[PATCH v16 07/11] secretmem: use PMD-size pages to amortize direct map fragmentation

[Christoph Lameter]

On Thu, 28 Jan 2021, Michal Hocko wrote:

> > So, if I understand your concerns correct this implementation has two
> > issues:
> > 1) allocation failure at page fault that causes unrecoverable OOM and
> > 2) a possibility for an unprivileged user to deplete secretmem pool and
> > cause (1) to others
> >
> > I'm not really familiar with OOM internals, but when I simulated an
> > allocation failure in my testing only the allocating process and it's
> > parent were OOM-killed and then the system continued normally.
>
> If you kill the allocating process then yes, it would work, but your
> process might be the very last to be selected.

OOMs are different if you have a "constrained allocation". In that case it
is the fault of the process who wanted memory with certain conditions.
That memory is not available. General memory is available though. In that
case the allocating process is killed.