linux-kernel - Re: [RFC/RFT][PATCH v2] cpuidle: New timer events oriented governor for tickless systems

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5001963.Ahc0lEbC1L@aspire.rjw.lan>
Date:   Sun, 04 Nov 2018 11:06:17 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Doug Smythies <dsmythies@...us.net>
Cc:     'Giovanni Gherdovich' <ggherdovich@...e.cz>,
        'Srinivas Pandruvada' <srinivas.pandruvada@...ux.intel.com>,
        'Peter Zijlstra' <peterz@...radead.org>,
        'LKML' <linux-kernel@...r.kernel.org>,
        'Frederic Weisbecker' <frederic@...nel.org>,
        'Mel Gorman' <mgorman@...e.de>,
        'Daniel Lezcano' <daniel.lezcano@...aro.org>,
        'Linux PM' <linux-pm@...r.kernel.org>
Subject: Re: [RFC/RFT][PATCH v2] cpuidle: New timer events oriented governor for tickless systems

On Friday, November 2, 2018 4:39:42 PM CET Doug Smythies wrote:
> On 2018.10.26 02:12 Rafael J. Wysocki wrote:
> 
> ...[snip]...

Again, thanks a lot for the feedback, it is appreciated very much!

> > 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.

That's awesome!

> 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.

Good to know, thank you!

> 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

Thanks for the graphs.  At least they show the consistent underestimation of
the idle duration in menu if I'm not mistaken.

Cheers,
Rafael