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From: Yosry Ahmed To: Shakeel Butt Cc: JP Kobryn , tj@kernel.org, mhocko@kernel.org, hannes@cmpxchg.org, akpm@linux-foundation.org, linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 1/4 v2] cgroup: move cgroup_rstat from cgroup to cgroup_subsys_state Message-ID: References: <20250227215543.49928-1-inwardvessel@gmail.com> <20250227215543.49928-2-inwardvessel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6440EC0010 X-Stat-Signature: t8kamgx3u1twn3ygtj31napzmy4szhnt X-HE-Tag: 1741026115-790836 X-HE-Meta: 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 YpcvZUTg ooJgGrsqXCyerAEBWbBaflmMqebPPw0ATlSDQGOp6PH5pxEC23hgD8t8yjSup94f1n6GhAOeeAdtNXmYexsUw1F7j2e5NRDr+o5hyL6UuQCMOVutWs9SmwoEL7mbWl0N5dA62LOd16sEGWJdYBZsqrqAWegDyoVokDgNV2/yZkL9gXVeIin+zoRQxCqBKhj0sgkHoqNZW4k90TajEodaNdBNTWmZq+1k327iGPnq0+hxBRmYT7oVaIY2S5TFXr6Fgp8ifu8sZcwG0y7Q= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 03, 2025 at 10:18:33AM -0800, Shakeel Butt wrote: > On Sat, Mar 01, 2025 at 01:25:03AM +0000, Yosry Ahmed wrote: > > On Fri, Feb 28, 2025 at 05:06:23PM -0800, JP Kobryn wrote: > [...] > > > > > > > > We should call bpf_rstat_flush() only if (!pos->ss) as well, right? > > > > Otherwise we will call BPF rstat flush whenever any subsystem is > > > > flushed. > > > > > > > > I guess it's because BPF can now pass any subsystem to > > > > cgroup_rstat_flush(), and we don't keep track. I think it would be > > > > better if we do not allow BPF programs to select a css and always make > > > > them flush the self css. > > > > > > > > We can perhaps introduce a bpf_cgroup_rstat_flush() wrapper that takes > > > > in a cgroup and passes cgroup->self internally to cgroup_rstat_flush(). > > > > > > I'm fine with this if others are in agreement. A similar concept was > > > done in v1. > > > > Let's wait for Shakeel to chime in here since he suggested removing this > > hook, but I am not sure if he intended to actually do it or not. Better > > not to waste effort if this will be gone soon anyway. > > > > Yes, let's remove this unused hook. JP, can you please followup after > this series with the removal/deprecation of this? In this case I think it's fine for the purpose of this series to keep bpf_rstat_flush() called if any css is being flushed to keep things simple. > One thing we might want to careful about is if in future someone to > add this functionality again, that would not be a clean revert but > what Yosry is asking for. Not sure what you mean here, I am not asking for anything :P