On Tue, Aug 25, 2020 at 06:56:46AM -0300, Daniel Henrique Barboza wrote: > > > On 8/24/20 8:49 PM, David Gibson wrote: > > On Mon, Aug 24, 2020 at 08:45:12AM -0300, Daniel Henrique Barboza wrote: > > > > > > > > [...] > > > > > > LOPAPR support a somewhat asymmetrical NUMA setup in its current > > > > > form, > > > > > > > > Huh, I didn't even realize that. What's the mechanism? > > > > > > LOPAPR mentions that a single resource/node can have multiple > > > associativity > > > arrays. The idea is to contemplate the situations where the node has > > > more than one connection with the board. > > > > > > I say "somewhat" because, right after mentioning that, the spec also says > > > that > > > the OS should consider that the distance between two nodes must always be > > > the shortest one of all available arrays. I'll copy/paste the except here > > > (end of section 15.2, "Numa Resource Associativity": > > > > Ah. I didn't think that's what "asymmetric NUMA" meant... but come to > > think of it, I'm not very sure about that. > > > This was a poor attempt of my part to cut PAPR some slack. > > TBH, even if current PAPR allows for some form of NUMA asymmetry, I don't > think > it's worth implementing at all. It'll be more complexity on top of what I > already added here, and the best case scenario will be the kernel ignoring it > (worst case - kernel blowing it up because we're adding more associativity > arrays in each CPU and so on).
Yes, I agree.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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