Date: Fri, 04 Mar 2005 10:14:21 -0800 From: Nate Lawson <nate@root.org> To: Kevin Oberman <oberman@es.net> Cc: current@FreeBSD.ORG Subject: Re: patch: p4tcc and speedstep cpufreq drivers Message-ID: <4228A57D.9030408@root.org> In-Reply-To: <20050304165502.19EED5D07@ptavv.es.net> References: <20050304165502.19EED5D07@ptavv.es.net>
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Kevin Oberman wrote: >>Date: Thu, 03 Mar 2005 21:37:05 -0800 >>From: Nate Lawson <nate@root.org> >> >>Kevin Oberman wrote: >> >>>OK. This makes me feel a bit better, but I still think I'll leave TCC >>>out of the equation as it makes the various frequency steps vary uneven >>>to the point that lowering dev.cpu.0.freq would increase performance >>>(and the reverse, as well) and it causes my system to hang when >>>throttled back too far. It never hangs with TCC disabled although my >>>lowest "frequency" is now just 150 MHz. >> >>Would you test with hint.acpi_throttle.0.disabled="1" instead of >>disabling p4tcc? I think p4tcc is not the problem, it's the combination >>of the two. I think there are some problems when both the chipset >>(externally) and processor (internally) assert STOPCLOCK. If this works >>for you with no hangs, I'll commit code to disable acpi_throttle when >>p4tcc is present. p4tcc is more efficient than acpi_throttle since the >>latter is done through the chipset, giving more chance for race >>conditions, latency, etc. > > Looks like you are right on the button. p4tcc with throttling disabled > yields the best results I have seen. The performance is just a > little better than the "normalized" value I would expect where > throttling produced performance just a little worse. As long as I don't > run both, I don't hang at any speed and I don't get increased > performance with decreased speed. Ok, I'll commit my patch. > I really want to try some tests while actively monitoring current draw > some day, but it will require hacking on a power brick and I don't have > one I can play with at the moment. That would provide some REAL > indication of power savings with reduced performance and make tuning > more accurate. I have one we made for this purpose. Also fun on refrigerators. -- Nate
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