Re: [PATCH] mm: memcontrol: do not miss MEMCG_MAX events for enforced allocations

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On Sat, Jul 2, 2022 at 8:39 AM Roman Gushchin <roman.gushchin@xxxxxxxxx> wrote:
>
> On Fri, Jul 01, 2022 at 10:50:40PM -0700, Shakeel Butt wrote:
> > On Fri, Jul 1, 2022 at 8:35 PM Roman Gushchin <roman.gushchin@xxxxxxxxx> wrote:
> > >
> > > Yafang Shao reported an issue related to the accounting of bpf
> > > memory: if a bpf map is charged indirectly for memory consumed
> > > from an interrupt context and allocations are enforced, MEMCG_MAX
> > > events are not raised.
> > >
> > > It's not/less of an issue in a generic case because consequent
> > > allocations from a process context will trigger the reclaim and
> > > MEMCG_MAX events. However a bpf map can belong to a dying/abandoned
> > > memory cgroup, so it might never happen.
> >
> > The patch looks good but the above sentence is confusing. What might
> > never happen? Reclaim or MAX event on dying memcg?
>
> Direct reclaim and MAX events. I agree it might be not clear without
> looking into the code. How about something like this?
>
> "It's not/less of an issue in a generic case because consequent
> allocations from a process context will trigger the direct reclaim
> and MEMCG_MAX events will be raised. However a bpf map can belong
> to a dying/abandoned memory cgroup, so there will be no allocations
> from a process context and no MEMCG_MAX events will be triggered."
>

SGTM and you can add:

Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>



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