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Wed, 20 Aug 2025 16:56:12 -0700 (PDT) MIME-Version: 1.0 References: <20250818170136.209169-1-roman.gushchin@linux.dev> <20250818170136.209169-13-roman.gushchin@linux.dev> <87tt23vt8u.fsf@linux.dev> <87cy8qx50g.fsf@linux.dev> In-Reply-To: <87cy8qx50g.fsf@linux.dev> From: Suren Baghdasaryan Date: Wed, 20 Aug 2025 16:56:01 -0700 X-Gm-Features: Ac12FXwHFX4DgL6ZNVWka_tcMoj1Wu2SMzrvjJmRsLac3uNbaTN5z0M9dFMR-KA Message-ID: Subject: Re: [PATCH v1 12/14] sched: psi: implement psi trigger handling using bpf To: Roman Gushchin Cc: linux-mm@kvack.org, bpf@vger.kernel.org, Johannes Weiner , Michal Hocko , David Rientjes , Matt Bobrowski , Song Liu , Kumar Kartikeya Dwivedi , Alexei Starovoitov , Andrew Morton , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 6zmdbhxx43pgt8s9ig6joi6oq8k1s14r X-Rspam-User: X-Rspamd-Queue-Id: 28D90C0012 X-Rspamd-Server: rspam05 X-HE-Tag: 1755734174-869263 X-HE-Meta: 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 72BEPKl9 2uKZZ69XgYN2lGA/qulYmZHwp9LCi4SbZjo8eU6IrpyW+ba7FsAR0nyvAJ/GV24u3CTW6yHQTxz5rPUt9JzUnYshoembizovFZKcGnPJs1Jj/ifDVlvpGUq12rf578otziYXgxYQFrdaGcSosnAgeuCWLSXjCsuOPnAu3CLF6qWmJwBPDMrjBmJ8YW9lonz9P6uc0Es6ldkAEGjdqlHCJmOYA8Tr8cOqBAdflU0JW2JcK0rA1JSd/FD41vcexeGio1ihU 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 Tue, Aug 19, 2025 at 4:31=E2=80=AFPM Roman Gushchin wrote: > > Roman Gushchin writes: > > > Suren Baghdasaryan writes: > > > >> On Mon, Aug 18, 2025 at 10:02=E2=80=AFAM Roman Gushchin > >> wrote: > > > >> > >>> + > >>> + /* Cgroup Id */ > >>> + u64 cgroup_id; > >> > >> This cgroup_id field is weird. It's not initialized and not used here, > >> then it gets initialized in the next patch and used in the last patch > >> from a selftest. This is quite confusing. Also logically I don't think > >> a cgroup attribute really belongs to psi_trigger... Can we at least > >> move it into bpf_psi where it might fit a bit better? > > > > I can't move it to bpf_psi, because a single bpf_psi might own multiple > > triggers with different cgroup_id's. > > For sure I can move it to the next patch, if it's preferred. > > > > If you really don't like it here, other option is to replace it with > > a new bpf helper (kfunc) which calculates the cgroup_id by walking the > > trigger->group->cgroup->cgroup_id path each time. > > Actually there is no easy path from psi_group to cgroup, so there is > no such option available, unfortunately. Or we need a back-link from > the psi_group to cgroup. Ok, I obviously missed some important relations between these structures. Let me digest it some more before commenting further.