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b=ErIWNpYqkcqsxM+6XhEBHioSO4BSy2GdXycbHxGuYxRyI7TcDv8EWg5IQv8p19V3E c1Kk2rSN8N1i/rpbwyR5GGWgU3uk+0XvBxzB6xijkNQbiHU1wYI9L7RcUU/8zVLAL3 BEw2KTmp6++ckQxBYqyL5BDwKh8P7/YhkNNz5m/Q= Date: Fri, 9 May 2025 18:26:32 -0700 From: Andrew Morton To: Shakeel Butt Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Vlastimil Babka , Alexei Starovoitov , Sebastian Andrzej Siewior , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH 0/4] memcg: nmi-safe kmem charging Message-Id: <20250509182632.8ab2ba932ca5e0f867d21fc2@linux-foundation.org> In-Reply-To: <20250509232859.657525-1-shakeel.butt@linux.dev> References: <20250509232859.657525-1-shakeel.butt@linux.dev> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 879601C0002 X-Stat-Signature: ryizf4ddjjb45cf6h8x4tmrhpcr1e5cb X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1746840394-179170 X-HE-Meta: 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 Lw9rstYH R1Oazho6gdmqV644Z7BiOv11RkCKSVYzyGPQiTf+yb00TeQSZwJ8HBpyE4Gp4/DeFuUlB1im8yWlFX3Z7wflEIUgJubqgA44bq+X7bfqM52H+DGCO2WCdOcARUBjFUcD/U+h0f6Eg4aELIDoIX1C5hawlMygCUzt44AR6qyhGgMj0heCMIJ7Jr6Wfs/n3lUO6PXBaTi1lVpW0DviNUNdM8KyPwI5clQOVNgqfw7CZZmAp31I= 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 Fri, 9 May 2025 16:28:55 -0700 Shakeel Butt 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?