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Tue, 29 Apr 2025 17:29:11 -0700 (PDT) MIME-Version: 1.0 References: <20250428033617.3797686-1-roman.gushchin@linux.dev> <20250428033617.3797686-10-roman.gushchin@linux.dev> In-Reply-To: <20250428033617.3797686-10-roman.gushchin@linux.dev> From: Suren Baghdasaryan Date: Tue, 29 Apr 2025 17:28:59 -0700 X-Gm-Features: ATxdqUHFz_05fXYir2rslhYlMwSd6Gi_vbBqhLqf6_eQZAIUdoejhM82LlPFoTU Message-ID: Subject: Re: [PATCH rfc 09/12] sched: psi: bpf hook to handle psi events To: Roman Gushchin Cc: linux-kernel@vger.kernel.org, Andrew Morton , Alexei Starovoitov , Johannes Weiner , Michal Hocko , Shakeel Butt , David Rientjes , Josh Don , Chuyi Zhou , cgroups@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D62F040004 X-Stat-Signature: 5bjfnnqjfme4hscan4stwadiw3irnbg3 X-Rspam-User: X-HE-Tag: 1745972952-794850 X-HE-Meta: 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 3EF/Q8ji QZJVP3ACjRi+kUiNmFNuQ4v+0bSa7dgfSRti1611FocDR4kshlQSIWdFgC7zLonJ+AtF5lHuzE7Vw9WOLm2f7oY+qYaXPTvM/U1Z+rg/BNBOaJpMRGy6vTmfAiuFGqMdiQ7T0miC+UvN1rlc5Xh6MUu8Ulx6XyS31m1mZ4d89riEBfiiOr1KBYTWYpIYj93ZVFDxo 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 Sun, Apr 27, 2025 at 8:37=E2=80=AFPM Roman Gushchin wrote: > > Introduce a bpf hook to handle psi events. The primary intended > purpose of this hook is to declare OOM events based on the reaching > a certain memory pressure level, similar to what systemd-oomd and oomd > are doing in userspace. It's a bit awkward that this requires additional userspace action to create PSI triggers. I have almost no experience with BPF, so this might be a stupid question, but maybe we could provide a bpf kfunc for the BPF handler to register its PSI trigger(s) upon handler registration? > > Signed-off-by: Roman Gushchin > --- > kernel/sched/psi.c | 36 +++++++++++++++++++++++++++++++++++- > 1 file changed, 35 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c > index 1396674fa722..4c4eb4ead8f6 100644 > --- a/kernel/sched/psi.c > +++ b/kernel/sched/psi.c > @@ -176,6 +176,32 @@ static void psi_avgs_work(struct work_struct *work); > > static void poll_timer_fn(struct timer_list *t); > > +#ifdef CONFIG_BPF_SYSCALL > +__bpf_hook_start(); > + > +__weak noinline int bpf_handle_psi_event(struct psi_trigger *t) > +{ > + return 0; > +} > + > +__bpf_hook_end(); > + > +BTF_KFUNCS_START(bpf_psi_hooks) > +BTF_ID_FLAGS(func, bpf_handle_psi_event, KF_SLEEPABLE) > +BTF_KFUNCS_END(bpf_psi_hooks) > + > +static const struct btf_kfunc_id_set bpf_psi_hook_set =3D { > + .owner =3D THIS_MODULE, > + .set =3D &bpf_psi_hooks, > +}; > + > +#else > +static inline int bpf_handle_psi_event(struct psi_trigger *t) > +{ > + return 0; > +} > +#endif > + > static void group_init(struct psi_group *group) > { > int cpu; > @@ -489,6 +515,7 @@ static void update_triggers(struct psi_group *group, = u64 now, > > /* Generate an event */ > if (cmpxchg(&t->event, 0, 1) =3D=3D 0) { > + bpf_handle_psi_event(t); > if (t->of) > kernfs_notify(t->of->kn); > else > @@ -1655,6 +1682,8 @@ static const struct proc_ops psi_irq_proc_ops =3D { > > static int __init psi_proc_init(void) > { > + int err =3D 0; > + > if (psi_enable) { > proc_mkdir("pressure", NULL); > proc_create("pressure/io", 0666, NULL, &psi_io_proc_ops); > @@ -1662,9 +1691,14 @@ static int __init psi_proc_init(void) > proc_create("pressure/cpu", 0666, NULL, &psi_cpu_proc_ops= ); > #ifdef CONFIG_IRQ_TIME_ACCOUNTING > proc_create("pressure/irq", 0666, NULL, &psi_irq_proc_ops= ); > +#endif > +#ifdef CONFIG_BPF_SYSCALL > + err =3D register_btf_fmodret_id_set(&bpf_psi_hook_set); > + if (err) > + pr_err("error while registering bpf psi hooks: %d= ", err); > #endif > } > - return 0; > + return err; > } > module_init(psi_proc_init); > > -- > 2.49.0.901.g37484f566f-goog >