On 10/29/24 11:18 PM, Alistair Popple wrote:
John Hubbard <jhubbard@xxxxxxxxxx> writes:
On 10/29/24 9:42 PM, Christoph Hellwig wrote:
On Tue, Oct 29, 2024 at 09:39:15PM -0700, John Hubbard wrote:
...
Because pinning down these amounts of memoryt is completely insane.
I don't mind the switch to kvmalloc, but we need to put in an upper
bound of what can be pinned.
I'm wondering though, how it is that we decide how much of the user's
system we prevent them from using? :) People with hardware accelerators
do not always have page fault capability, and yet these troublesome
users insist on stacking their system full of DRAM and then pointing
the accelerator to it.
How would we choose a value? Memory sizes keep going up...
The obvious answer is you let users decide. I did have a patch series to
do that via a cgroup[1]. However I dropped that series mostly because I
couldn't find any users of such a limit to provide feedback on how they
would use it or how they wanted it to work.
Trawling through the discussion there, I see that Jason Gunthorpe mentioned:
"Things like VFIO & KVM use cases effectively pin 90% of all system memory"
...which means that we'll be able to get that in-tree call trace that
Christoph
is asking for, pretty soon. No GPUs required. :)
thanks,
--
John Hubbard
- Alistair
[1] - https://lore.kernel.org/linux-mm/cover.c238416f0e82377b449846dbb2459ae9d7030c8e.1675669136.git-series.apopple@xxxxxxxxxx/
