Re: [PATCH v2] kvm, mm: account shadow page tables to kmemcg

Shakeel Butt
2018-06-29T16:47:51Z

On Fri, Jun 29, 2018 at 7:55 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Fri 29-06-18 16:40:23, Paolo Bonzini wrote:
> > On 29/06/2018 16:30, Michal Hocko wrote:
> > > I am not familiar wtih kvm to judge but if we are going to account this
> > > memory we will probably want to let oom_badness know how much memory
> > > to account to a specific process. Is this something that we can do?
> > > We will probably need a new MM_KERNEL rss_stat stat for that purpose.
> > >
> > > Just to make it clear. I am not opposing to this patch but considering
> > > that shadow page tables might consume a lot of memory it would be good
> > > to know who is responsible for it from the OOM perspective. Something to
> > > solve on top of this.
> >
> > The amount of memory is generally proportional to the size of the
> > virtual machine memory, which is reflected directly into RSS. Because
> > KVM processes are usually huge, and will probably dwarf everything else
> > in the system (except firefox and chromium of course :)), the general
> > order of magnitude of the oom_badness should be okay.
>
> I think we will need MM_KERNEL longterm anyway. As I've said this is not
> a must for this patch to go. But it is better to have a fair comparision
> and kill larger processes if at all possible. It seems this should be
> the case here.
>

I will look more into MM_KERNEL counter. I still have couple more kmem
allocations in kvm (like dirty bitmap) which I want to be accounted. I
will bundle them together.

thanks,
Shakeel