> P0 is not equal to turbo mode. P0 means the system is requesting to > the speed of the max performance. When Turbo mode is enabled, P0 give > the system a chance to go into turbo mode, but whether the processor > enter > turbo mode or not is determined by the hardware. So, even if APERF/MPERF > may be < 1, if DTrace says we are in P0, we should let PowerTOP and > users > know the system is requesting max performance speed, not max non turbo > speed.
I agree with what you say above, but I am sorry I need more clarification on the display issue. Now say max non-turbo frequency is 2400 and P0 is 2401 as displayed by powertop. PowerTop does not diplay P0, P1 ... etc. It only displays frequencies 2000, 2400, 2401 etc. i.e. the display is something like, P-state Frequency 2000 2400 2401 Now considering your case, let us say IDA is enabled and Dtrace says we are in P0. CURRENTLY powertop display 100% in 2401. However, sampling the APERF/MPERF values, if the ratio <=1 we are running at 2400 MHz (*I agree in P0, but it is 2400 and NOT 2401*). If the ratio is larger than one, then we are running at some frequency higher than 2400Hz. This is precisely what I do. IDA enabled and APERF/MPERF <=1, I display 100% next to 2400Mhz (This means we are in P0 and running at 2400 Mhz). If APERF/MPERF > 1, I display AVERAGE frequency instead of *2401 Mhz* and the *time spent there*. Just because IDA is enabled will it not be incorrect to display 100% next to 2401 just because Dtrace probe tells we are in P0 as powertop does currently ? Thanks, -vinay ----- Original Message ----- From: "Li, Aubrey" <[email protected]> Date: Thursday, August 14, 2008 5:42 pm Subject: RE: [tesla-dev] PowerTop must support Turbo mode: webrev link onopensolaris To: Vinay Devadas <Vinay.Devadas at Sun.COM> Cc: tesla-dev at opensolaris.org > Vinay Devadas wrote: > > >> when IDA is enabled, if DTrace says we are in P0, > >> we really in P0 in terms of OSPM. So not necessary to change p-state > >> index and percent. > >> > > > > Even when IDA is enabled and Dtrace says we are in P0, the > > ratio APERF/MPERF *may be* <=1. This means we were just > > running at max non turbo frequency (marketed as P1) and not > > actually in turbo mode (marketed as P0). Therefore it is > > necessary to change p-state index and percent and do check. Correct > > me if I am wrong. > > > P0 is not equal to turbo mode. P0 means the system is requesting to > the speed of the max performance. When Turbo mode is enabled, P0 give > the system a chance to go into turbo mode, but whether the processor > enter > turbo mode or not is determined by the hardware. So, even if APERF/MPERF > may be < 1, if DTrace says we are in P0, we should let PowerTOP and > users > know the system is requesting max performance speed, not max non turbo > speed. > > Thanks, > -Aubrey
