* Matthew Garrett <mj...@srcf.ucam.org> wrote:
> On Mon, Aug 20, 2012 at 10:06:06AM +0200, Ingo Molnar wrote:
>
> > If the answer is 'yes' then there's clear cases where the kernel
> > (should) automatically know the events where we switch from
> > balancing for performance to balancing for power:
>
> No. We can't identify all of these cases and we can't identify
> corner cases. [...]
There's no need to identify 'all' of these cases - but if the
kernel knows then it can have intelligent default behavior.
> [...] 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.
> [...] 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 ...
> [...] 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.
Thanks,
Ingo
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