Messages in this thread | | | Date | Sat, 19 Jul 2014 13:31:25 -0400 (EDT) | From | Nicolas Pitre <> | Subject | Re: [PATCH 07/10] nohz: Enforce timekeeping on CPU 0 |
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On Sat, 19 Jul 2014, Frederic Weisbecker wrote:
> The timekeeper gets initialized to the value of the CPU where the > first clockevent device is setup. This works well because the timekeeper > can be any online CPU in most configs. > > Full dynticks has its own requirement though and needs the timekeeper > to always be 0. And this requirement seem to accomodate pretty well with > the above described boot timekeeper setting because the first clockevent > device happens to be initialized, most of the time, on the boot CPU > (which should be CPU 0).
This might have been discussed before... but this isn't ARM big.LITTLE friendly at all.
Could we accommodate for any arbitrary CPU instead of making CPU 0 "special" other than its role as the boot CPU please? It doesn't have to be completely dynamic, but CPU 0 might be a really bad choice for ongoing periodic duties in some configurations. For example, we might highly prefer to do this on CPU 4 for power efficiency reasons once it is online and keep CPU 0 in a deep C-state as much as possible.
Nicolas
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