Messages in this thread | | | From | "Doug Smythies" <> | Subject | RE: [RFC/RFT][PATCH v2] cpuidle: New timer events oriented governor for tickless systems | Date | Fri, 2 Nov 2018 08:39:42 -0700 |
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On 2018.10.26 02:12 Rafael J. Wysocki wrote:
...[snip]...
> The v2 is a re-write of major parts of the original patch. > > The approach the same in general, but the details have changed significantly > with respect to the previous version. In particular: > * The decay of the idle state metrics is implemented differently. > * There is a more "clever" pattern detection (sort of along the lines > of what the menu does, but simplified quite a bit and trying to avoid > including timer wakeups). > * The "promotion" from the "polling" state is gone. > * The "safety net" wakeups are treated as the CPU might have been idle > until the closest timer.
...[snip]...
I have been testing this V2 against a baseline that includes all of the pending menu patches. My baseline kernel is somewhere after 4.19, at 345671e.
A side note: Recall that with the menu patch set tests, I found that the baseline reference performance for the pipe test on one core had changed significantly (worse - Kernel 4.19-rc1). Well, now it has changed significantly again (better, and even significantly better than it was for 4.18). 4.18 ~4.8 uSec/loop; 4.19 ~5.2 uSec/loop; 4.19+ (345671e) 4.2 uSec/loop.
This V2 is pretty good. All of the tests that I run gave similar performance and power use between the baseline reference and V2. I couldn't find any issues with the decay stuff, and I tried. (sorry, I didn't do pretty graphs.)
After reading Giovanni's reply the other day, I tried the Phoronix dbench test: 12 clients resulted in similar performance, But TEOv2 used a little less processor package power; 256 clients had about -7% performance using TEOv2, but (my numbers are not exact) also used less processor package power.
On 2018.10.31 11:36 Giovanni Gherdovich wrote:
> Something I'd like to do now is verify that "teo"'s predictions > are better than "menu"'s; I'll probably use systemtap to make > some histograms of idle times versus what idle state was chosen > -- that'd be enough to compare the two.
I don't know what a "systemtap" is, but I have (crude) tools to post process trace data into histograms data. I did 5 minute traces during the 12 client Phoronix dbench test and plotted the results, [1]. Sometimes, to the right of the autoscaled graph is another with fixed scaling. Better grouping of idle durations with TEOv2 are clearly visible.
... Doug
[1] http://fast.smythies.com/linux-pm/k419p/histo_compare.htm
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