On Tue, Feb 1, 2022 at 12:08 PM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > > Currently memcg stats show several types of kernel memory: > kernel stack, page tables, sock, vmalloc, and slab. > However, there are other allocations with __GFP_ACCOUNT > (or supersets such as GFP_KERNEL_ACCOUNT) that are not accounted > in any of those stats, a few examples are: > - various kvm allocations (e.g. allocated pages to create vcpus) > - io_uring > - tmp_page in pipes during pipe_write() > - bpf ringbuffers > - unix sockets > > Keeping track of the total kernel memory is essential for the ease of > migration from cgroup v1 to v2 as there are large discrepancies between > v1's kmem.usage_in_bytes and the sum of the available kernel memory stats > in v2. Adding separate memcg stats for all __GFP_ACCOUNT kernel > allocations is an impractical maintenance burden as there a lot of those > all over the kernel code, with more use cases likely to show up in the > future. > > Therefore, add a "kernel" memcg stat that is analogous to kmem > page counter, with added benefits such as using rstat infrastructure > which aggregates stats more efficiently. Additionally, this provides a > lighter alternative in case the legacy kmem is deprecated in the future > > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> Thanks Yosry. Just to emphasize further, in our gradual migration to v2 (exposing v2 interfaces in v1 and removing v1-only interfaces), the difference between kernel memory from v1 and v2 is very prominent for some workloads. This patch will definitely ease the v2 migration. Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
