From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [RFC bpf-next] Hierarchical Cgroup Stats Collection Using BPF
Date: Wed, 16 Mar 2022 06:31:21 -1000
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To: Song Liu <song-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Alexei Starovoitov <ast-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Andrii Nakryiko <andrii-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Daniel Borkmann <daniel-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Hao Luo <haoluo-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Stanislav Fomichev <sdf-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, bpf <bpf-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, KP Singh <kpsingh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux-MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>

On Tue, Mar 15, 2022 at 11:04:56PM -0700, Song Liu wrote:
> Lookups invoke a rstat flush, so we still walk every node of a subtree for
> each lookup, no? So the actual cost should be similar than walking the
> subtree with some BPF program? Did I miss something?

rstat only walks cgroups / cpus which have been active since the flush.

Thanks.

-- 
tejun