Mark.Haywood wrote: > Li, Aubrey wrote: >> Mark.Haywood wrote: >> >> >>> Li, Aubrey wrote: >>> >>>> Firstly, many thanks to report this bug, :-) >>>> >>>> Before we setup powertop bug track system on >>>> defect.opensolaris.org, can we report bug to the mailing list >>>> first? >>>> >>>> my comments about this bug: >>>> >>>> This is a very good raise-up, really. But I think it'd better to >>>> place this bug into Todo list. Currently kernel doesn't support any >>>> mechanism to obtain the frequency in the "turbo mode". So, powertop >>>> can't report any related info. Actually hardware feedback machanism >>>> exists on the processor, We need to enable it. >>>> >>>> >>> It is true that the APERF/MPERF hardware feedback mechanism >>> can help to >>> identify that a processor has been in "turbo mode". But unless I'm >>> mistaken there is no guarantee that when the processor is in Turbo >>> Mode that APERF/MPERF will catch it. Among other things, it would >>> depend upon your polling interval - which currently is pretty long. >>> >> >> Can't we assume the processor is in turbo mode when we are in >> P0 = (market frequency) + 1Mhz? >> > > I don't think that the processor being at P0 guarantees that it is in > turbo mode. It means that the processor should operate no lower than > market frequency and if the circumstances present themselves, then the > hardware might overclock the processor for some amount of time. > When kernel boot, we know wether the platform support turbo mode or not. I happened to have a box support turbo mode.
when turbo mode is enabled, supported frequency is 800Mhz:1600Mhz:2400Mhz:2401Mhz, and when turbo mode is disabled, supported frequency is 800Mhz:1600Mhz:2400Mhz. So, in turbo mode should be 1). turbo mode is supported 2). processor is in P0 3). P0 > marked frequency. >> >>> What exactly would powertop report about 'turbo mode'? Amount of >>> time spent in "turbo mode"? I think a metric like that is bound to >>> be incorrect given the current hardware support isn't it? >>> >> >> If I understand correctly, the bug reporter want to know the average >> frequency in turbo mode(P0) in a sampling period, if hardware >> support it. >> > > This doesn't make much sense to me. A processor is likely (though > maybe not with the current Solaris implementation), to switch in and > out of P0 > many times during a (powertop defined?) polling period. > It's doable I think. we can calculate the APERF difference and MPERF difference between in and out P0. then we will have a ratio by the two difference. so we can know the average frequency. Thanks, -Aubrey
