJ8Qkn3rs5h7N1ERAvGRAJwInpGtXrlDaCFH5G0TrV5/K+n0lwCghE4y tY4SrRrS8j2G49pfgzgxN1A= =M9n6 -----END PGP SIGNATURE----- --==_Exmh_1203019536_1097P--
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