linux-kernel - Re: [PATCH rfc 09/12] sched: psi: bpf hook to handle psi events

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Message-ID: <aBF1sPtO_UbE1fYo@google.com>
Date: Wed, 30 Apr 2025 00:58:24 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	David Rientjes <rientjes@...gle.com>, Josh Don <joshdon@...gle.com>,
	Chuyi Zhou <zhouchuyi@...edance.com>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, bpf@...r.kernel.org
Subject: Re: [PATCH rfc 09/12] sched: psi: bpf hook to handle psi events

On Tue, Apr 29, 2025 at 05:28:59PM -0700, Suren Baghdasaryan wrote:
> On Sun, Apr 27, 2025 at 8:37 PM Roman Gushchin <roman.gushchin@...ux.dev> 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?

It looks like it's doable using struct_ops path: the .init callback
can create psi triggers and "attach" them to the loaded bpf program.
But I need to figure out the details.

Good point, thank you!