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Thu, 02 Mar 2023 11:52:12 -0800 (PST) X-Google-Smtp-Source: AK7set9F1G6JtF5DGOq6j8cbXWBmcpu8b83cZrJwsXL9wg3gwV4tF1cFLK0Rsx6WeyshNzx3NRsVBQ== X-Received: by 2002:a05:600c:46c9:b0:3d2:392e:905f with SMTP id q9-20020a05600c46c900b003d2392e905fmr8479899wmo.24.1677786732690; Thu, 02 Mar 2023 11:52:12 -0800 (PST) Received: from vschneid.remote.csb ([154.57.232.159]) by smtp.gmail.com with ESMTPSA id p14-20020a05600c468e00b003eb369abd92sm4702803wmo.2.2023.03.02.11.52.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Mar 2023 11:52:12 -0800 (PST) From: Valentin Schneider To: Michal Hocko Cc: Sebastian Andrzej Siewior , cgroups@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Johannes Weiner , Michal =?utf-8?Q?Koutn=C3=BD?= , Peter Zijlstra , Thomas Gleixner , Vladimir Davydov , Waiman Long , Roman Gushchin , Shakeel Butt Subject: Re: [PATCH v5 2/6] mm/memcg: Disable threshold event handlers on PREEMPT_RT In-Reply-To: References: <20220226204144.1008339-1-bigeasy@linutronix.de> <20220226204144.1008339-3-bigeasy@linutronix.de> Date: Thu, 02 Mar 2023 19:52:11 +0000 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspamd-Queue-Id: 109B6120013 X-Stat-Signature: bspwkoqbk8cauxonfk3934yduigmzhaa X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1677786735-297800 X-HE-Meta: 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 +fjYc2dI FMMdz2zQFjr/ZqaT981H9ldHJtBv0KI8ztQCk4coqgpIbqgODe0AhxYgzLq8zC9sU43V1jF/TP3BEI5+Jlh2/J5lpqWTZAp4Gq/vcAYCiF0sRhj89bLr9MLFtlm9AOdXl1DQ+n4+PjSkKE9Z1Zjxi2EeKTM4ozd648t9bIKy6oF+dim7UZdARu3yNkh5PIHtxdaqyaUrStlfr09OH8lbT7PZIl4IG85BdV1SKpbWcfXpUQsnH313aWNx9pO48MlB71MnDw5kKuDbz7r6fkgJldtaiyrYClSiNSrbO+b+Xig5l15MWxWmLTbH5qHKoUXfM1N3+IghkGxrdS4xVtjN3Cd8kRKHWYC787DtOndh9KKJ6nZovT0KrvvASB5NKgSkzlo4/qoTmivUsTBiH1d4xXDM8SfLUQAghkWxq X-Bogosity: Ham, tests=bogofilter, spamicity=0.000787, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 02/03/23 14:34, Valentin Schneider wrote: > On 02/03/23 13:56, Michal Hocko wrote: >> What I am trying to evaluate here is whether it makes sense to support >> and maintain a non-trivial code for something that might be working >> sub-optimally or even not working properly in some corner cases. The >> price for the maintenance is certainly not free. > > That's also what I'm trying to make sense of. Either way this will be > frankenkernel territory, the cgroupv1 ship has already sailed for upstream > IMO. So, if someone ends up in a similar situation and considers kludging those notifications back in: Don't. Have a look at: memcg_check_events() `\ mem_cgroup_threshold() `\ __mem_cgroup_threshold() `\ eventfd_signal() Having IRQs off, percpu reads, and the the eventfd signal is a nice recipe for disaster. The OOM notification sits outside of that, but any other memcg notification will cause pain.