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[209.85.220.65]) by mx.google.com with SMTPS id d25sor6328962wmb.28.2019.03.22.15.49.48 for (Google Transport Security); Fri, 22 Mar 2019 15:49:48 -0700 (PDT) Received-SPF: pass (google.com: domain of chris@chrisdown.name designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@chrisdown.name header.s=google header.b=dzOycvFR; spf=pass (google.com: domain of chris@chrisdown.name designates 209.85.220.65 as permitted sender) smtp.mailfrom=chris@chrisdown.name; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chrisdown.name DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=Y9aDRaeIImkqbs3RD6gMjzp9RFeZ93eNkXfZogPMzV4=; b=dzOycvFR3LXcdAJzc1cZuTdB5YuJ4celv5OXmLq76bC6fhuIRBXXymUZ2X1e4X3GPz g+RHtQxVTPHKrMHRvLhSlNJtytCLr+c/sSTjz6Ejtz9K6fAOuiJqD90x+aTB17NOUbU2 C2jzjifh8zT6akDauo5+bFHj33WXlPFIZB7+0= X-Google-Smtp-Source: APXvYqwdz61zVqNkLMZqtOFJF0lk6vAo9J3Kz5QBK9eFpbbP8HIiqceSQ3TxUDoETV5aA9ODpBzhFQ== X-Received: by 2002:a1c:ac87:: with SMTP id v129mr4695169wme.72.1553294987958; Fri, 22 Mar 2019 15:49:47 -0700 (PDT) Received: from localhost ([89.36.66.5]) by smtp.gmail.com with ESMTPSA id u12sm9138257wrt.2.2019.03.22.15.49.47 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 22 Mar 2019 15:49:47 -0700 (PDT) Date: Fri, 22 Mar 2019 22:49:46 +0000 From: Chris Down To: Roman Gushchin Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Tejun Heo , Dennis Zhou , "linux-kernel@vger.kernel.org" , "cgroups@vger.kernel.org" , "linux-mm@kvack.org" , Kernel Team Subject: Re: [PATCH REBASED] mm, memcg: Make scan aggression always exclude protection Message-ID: <20190322224946.GA12527@chrisdown.name> References: <20190228213050.GA28211@chrisdown.name> <20190322160307.GA3316@chrisdown.name> <20190322222907.GA17496@tower.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190322222907.GA17496@tower.DHCP.thefacebook.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000071, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Roman Gushchin writes: >I've noticed that the old version is just wrong: if cgroup_size is way smaller >than max(min, low), scan will be set to -lruvec_size. >Given that it's unsigned long, we'll end up with scanning the whole list >(due to clamp() below). Are you certain? If so, I don't see what you mean. This is how the code looks in Linus' tree after the fixups: unsigned long cgroup_size = mem_cgroup_size(memcg); unsigned long baseline = 0; if (!sc->memcg_low_reclaim) baseline = lruvec_size; scan = lruvec_size * cgroup_size / protection - baseline; This works correctly as far as I can tell: low reclaim case: In [1]: cgroup_size=50; lruvec_size=10; protection=2000; baseline=0; lruvec_size * cgroup_size // protection - baseline Out[1]: 0 normal case: In [2]: cgroup_size=3000; lruvec_size=10; protection=2000; baseline=lruvec_size; lruvec_size * cgroup_size // protection - baseline Out[2]: 5