cpufreqd as standard install?
mjg59 at srcf.ucam.org
Thu Mar 8 17:11:04 UTC 2012
On Thu, Mar 08, 2012 at 11:22:04AM -0500, Phillip Susi wrote:
> On 3/8/2012 11:10 AM, Matthew Garrett wrote:
> >Yes, if those are the actual power figures. But they're typically not
> >going to be.
> Can you be a little less vague and hand wavy?
My i7 draws about 7W when fully loaded at 800MHz, and about 27W when
fully loaded at 2.7GHz. That's a 3.4x performance improvement at a
3.9x power increase. So, naively, that does result in a fixed amount
of work being carried out in a smaller amount of energy, although not
anywhere near the extent that you're describing.
But this is a very strange workload to be optimising for. First, it's
entirely CPU-bound. If it involves IO then you're going to be keeping IO
devices in a higher power state for longer, which wipes out the
advantage. Second, it makes the assumption that the user doesn't care
how much time it takes. That's basically never true.
The only reason not to use race-to-idle is because you have an amazingly
specific workload, one that's CPU bound and not user-interactive. That
discounts pretty much every desktop, mobile and server use case. It's
really not worth worrying about.
Matthew Garrett | mjg59 at srcf.ucam.org
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