Messages in this thread | | | From | Vincent Guittot <> | Date | Tue, 29 Oct 2019 13:54:24 +0100 | Subject | Re: [PATCH v2] sched: rt: Make RT capacity aware |
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On Tue, 29 Oct 2019 at 13:46, Qais Yousef <qais.yousef@arm.com> wrote: > > On 10/29/19 13:20, Vincent Guittot wrote: > > > > Making big cores the default CPUs for all RT tasks is not a minor > > > > change and IMO locality should stay the default behavior when there is > > > > no uclamp constraint > > > > > > How this is affecting locality? The task will always go to the big core, so it > > > should be local. > > > > local with the waker > > You will force rt task to run on big cluster although waker, data and > > interrupts can be on little one. > > So making big core as default is far from always being the best choice > > This is loaded with assumptions IMO. AFAICT we don't know what's the best > choice. > > First, the value of uclamp.min is outside of the scope of this patch. Unless > what you're saying is that when uclamp.min is 1024 then we should NOT choose a > big cpu then there's no disagreement about what this patch do. If that's what > you're objecting to please be more specific about how do you see this working > instead.
My point is that this patch makes the big cores the default CPUs for RT tasks which is far from being a minor change and far from being an obvious default good choice
> > If your objection is purely based on the choice of uclamp.min then while > I agree that on modern systems the little cores are good enough for the > majority of RT tasks in average Android systems. But I don't feel confident to > reach this conclusion on low end systems where the little core doesn't have > enough grunt in many cases. So I see the current default is adequate and the > responsibility of further tweaking lies within the hands of the system admin. > > -- > Qais Yousef
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