On Thu, May 17, 2018 at 6:42 PM, Srinivas Pandruvada <srinivas.pandruv...@linux.intel.com> wrote: > On Thu, 2018-05-17 at 18:16 +0200, Peter Zijlstra wrote: >> On Thu, May 17, 2018 at 08:41:32AM -0700, Srinivas Pandruvada wrote: >> > One more point to note. Even if we calculate some utilization based >> > on >> > the freq-invariant and arrive at a P-state, we will not be able to >> > control any P-state in turbo region (not even as a cap) on several >> > Intel processors using PERF_CTL MSRs. >> >> Right, but don't we need to set the PERF_CTL to max P in order to >> access the turbo bins? > > Any PERF_CTL setting above what we call "Turbo Activation ratio" (which > can be less than P1 read from platform info MSR) will do that on these > systems (Most clients from Ivy bridge). > >> So we still need to compute a P state, but as soon as we >> reach max P, we're done. > > What will happen if we look at all core turbo as max and cap any > utilization above this to 1024?
I was going to suggest that. Otherwise, if we ever get (say) the max one-core turbo at any point and the system only runs parallel workloads after that, it will appear as underutilized.
