Messages in this thread | | | Date | Tue, 21 Aug 2012 12:39:51 +0100 | From | Matthew Garrett <> | Subject | Re: [discussion]sched: a rough proposal to enable power saving in scheduler |
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On Tue, Aug 21, 2012 at 11:42:04AM +0200, Ingo Molnar wrote: > * Matthew Garrett <mjg59@srcf.ucam.org> wrote: > > [...] Putting this kind of policy in the kernel is an awful > > idea. [...] > > A modern kernel better know what state the system is in: on > battery or on AC power.
That's a fundamentally uninteresting thing for the kernel to know about. AC/battery is just not an important power management policy input when compared to various other things.
> > [...] It should never be altering policy itself, [...] > > The kernel/scheduler simply offers sensible defaults where it > can. User-space can augment/modify/override that in any which > way it wishes to. > > This stuff has not been properly sorted out in the last 10+ > years since we have battery driven devices, so we might as well > start with the kernel offering sane default behavior where it > can ...
Userspace has been doing a perfectly reasonable job of determining policy here.
> > [...] because it'll get it wrong and people will file bugs > > complaining that it got it wrong and the biggest case where > > you *need* to be able to handle switching between performance > > and power optimisations (your rack management unit just told > > you that you're going to have to drop power consumption by > > 20W) is one where the kernel doesn't have all the information > > it needs to do this. So why bother at all? > > The point is to have a working default mechanism.
Your suggestions aren't a working default mechanism.
-- Matthew Garrett | mjg59@srcf.ucam.org
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