From: Holger Macht <hmacht@suse.de>
To: "Brown, Len" <len.brown@intel.com>
Cc: thoenig@suse.de, linux-acpi@vger.kernel.org,
linux-laptop@vger.kernel.org, Andi Kleen <ak@suse.de>
Subject: Re: kernel vs user power management
Date: Wed, 17 May 2006 19:41:24 +0200 [thread overview]
Message-ID: <20060517174123.GA7092@linux-ersb> (raw)
In-Reply-To: <CFF307C98FEABE47A452B27C06B85BB679BACB@hdsmsx411.amr.corp.intel.com>
On Wed 17. May - 11:41:16, Brown, Len wrote:
>
> >> I installed SL10.1 today on a P3M laptop (Dell D600)
> >> and it defaults to the "Powersave" scheme which includes
> >> "Dynamic Frequency Scaling" (ondemand), so that is good.
> >>
> >> However, by defaulit "Allow Throttling" is CHECKED
> >> and Max % is set to 50%.
> >>
> >> Exactly what does this mean?
> >> I looked in /proc/acpi/processor/*/throttling and the
> >> laptop is still in T0.
> >
> >It means that the powersaved throttles your CPU if there is no load and
> >dethrottles if there is load. It's that way already for
> >several years and
> >I only got a report about performance loss on SMP systems, so
> >we don't do
> >throttling by default on those systems.
>
> I see -- my test platform changed from dual-core to single-core,
> so I didn't see this issue before.
>
> >> Is there an easy way for me to modify the kernel to
> >> convince the powersaved application that the system
> >> does not support throttling? I'm thinking that we've
> >> given user-space too much rope and it has proceeded
> >> to hang itself.
> >
> >I'm currently working on a solution to allow throttling only on systems
> >which don't support CPUfreq. At the point this thread came up, or a few
> >days later as we talked about it, I completely agreed with you. But at
> >that time we already had RC1 in regard to SUSE Linux 10.1, so
> >there was no
> >possibility anymore to change such a default behaviour. For
> >the unstable
> >powersave realeases, there will come up some changes soon, though.
>
> I understand, though I think it would be more practical to not
> enable throttling by default on any system; and for systems
> with cpufreq to not even advertise this option to users.
Agreed. We kept this already far too long without seeing a real gain.
>
> Also, I think something is broken today.
> If I use the GUI to disable throttling in the Powersave scheme
> and save, and then pull out the plug; a window with "watch
> .../throttling"
> shows that the system drops into T2, and then bounces back to T0.
I really don't see a possibility that powersaved could be the culprit in
this case. If it's disabled in /etc/powersave/scheme_powersave, well it
surely doesn't touch this file:
bool ThrottleInterface::throttle(int percent)
{
if (!_throttling_supported
|| !config_obj->current_scheme->ALLOW_THROTTLING) {
return false;
}
...
}
>
> I don't trust the application to keep its hands off this file,
> so I think that I need a way to disable/remove that file.
If you can reproduce that it switches to T2 when you do a rcpowersaved
restart or on every unplug, it would actually be a bug which is worth
to be reported.
Regards,
Holger
next prev parent reply other threads:[~2006-05-17 17:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-17 15:41 kernel vs user power management Brown, Len
2006-05-17 17:41 ` Holger Macht [this message]
-- strict thread matches above, loose matches on Subject: below --
2006-05-17 18:25 Brown, Len
2006-05-17 4:20 Brown, Len
2006-05-17 9:14 ` Holger Macht
2006-04-09 3:06 Brown, Len
2006-04-09 6:07 ` Andi Kleen
2006-04-10 8:35 ` Holger Macht
2006-04-08 6:42 Brown, Len
2006-04-08 17:18 ` Holger Macht
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