On Fri, Apr 13, 2018 at 06:57:39PM -0700, Francisco Jerez wrote:
> Peter Zijlstra <pet...@infradead.org> writes:
> > On Thu, Apr 12, 2018 at 12:55:39PM -0700, Francisco Jerez wrote:
> >> Actually assuming that a single geometric feature of the power curve is
> >> known -- it being convex in the frequency range allowed by the policy
> >> (which is almost always the case, not only for Intel CPUs), the optimal
> >> frequency for an IO-bound workload is fully independent of the exact
> >> power curve -- It's just the minimum CPU frequency that's able to keep
> >> the bottlenecking IO device at 100% utilization. 
> >
> > I think that is difficult to determine with the information at hand. We
> > have lost all device information by the time we reach the scheduler.
> I assume you mean it's difficult to tell whether the workload is
> CPU-bound or IO-bound?  Yeah, it's non-trivial to determine whether the
> system is bottlenecking on IO, it requires additional infrastructure to
> keep track of IO utilization (that's the purpose of PATCH 1), and even

Note that I've not actually seen any of your patches; I got Cc'ed on

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