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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> 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> X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 3870C20007 X-Stat-Signature: ruzc1xbyidcs54uiwkqq44yepep1qfro X-HE-Tag: 1725001704-243545 X-HE-Meta: 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 5oa1Vr1j H7w9MSwG6zjoM+ysi1eU/bG3/hh8GBCctop8KCnKIepmUSWLD4WaPxD79O8Yl/TCsOfdZWkLrPKZcEBlKy8rR0k4apWJfUCYLQJabDypHmfbg97GFDPjNLptJLWMs6VjFhj0c95zuIq3TI7AosbL2MogDlYZZpIcJKnppiMjgPRI5xceWxdwA5pfZvIoLuDw1+KmGeTGanS1Zzgu3A8lP1vGmWTEZjz10nVez94N9GecKfw1VNZok53vtqW34pOJ5Pa7kV99el9P9PIMgsL8MYtp+LkLvqO+LSMt2mt0viBfZnYUClFyu64+B3HzmImVyG+4A7pG7MfkjK6+nl8luUKGIPA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000026, 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 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