On Mon, Jul 04, 2022 at 05:12:54PM +0200, Michal Hocko wrote: > On Fri 01-07-22 20:35:21, Roman Gushchin 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. > > So I guess this will be a GFP_ATOMIC request failing due to the hard > limit, right? I think it would be easier to understand if the specific > allocation request type was mentioned. It all started from the discussion here: https://www.spinics.net/lists/linux-mm/msg302319.html Please, take a look. > > > 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. So the cgroup can > > significantly exceed the memory.max limit without even triggering > > MEMCG_MAX events. > > More on that in other reply. > > > Fix this by making sure that we never enforce allocations without > > raising a MEMCG_MAX event. > > > > Reported-by: Yafang Shao <laoar.shao@xxxxxxxxx> > > Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx> > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > > Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> > > Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx> > > Cc: cgroups@xxxxxxxxxxxxxxx > > Cc: linux-mm@xxxxxxxxx > > Cc: bpf@xxxxxxxxxxxxxxx > > The patch makes sense to me though even without the weird charge to a > dead memcg aspect. It is true that a very calm memcg can trigger the > even much later after a GFP_ATOMIC charge (or __GFP_HIGH in general) > fails. Good point! > > Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks!
