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[109.81.82.19]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3749ee9c188sm3158578f8f.55.2024.08.30.00.08.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Aug 2024 00:08:23 -0700 (PDT) Date: Fri, 30 Aug 2024 09:08:22 +0200 From: Michal Hocko To: Liu Jing Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: The percpu memory used by memcg cannot be cleared Message-ID: References: <20240829170644.15588-1-liujing@cmss.chinamobile.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240829170644.15588-1-liujing@cmss.chinamobile.com> On Fri 30-08-24 01:06:44, Liu Jing wrote: > hello，linux boss > > I found a problem in the process of using linux memcg，When I turned swap off, the memcg memory I created with the following script could not be deleted with echo 0 > memory.force_empty, as explained below。 > > ---------------------------------------------------------------------------------------------------------- > step1：swapoff -a > > > step2：use this script to create memcg > > #!/bin/bash > mkdir -p /tmp/test > for i in 'seq 2000' > do > sudo mkdir -p /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i} > sudo echo $$ > /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i}/tasks > sudo echo 'data' > /tmp/test/test$ {i} > sudo echo $$ > /sys/fs/cgroup/memory/user.slice/user-0.slice/tasks > sudo rmdir /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i} > done [...] I assume you /tmp is tmpfs backed. > Therefore, I want to know why swap affects memcg memory reclamation, > echo 0 > memory.force_empty this interface should force the memory > used by the cgroup to be reclaimed. If the above is true then you simply do not have any backing storage to reclaim to. You need swap to reclaim tmpfs/shmem memory. -- Michal Hocko SUSE Labs