Ping!
-- Ethan
Ethan Solomita wrote:
> Andi Kleen wrote:
>
>> On Monday 12 March 2007 23:51, Ethan Solomita wrote:
>>
>>> This patch corrects inconsistent use of node numbers (variously "nid" or
>>> "node") in the presence of fake NUMA.
>>>
>> I think it's very consistent -- your patch would make it inconsistent though.
>>
>
> It's consistent to call node_online() with a physical node ID when the
> online node mask is composed of fake nodes?
>
>
>> Sorry, but when you ask for NUMA emulation you will get it. I don't see
>> any point in a "half way only for some subsystems I like" NUMA emulation.
>> It's unlikely that your ideas of where it is useful and where is not
>> matches other NUMA emulation user's ideas too.
>>
>
> I don't understand your comments. My code is intended to work for all
> systems. If the system is non-NUMA by nature, then all CPUs map to fake
> node 0.
>
> As an example, on a two chip dual-core AMD opteron system, there are 4
> "cpus" where CPUs 0 and 1 are close to the first half of memory, and
> CPUs 2 and 3 are close to the second half. Without this change CPUs 2
> and 3 are mapped to fake node 1. This results in awful performance. With
> this change, CPUs 2 and 3 are mapped to (roughly) 1/2 the fake node
> count. Their zonelists[] are ordered to do allocations preferentially
> from zones that are local to CPUs 2 and 3.
>
> Can you tell me the scenario where my code makes things worse?
>
>
>> Besides adding such a secondary node space would be likely a huge long term
>> mainteance issue. I just can it see breaking with every non trivial change.
>>
>
> I'm adding no data structures to do this. The current code already has
> get_phys_node. My changes use the existing information about node
> layout, both the physical and fake, and defines a mapping. The current
> mapping just takes a physical node and says "it's the fake node too".
>
>
>> NACK.
>>
>
> I wish you would include some specifics as to why you think what you
> do. You're suggesting we leave in place a system that destroys NUMA
> locality when using fake numa, and passes around physical node ids as an
> index into nodes[] whihc is indexed by fake nodes. My change has no
> effect without fake numa, and harms no one with fake numa.
> -- Ethan
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