On Tue, Jun 23, 2020 at 11:47 AM Roman Gushchin <guro@xxxxxx> wrote: > > Percpu memory is becoming more and more widely used by various subsystems, > and the total amount of memory controlled by the percpu allocator can make > a good part of the total memory. > > As an example, bpf maps can consume a lot of percpu memory, and they are > created by a user. Also, some cgroup internals (e.g. memory controller > statistics) can be quite large. On a machine with many CPUs and big > number of cgroups they can consume hundreds of megabytes. > > So the lack of memcg accounting is creating a breach in the memory > isolation. Similar to the slab memory, percpu memory should be accounted > by default. > > To implement the perpcu accounting it's possible to take the slab memory > accounting as a model to follow. Let's introduce two types of percpu > chunks: root and memcg. What makes memcg chunks different is an > additional space allocated to store memcg membership information. If > __GFP_ACCOUNT is passed on allocation, a memcg chunk should be be used. > If it's possible to charge the corresponding size to the target memory > cgroup, allocation is performed, and the memcg ownership data is recorded. > System-wide allocations are performed using root chunks, so there is no > additional memory overhead. > > To implement a fast reparenting of percpu memory on memcg removal, we > don't store mem_cgroup pointers directly: instead we use obj_cgroup API, > introduced for slab accounting. > > Signed-off-by: Roman Gushchin <guro@xxxxxx> > Acked-by: Dennis Zhou <dennis@xxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
