Messages in this thread |  | | Date | Mon, 6 Jan 2014 17:21:45 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC] sched: CPU topology try |
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On Wed, Dec 18, 2013 at 02:13:51PM +0100, Vincent Guittot wrote: > This patch applies on top of the two patches [1][2] that have been proposed by > Peter for creating a new way to initialize sched_domain. It includes some minor > compilation fixes and a trial of using this new method on ARM platform. > [1] https://lkml.org/lkml/2013/11/5/239 > [2] https://lkml.org/lkml/2013/11/5/449 > > Based on the results of this tests, my feeling about this new way to init the > sched_domain is a bit mitigated.
Yay :-)
> We can add more levels that will describe other dependency/independency like > the frequency scaling dependency and as a result the final sched_domain > topology will have additional levels (if they have not been removed during > the degenerate sequence)
Yeah, this 'creative' use of degenerate domains is pretty neat ;-)
> My concern is about the configuration of the table that is used to create the > sched_domain. Some levels are "duplicated" with different flags configuration > which make the table not easily readable and we must also take care of the > order because parents have to gather all cpus of its childs. So we must > choose which capabilities will be a subset of the other one. The order is > almost straight forward when we describe 1 or 2 kind of capabilities > (package ressource sharing and power sharing) but it can become complex if we > want to add more.
I think I see what you're saying, although I hope that won't actually happen in real hardware -- that said, people do tend to do crazy with these ARM chips :/
We should also try and be conservative in the topology flags we want to add, which should further reduce the amount of pain here.
For now I do think this is a viable approach.. Yes its a bit cumbersome for these asymmetric systems but it does give us enough to start playing.
I yet have to read Morton's emails on the P and C states, will try to have a look at those tomorrow with a hopefully fresher brain -- somehow its the end of the day already..
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