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From: Shakeel Butt To: Michal =?utf-8?Q?Koutn=C3=BD?= Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Vlastimil Babka , Alexei Starovoitov , Sebastian Andrzej Siewior , Harry Yoo , Yosry Ahmed , Peter Zijlstra , Mathieu Desnoyers , Tejun Heo , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH v4 0/5] memcg: nmi-safe kmem charging Message-ID: References: <20250519063142.111219-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: 8BA76C000C X-Rspamd-Server: rspam09 X-Stat-Signature: b3ssdq8x1oajs5s96euj57dnwudo7zf6 X-HE-Tag: 1748876090-902796 X-HE-Meta: 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 Nbvq9Zy6 KpYBhcHbqO8izTICQjiTHmsaypOK5dEn5GMVC76uc9riGTskt0xcAKgKfkGLgu3ZYeW/K8L3Um1PCKeyVetEiaevzHTv2fMUrvDTLmKdzzZR3ERcEkmWh36UHbKmdb7rubMWBwXfjCtwVmNbyl4PKuqUBMZ3tp53FQb/4Xdw+ShQZZGIeZR6Kv3NkTvgDCzCcFtHcbsWIlV1435JsgyD5aMlsx9en75+KflOAQe1uimdSABeMiPUPMlxYkg== 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 Mon, Jun 02, 2025 at 04:45:31PM +0200, Michal Koutný wrote: > Hello Shakeel. > > On Sun, May 18, 2025 at 11:31:37PM -0700, Shakeel Butt wrote: > > Users can attached their BPF programs at arbitrary execution points in > > the kernel and such BPF programs may run in nmi context. In addition, > > these programs can trigger memcg charged kernel allocations in the nmi > > context. However memcg charging infra for kernel memory is not equipped > > to handle nmi context for all architectures. > > How much memory does this refer to? Is it unbound (in particular for > non-privileged eBPF)? Or is it rather negligible? (I assume the former > to make the series worth it.) > It depends on the BPF program and thus can be arbitrarily large. So, irrespective of privileged or non-privileged BPF programs, they can allocate large amount of memory to maintain monitoring or debugging (or for some other use-case) information.