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Tue, 20 Oct 2020 11:19:59 -0700 (PDT) Date: Tue, 20 Oct 2020 14:18:22 -0400 From: Johannes Weiner To: Roman Gushchin Cc: Michal =?iso-8859-1?Q?Koutn=FD?= , Richard Palethorpe , ltp@lists.linux.it, Andrew Morton , Shakeel Butt , Christoph Lameter , Michal Hocko , Tejun Heo , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko Subject: Re: [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root Message-ID: <20201020181822.GA397401@cmpxchg.org> References: <20201014190749.24607-1-rpalethorpe@suse.com> <20201016094702.GA95052@blackbook> <20201016145308.GA312010@cmpxchg.org> <20201016171502.GA102311@blackbook> <20201019222845.GA64774@carbon.dhcp.thefacebook.com> <20201020162714.GC46039@blackbook> <20201020170717.GA153102@carbon.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201020170717.GA153102@carbon.DHCP.thefacebook.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: On Tue, Oct 20, 2020 at 10:07:17AM -0700, Roman Gushchin wrote: > If we want these counter to function properly, then we should go into the opposite > direction and remove the special handling of the root memory cgroup in many places. I suspect this is also by far the most robust solution from a code and maintenance POV. I don't recall the page counter at the root level having been a concern in recent years, even though it's widely used in production environments. It's lockless and cache compact. It's also per-cpu batched, which means it isn't actually part of the memcg hotpath.