Re: [PATCH bpf-next v7 06/34] bpf: prepare for memcg-based memory accounting for bpf maps
From: Song Liu <hidden>
Date: 2020-11-20 01:06:03
Also in:
bpf, linux-mm, lkml
On Nov 19, 2020, at 9:37 AM, Roman Gushchin [off-list ref] wrote:
In the absolute majority of cases if a process is making a kernel
allocation, it's memory cgroup is getting charged.
Bpf maps can be updated from an interrupt context and in such
case there is no process which can be charged. It makes the memory
accounting of bpf maps non-trivial.
Fortunately, after commit 4127c6504f25 ("mm: kmem: enable kernel
memcg accounting from interrupt contexts") and b87d8cefe43c
("mm, memcg: rework remote charging API to support nesting")
it's finally possible.
To do it, a pointer to the memory cgroup of the process, which created
the map, is saved, and this cgroup can be charged for all allocations
made from an interrupt context. This commit introduces 2 helpers:
bpf_map_kmalloc_node() and bpf_map_alloc_percpu(). They can be used in
the bpf code for accounted memory allocations, both in the process and
interrupt contexts. In the interrupt context they're using the saved
memory cgroup, otherwise the current cgroup is getting charged.
Signed-off-by: Roman Gushchin <redacted>Acked-by: Song Liu <redacted> [...]