Messages in this thread | | | Date | Mon, 6 Jun 2022 14:32:09 +0200 | From | Michal Koutný <> | Subject | Re: [PATCH bpf-next v1 0/5] bpf: rstat: cgroup hierarchical stats |
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On Fri, Jun 03, 2022 at 12:47:19PM -0700, Yosry Ahmed <yosryahmed@google.com> 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
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