Messages in this thread | | | Date | Tue, 27 Dec 2005 00:27:12 +0100 | From | Pavel Machek <> | Subject | Re: [PATCH] i386 No Idle HZ aka dynticks 051221 |
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On Po 26-12-05 17:52:48, Theodore Ts'o wrote: > On Mon, Dec 26, 2005 at 09:38:06PM +0100, Pavel Machek wrote: > > Stupid IBM. I've seen it appearing/disappearing, but did not work out > > when. > > > > No-C4-on-AC is bad -- if you just disconnect AC and walk away, you are > > running without benefits of C4. Bad. Changing benchmarks depending on > > you booting on AC or battery also look nasty. > > The moment you disconnect AC, it C4 automagically appears. When you > reconnect to the AC mains, the C4 state disappears again, at least > from the listing displayed by /proc/acpi/processor/CPU0/power. So the > first issue you brought up isn't a problem.
It does not seem to work like that here. I'm not sure what the exact rules are, but I know that I sometimes have C4 and sometimes not. I have C4 now, and it is used, even when I'm on AC power. Thinkpad X32.
> More of an issue is that there are times when the laptop might think > that it's running of the AC mains, but in fact the owner may have > connected an external battery, and might _want_ the system to be as > frugal as possible with the power.
Yes... OTOH it is not that bad -- we could simply hardcode data from acpi BIOS into kernel, ignore what ACPI says, and drive C4 even on AC power. But that would be hack (tm).
> Whether I boot from AC power battery seems to be immaterial; what > seems to matter is whether or not the laptop is running on battery at > the moment that /proc/acpi/processor/CPU0/power is sampled.
I did not realize ACPI was _that_ clever. Anyway, it is different on my machine... Pavel -- Thanks, Sharp! - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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