Messages in this thread | | | Date | Thu, 17 Mar 2016 09:40:46 +0000 | From | Juri Lelli <> | Subject | Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable |
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On 16/03/16 10:55, Steve Muckle wrote: > On 03/16/2016 03:02 AM, Juri Lelli wrote: > > Hi, > > > > On 16/03/16 09:05, Peter Zijlstra wrote: > >> On Tue, Mar 15, 2016 at 08:36:57PM -0700, Steve Muckle wrote: > >>>> Then again, maybe this knob will be part of the mythical > >>>> power-vs-performance slider? > >>> > >>> Patrick Bellasi's schedtune series [0] (which I think is the referenced > >>> mythical slider) aims to provide a more sophisticated interface for > >>> tuning scheduler-driven frequency selection. In addition to a global > >>> boost value it includes a cgroup controller as well for per-task tuning. > >>> > >>> I would definitely expect the margin/boost value to be modified at > >>> runtime, for example if the battery is running low, or the user wants > >>> 100% performance for a while, or the userspace framework wants to > >>> temporarily tailor the performance level for a particular set of tasks, etc. > >> > >> OK, so how about we start with it as a debug knob, and once we have > >> experience and feel like it is indeed a useful runtime knob, we upgrade > >> it to ABI. > >> > > > > I tend to agree here. To me the margin is something that we need to make > > this thing work and to get acceptable performance out of the box. So we > > can play with it while debugging, but I consider the schedtune slider as > > the way to tune the system at runtime. > > Could the default schedtune value not serve as the out of the box margin? >
I'm not sure I understand you here. For me schedtune should be disabled by default, so I'd say that it doesn't introduce any additional margin by default. But we still need a margin to make the governor work without schedtune in the mix.
> Regardless I agree that a debug interface is the way to go for now while > we figure things out. >
Looks good to me.
Best,
- Juri
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