On Tue, 2016-08-23 at 11:48 +0800, Wanpeng Li wrote: > Hi Rafael, > 2016-08-01 7:38 GMT+08:00 Rafael J. Wysocki <[email protected]>: > > > > From: Rafael J. Wysocki <[email protected]> > > > > The PID-base P-state selection algorithm used by intel_pstate for > > Core processors is based on very weak foundations. Namely, its > > decisions are mostly based on the values of the APERF and MPERF > > feedback registers and it only estimates the actual utilization to > > check if it is not extremely low (in order to avoid getting stuck > > in the highest P-state in that case). > > > > Since it generally causes the CPU P-state to ramp up quickly, it > > leads to satisfactory performance, but the metric used by it is > > only > > really valid when the CPU changes P-states by itself (ie. in the > > turbo > > range) and if the P-state value set by the driver is treated by the > > CPU as the upper limit on turbo P-states selected by it. > > Do you mean CPU will ignore the request value which is submitted by > intel_pstate driver in the turbo range, but respect the upper limit > on > the turbo P-states which is submitted by intel_pstate driver? Any request to request a P-state even upper limit can be totally ignored in turbo range.
Thanks, Srinivas > > Regards, > Wanpeng Li > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" > in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html
