On Fri, Jun 03, 2022 at 12:47:19PM -0700, Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > In short, think of these bpf maps as equivalents to "struct > memcg_vmstats" and "struct memcg_vmstats_percpu" in the memory > controller. They are just containers to store the stats in, they do > not have any subgraph structure and they have no use beyond storing > percpu and total stats. Thanks for the explanation. > I run small microbenchmarks that are not worth posting, they compared > the latency of bpf stats collection vs. in-kernel code that adds stats > to struct memcg_vmstats[_percpu] and flushes them accordingly, the > difference was marginal. OK, that's a reasonable comparison. > The main reason for this is to provide data in a similar fashion to > cgroupfs, in text file per-cgroup. I will include this clearly in the > next cover message. Thanks, it'd be great to have that use-case captured there. > AFAIK loading bpf programs requires a privileged user, so someone has > to approve such a program. Am I missing something? A sysctl unprivileged_bpf_disabled somehow stuck in my head. But as I wrote, this adds a way how to call cgroup_rstat_updated() directly, it's not reserved for privilged users anyhow. > bpf_iter_run_prog() is used to run bpf iterator programs, and it grabs > rcu read lock before doing so. So AFAICT we are good on that front. Thanks for the clarification. Michal
