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From: Shakeel Butt To: Vlastimil Babka Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Alexei Starovoitov , Sebastian Andrzej Siewior , Harry Yoo , Yosry Ahmed , Peter Zijlstra , Mathieu Desnoyers , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH 5/5] memcg: make memcg_rstat_updated nmi safe Message-ID: <7v2v2bwgd4jbprimygguwatdi6zhsvidibk2zlddkx7ksg3y6l@u3mlw5bw3tyt> References: <20250516064912.1515065-1-shakeel.butt@linux.dev> <20250516064912.1515065-6-shakeel.butt@linux.dev> <8114231b-ec06-44a9-9075-9ccf0809de4a@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8114231b-ec06-44a9-9075-9ccf0809de4a@suse.cz> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: 0323F1A000C X-Rspamd-Server: rspam09 X-Stat-Signature: 1gkrnfctq94d4zpups1actiwi69jhcrp X-HE-Tag: 1747409725-43188 X-HE-Meta: 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 IG1MMTC1 KfmHDao820HrFs3nnVXSFJfZcc9Z9UgER7Cbj1H8EOsppzyWRwE9GfYNBeLV29y6WU/J0ekf0cJU81tfEUQYcUkZkZWv9717CL201tFx+e6F/gn/AOB9GSxm0igYaVys0VnWJ3W2p4i8fLPWoEHpl2bsikubmoK5U6znezkNulkwtZVIcM8Y0thXgkmPPqJ+4BcA75L+tJBLtav4MUEXcLXIsKiQi3RgMf9gRxDXh4CUihGA= 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, May 16, 2025 at 11:45:39AM +0200, Vlastimil Babka wrote: > On 5/16/25 08:49, Shakeel Butt wrote: > > memcg: convert stats_updates to atomic_t > > You have two subjects, I guess delete the second one? Oops I squashed the patch at the very end and forgot to fix this. > > > Currently kernel maintains memory related stats updates per-cgroup to > > optimize stats flushing. The stats_updates is defined as atomic64_t > > which is not nmi-safe on some archs. Actually we don't really need 64bit > > atomic as the max value stats_updates can get should be less than > > nr_cpus * MEMCG_CHARGE_BATCH. A normal atomic_t should suffice. > > > > Also the function cgroup_rstat_updated() is still not nmi-safe but there > > is parallel effort to make it nmi-safe, so until then let's ignore it in > > the nmi context. > > > > Signed-off-by: Shakeel Butt > > Acked-by: Vlastimil Babka Thanks a lot.