On 1/25/2024 6:07 PM, Dave Hansen wrote:

On 1/9/24 08:57, Artem Kuzin wrote:

quoted

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!