Re: [LSF/MM/BPF BoF Session] Numa-Aware Placement for Page Cache Pages

[Gregory Price <gourry@gourry.net>]

On Sun, May 03, 2026 at 12:00:48AM +0100, Matthew Wilcox wrote:
> On Sat, May 02, 2026 at 03:57:19PM +0100, Gregory Price wrote:
> > On Thu, Apr 30, 2026 at 02:15:19PM +0100, Matthew Wilcox wrote:
> > > Ideally, no, the kernel should observe the task and get it right.
> > 
> > Out of curiosity, a use case i've been exploring is something like
> > 
> > fd = open()
> > buf = mmap(fd, ...)
> > mbind(buf, device_node)
> > /* fault file pages directly onto device memory */
> 
> Could you be explicit what _kind_ of node you're talking about here?
> My initial thought went to something like DAX where the node actually
> contains persistent memory and the fd is a reference to some chunk
> of that storage.  But I don't think that's what you're referring to.
> You might be thinking about a presentation of DRAM over the CXL fabric.
> Or you might be thinking about memory presented by a graphics card
> (perhaps over CXL, perhaps some other way).  The meaning of "device
> memory" has become thoroughly confused (thanks Jerome!) so I sincerely
> don't know what you're talking about.
>

Ah, I can see how the language has moved over time.

But yes a gpu with onboard memory presented as a NUMA node, or some
other accelerator where the kernel is responsible for managing its
memory (rather than a driver).

Probably the use-case needs a bit more consideration before we go
dangling new policies off the page cache - just chewing on ideas.

~Gregory