linux-kernel - Re: [PATCH 0/4] memcg: nmi-safe kmem charging

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Message-Id: <20250509182632.8ab2ba932ca5e0f867d21fc2@linux-foundation.org>
Date: Fri, 9 May 2025 18:26:32 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song
 <muchun.song@...ux.dev>, Vlastimil Babka <vbabka@...e.cz>, Alexei
 Starovoitov <ast@...nel.org>, Sebastian Andrzej Siewior
 <bigeasy@...utronix.de>, bpf@...r.kernel.org, linux-mm@...ck.org,
 cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, Meta kernel team
 <kernel-team@...a.com>
Subject: Re: [PATCH 0/4] memcg: nmi-safe kmem charging

On Fri,  9 May 2025 16:28:55 -0700 Shakeel Butt <shakeel.butt@...ux.dev> wrote:

> BPF programs can trigger memcg charged kernel allocations in nmi
> context. However memcg charging infra for kernel memory is not equipped
> to handle nmi context. This series adds support for kernel memory
> charging for nmi context.

The patchset adds quite a bit of material to core MM on behalf of a
single caller.  So can we please take a close look at why BPF is doing
this?

What would be involved in changing BPF to avoid doing this, or of
changing BPF to handle things locally?  What would be the end-user
impact of such an alteration?  IOW, what is the value to our users of
the present BPF behavior?