Re: [PATCH] mm/vmalloc: make vm_struct.nr_pages an unsigned long

[Matthew Wilcox]

On Wed, Jul 29, 2026 at 08:57:08PM +0300, Artem Lytkin wrote:
> A vmalloc area can hold more than 2^32 pages, but the page counts

I had a "wait, what, really?" moment.  And it can!  2^32 pages is 16TiB,
and x86-64 says:

   ffffc90000000000 |  -55    TB | ffffe8ffffffffff |   32 TB | vmalloc/ioremap space (vmalloc_base)

So we can have _one_ allocation that is more than 2^32 pages.  But I'm
not sure where we'll get the memory to populate it from.
https://blogs.oracle.com/cloud-infrastructure/announcing-oci-compute-e6-acceleron-instances
says I can get 2.3TB of memory in a single machine, which is a factor of
8 away from where we'd need to be to actually hit this.

Intel are adveertising a max memory of 1.5TiB on the 6990E+ (128GiB *
12 channels).  So if you put 8 Xeons in a box and loaded it up, that
could get you to 12TiB.

I'm not saying we shouldn't fix this, but it's all theoretical for now,
right?