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[70.44.39.90]) by smtp.gmail.com with ESMTPSA id t8sm48886qkt.125.2021.02.09.14.22.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Feb 2021 14:22:09 -0800 (PST) Date: Tue, 9 Feb 2021 17:22:08 -0500 From: Johannes Weiner To: Tim Chen Cc: Andrew Morton , Michal Hocko , Vladimir Davydov , Dave Hansen , Ying Huang , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] mm: Fix missing mem cgroup soft limit tree updates Message-ID: References: <3b6e4e9aa8b3ee1466269baf23ed82d90a8f791c.1612902157.git.tim.c.chen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3b6e4e9aa8b3ee1466269baf23ed82d90a8f791c.1612902157.git.tim.c.chen@linux.intel.com> 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 Tim, On Tue, Feb 09, 2021 at 12:29:47PM -0800, Tim Chen wrote: > @@ -6849,7 +6850,9 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) > * exclusive access to the page. > */ > > - if (ug->memcg != page_memcg(page)) { > + if (ug->memcg != page_memcg(page) || > + /* uncharge batch update soft limit tree on a node basis */ > + (ug->dummy_page && ug->nid != page_to_nid(page))) { The fix makes sense to me. However, unconditionally breaking up the batch by node can unnecessarily regress workloads in cgroups that do not have a soft limit configured, and cgroup2 which doesn't have soft limits at all. Consider an interleaving allocation policy for example. Can you please further gate on memcg->soft_limit != PAGE_COUNTER_MAX, or at least on !cgroup_subsys_on_dfl(memory_cgrp_subsys)? Thanks