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Mon, 20 Apr 2020 10:06:51 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::1:b787]) by smtp.gmail.com with ESMTPSA id y16sm916547qtj.32.2020.04.20.10.06.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Apr 2020 10:06:51 -0700 (PDT) Date: Mon, 20 Apr 2020 13:06:50 -0400 From: Tejun Heo To: Michal Hocko Cc: Shakeel Butt , Jakub Kicinski , Andrew Morton , Linux MM , Kernel Team , Johannes Weiner , Chris Down , Cgroups Subject: Re: [PATCH 0/3] memcg: Slow down swap allocation as the available space gets depleted Message-ID: <20200420170650.GA169746@mtj.thefacebook.com> References: <20200417162355.GA43469@mtj.thefacebook.com> <20200417173615.GB43469@mtj.thefacebook.com> <20200417193539.GC43469@mtj.thefacebook.com> <20200417225941.GE43469@mtj.thefacebook.com> <20200420164740.GF43469@mtj.thefacebook.com> <20200420170318.GV27314@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200420170318.GV27314@dhcp22.suse.cz> 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: Hello, On Mon, Apr 20, 2020 at 07:03:18PM +0200, Michal Hocko wrote: > I have asked about the semantic of this know already and didn't really > get any real answer. So how does swap.high fit into high limit semantic > when it doesn't act as a limit. Considering that we cannot reclaim swap > space I find this really hard to grasp. memory.high slow down is for the case when memory reclaim can't be depended upon for throttling, right? This is the same. Swap can't be reclaimed so the backpressure is applied by slowing down the source, the same way memory.high does. It fits together with memory.low in that it prevents runaway anon allocation when swap can't be allocated anymore. It's addressing the same problem that memory.high slowdown does. It's just a different vector. Thanks. -- tejun