Re: [PATCH RFC 02/12] mm: add config option and per-NUMA node VMS support

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On 1/25/2024 6:07 PM, Dave Hansen wrote:
> On 1/9/24 08:57, Artem Kuzin wrote:
>> We already have per-NUMA node init_mm, but this is not enough.
>> We need this array of pointers in the task struct due to the proper pgd 
>> (per-NUMA node) should be used for threads of process that occupy more 
>> than one NUMA node.
> Let me repeat what Christoph said in a bit more forceful way.
>
> MAX_NUMNODES can be 1024.  You're adding 1023*8 bytes of overhead for
> each process ... everywhere, including on my single node laptop.  That's
> completely unacceptable.  You need to find another way to do this.
>
> I'd suggest just ignoring the problem for now.  Do multi-node processes
> with a later optimization.

Hi Dave, thanks to you and Christoph for the comments. I've just gave some details why this is necessary, and didn't want to push the solution with MAX_NUMNODES forward, this is temporarily
thing and this place should be definitely updated in future.

As for possible options, for now I am thinking about two:
1. additional config option to limit the number of page tables and corresponding replicas
2. setup per-NUMA node page tables and replicas in a lazy way allocating them on demand

But here I need to try and test everything.

Thanks!





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