From: Hao Luo <haoluo@google.com>
To: Tejun Heo <tj@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shuah Khan <shuah@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Michal Hocko <mhocko@kernel.org>,
Stanislav Fomichev <sdf@google.com>,
David Rientjes <rientjes@google.com>,
Greg Thelen <gthelen@google.com>,
Shakeel Butt <shakeelb@google.com>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [RFC PATCH bpf-next 8/9] bpf: Introduce cgroup iter
Date: Tue, 10 May 2022 15:49:59 -0700 [thread overview]
Message-ID: <CA+khW7gUdZQq77jO2_A6rvE6f+HV=sGfBVGvAmazGPvwudE0RQ@mail.gmail.com> (raw)
In-Reply-To: <YnriMPYyOP9ibskc@slm.duckdns.org>
On Tue, May 10, 2022 at 3:07 PM Tejun Heo <tj@kernel.org> wrote:
>
> Hello,
>
> On Tue, May 10, 2022 at 02:12:16PM -0700, Hao Luo wrote:
> > > Is there a reason why this can't be a proper iterator which supports
> > > lseek64() to locate a specific cgroup?
> > >
> >
> > There are two reasons:
> >
> > - Bpf_iter assumes no_llseek. I haven't looked closely on why this is
> > so and whether we can add its support.
> >
> > - Second, the name 'iter' in this patch is misleading. What this patch
> > really does is reusing the functionality of dumping in bpf_iter.
> > 'Dumper' is a better name. We want to create one file in bpffs for
> > each cgroup. We are essentially just iterating a set of one single
> > element.
>
> I see. I'm just shooting in the dark without context but at least in
> principle there's no reason why cgroups wouldn't be iterable, so it might be
> something worth at least thinking about before baking in the interface.
>
Yep. Conceptually there should be no problem to iterate cgroups in the
system. It may be better to have two independent bpf objects: bpf_iter
and bpf_dumper. In our use case, we want bpf_dumper, which just
exports data out through fs interface.
Hao
next prev parent reply other threads:[~2022-05-10 22:50 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-10 0:17 [RFC PATCH bpf-next 0/9] bpf: cgroup hierarchical stats collection Yosry Ahmed
2022-05-10 0:17 ` [RFC PATCH bpf-next 1/9] bpf: introduce CGROUP_SUBSYS_RSTAT program type Yosry Ahmed
2022-05-10 18:07 ` Yosry Ahmed
2022-05-10 19:21 ` Yosry Ahmed
2022-05-10 18:44 ` Tejun Heo
2022-05-10 19:34 ` Yosry Ahmed
2022-05-10 19:59 ` Tejun Heo
2022-05-10 20:43 ` Yosry Ahmed
2022-05-10 21:01 ` Tejun Heo
2022-05-10 21:55 ` Yosry Ahmed
2022-05-10 22:09 ` Tejun Heo
2022-05-10 22:10 ` Yosry Ahmed
2022-05-10 0:18 ` [RFC PATCH bpf-next 2/9] cgroup: bpf: flush bpf stats on rstat flush Yosry Ahmed
2022-05-10 18:45 ` Tejun Heo
2022-05-10 0:18 ` [RFC PATCH bpf-next 3/9] libbpf: Add support for rstat progs and links Yosry Ahmed
2022-05-10 0:18 ` [RFC PATCH bpf-next 4/9] bpf: add bpf rstat helpers Yosry Ahmed
2022-05-10 0:18 ` [RFC PATCH bpf-next 5/9] bpf: add bpf_map_lookup_percpu_elem() helper Yosry Ahmed
2022-05-10 0:18 ` [RFC PATCH bpf-next 6/9] cgroup: add v1 support to cgroup_get_from_id() Yosry Ahmed
2022-05-10 18:33 ` Tejun Heo
2022-05-10 18:36 ` Yosry Ahmed
2022-05-10 0:18 ` [RFC PATCH bpf-next 7/9] cgroup: Add cgroup_put() in !CONFIG_CGROUPS case Yosry Ahmed
2022-05-10 18:25 ` Hao Luo
2022-05-10 0:18 ` [RFC PATCH bpf-next 8/9] bpf: Introduce cgroup iter Yosry Ahmed
2022-05-10 18:25 ` Hao Luo
2022-05-10 18:54 ` Tejun Heo
2022-05-10 21:12 ` Hao Luo
2022-05-10 22:07 ` Tejun Heo
2022-05-10 22:49 ` Hao Luo [this message]
2022-05-10 0:18 ` [RFC PATCH bpf-next 9/9] selftest/bpf: add a selftest for cgroup hierarchical stats Yosry Ahmed
2022-05-13 7:16 ` [RFC PATCH bpf-next 0/9] bpf: cgroup hierarchical stats collection Yosry Ahmed
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