Re: [RFC PATCH] fs/exec: Add the support for ELF program's NUMA replication

[David Hildenbrand]

On 09.09.21 11:46, Huang Shijie wrote:
> On Mon, Sep 06, 2021 at 11:35:01AM +0200, David Hildenbrand wrote:
> > On 06.09.21 18:16, Huang Shijie wrote:
> > > This patch adds AT_NUMA_REPLICATION for execveat().
> > >
> > > If this flag is set, the kernel will trigger COW(copy on write)
> > > on the mmapped ELF binary. So the program will have a copied-page
> > > on its NUMA node, even if the original page in page cache is
> > > on other NUMA nodes.
> >
> > Am I missing something important or is this just absolutely not what we
> > want?
>
> Please see the thread:
> https://marc.info/?l=linux-kernel&m=163070220429222&w=2
>
> Linus did not think it is a good choice to implement the "per-numa node page cache"

That doesn't make this approach any better.

I don't think we want this in the kernel. If user space wants to waste 
memory, it can happily mmap() however it wants. The advisory is to not 
do it.

--
Thanks,

David / dhildenb