Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Tejun Heo <htejun@gmail.com>
Date:   Thu, 28 Jul 2022 07:35:14 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Hao Luo <haoluo@google.com>
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>,
        Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Shuah Khan <shuah@kernel.org>,
        Michal Hocko <mhocko@kernel.org>,
        KP Singh <kpsingh@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        John Fastabend <john.fastabend@gmail.com>,
        Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        David Rientjes <rientjes@google.com>,
        Stanislav Fomichev <sdf@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: [PATCH bpf-next v5 4/8] bpf: Introduce cgroup iter
Message-ID: <YuLI0jh8Csq0mErM@slm.duckdns.org>
References: <20220722174829.3422466-1-yosryahmed@google.com>
 <20220722174829.3422466-5-yosryahmed@google.com>
 <YuK+eg3lgwJ2CJnJ@slm.duckdns.org>
 <CA+khW7gfzoeHVd5coTSWXuYVfqiVMwoSjXkWsP-CeVdmOm0FqA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CA+khW7gfzoeHVd5coTSWXuYVfqiVMwoSjXkWsP-CeVdmOm0FqA@mail.gmail.com>
Precedence: bulk

On Thu, Jul 28, 2022 at 10:20:46AM -0700, Hao Luo wrote:
...
> is a good feature of this convention. My thoughts: It seems that ID
> may be better, for two reasons. First, because ID is stateless, the
> userspace doesn't have to remember closing the FD. Second, using
> different identifications in two directions (userspace specifies
> cgroup using FD, while kernel reports cgroup using ID) introduces a
> little complexity when connecting them together.

Yeah, you can pass the IDs around different processes, print and log them in
meaningful ways and so on because they're actual IDs, so my preference is
towards using them for anything new.

Thanks.

-- 
tejun