linux-kernel - Re: [PATCH v1 01/14] mm: introduce bpf struct ops for OOM handling

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Message-ID: <aLnFN-jJkVzL403b@slm.duckdns.org>
Date: Thu, 4 Sep 2025 06:58:31 -1000
From: Tejun Heo <tj@...nel.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Kumar Kartikeya Dwivedi <memxor@...il.com>,
	linux-mm <linux-mm@...ck.org>, bpf <bpf@...r.kernel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.com>,
	David Rientjes <rientjes@...gle.com>,
	Matt Bobrowski <mattbobrowski@...gle.com>,
	Song Liu <song@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 01/14] mm: introduce bpf struct ops for OOM handling

Hello,

On Thu, Sep 04, 2025 at 09:26:45AM -0700, Alexei Starovoitov wrote:
...
> > >>      err = test_oom__attach_cgroup(skel, cgroup_fd);
> > >>      if (CHECK_FAIL(err))
> > >>              goto cleanup;
> > >
> > > Yeah, that'd look better but are there practical differences? The only one I
> > > can think of is fs based permission check but that can be done separately
> > > too.
> >
> > The practical difference is that a single struct ops can be attached
> > to multiple cgroups.
> 
> +1
> Attaching the same scheduler to multiple cgroups also sounds useful.
> I feel sched-ext should use cgroup_fd too and do scx_sub_enable() at
> attach time instead of load time.
> Then scx_sub_disable() can happen at link detach.
> Looks more flexible from user pov.

Nothing wrong with that but I'm not sure that'd have practical
user-noticeable benefits for sched_ext. Also, would it affect how associated
programs can identify which instance they belong to? At least from sched_ext
POV, that's a lot more important than the ability to attach the same
programs in multiple places.

Thanks.

-- 
tejun