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[209.85.220.65]) by mx.google.com with SMTPS id w4sor66759886pfb.13.2019.08.05.12.43.44 for (Google Transport Security); Mon, 05 Aug 2019 12:43:44 -0700 (PDT) Received-SPF: pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@cmpxchg-org.20150623.gappssmtp.com header.s=20150623 header.b="FF0ThfX/"; spf=pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=cmpxchg.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=WWvuvR2gfG7sLdu6K+RYuoog4fh46SnlfKdpfISWizo=; b=FF0ThfX/bzXj/27mCqPHlsBMwiIYZlOM9RmNphVdMiLTKFTSIINwJ461YEYbUUwEJN m26UyZ3XWL77w/tHksUHW1PeyGzJyWNY13DjAPzELJZneSPxWuZasvz9dNFt6/2JPtgv qVIywLEuv+OpFrpLPJjL+0VyhOS8hmp386H5C28ioO5TYQorFdFX3xnvENVjSQvV2tyZ q5GaWw0MT+HdTeGMxeem1WwEcjvhWzGYE8bRKhHOmp1odj0KsF0vBeTfIHRfi7j/yTkA pxF6+yVEj8pUlTHwytLp4HNKWrEMSHivN64CPzymFxxqOyFjW9elvIgLCJFiY5lCLGUn dOzg== X-Google-Smtp-Source: APXvYqxdSjvwIdE9asbvH0WVb955oASYdklotIVD6HjXgjlLwa8lAFefTwAseLg4dhaPLTUjv300/g== X-Received: by 2002:a62:6083:: with SMTP id u125mr73381751pfb.208.1565034223953; Mon, 05 Aug 2019 12:43:43 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::26a1]) by smtp.gmail.com with ESMTPSA id h26sm89520864pfq.64.2019.08.05.12.43.42 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 05 Aug 2019 12:43:43 -0700 (PDT) Date: Mon, 5 Aug 2019 15:43:41 -0400 From: Johannes Weiner To: Roman Gushchin Cc: Andrew Morton , linux-mm@kvack.org, Michal Hocko , linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH] mm: workingset: fix vmstat counters for shadow nodes Message-ID: <20190805194341.GA6260@cmpxchg.org> References: <20190801233532.138743-1-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190801233532.138743-1-guro@fb.com> User-Agent: Mutt/1.12.0 (2019-05-25) 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 Thu, Aug 01, 2019 at 04:35:32PM -0700, Roman Gushchin wrote: > Memcg counters for shadow nodes are broken because the memcg pointer is > obtained in a wrong way. The following approach is used: > virt_to_page(xa_node)->mem_cgroup > > Since commit 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup > pointer for slab pages") page->mem_cgroup pointer isn't set for slab pages, > so memcg_from_slab_page() should be used instead. > > Also I doubt that it ever worked correctly: virt_to_head_page() should be > used instead of virt_to_page(). Otherwise objects residing on tail pages > are not accounted, because only the head page contains a valid mem_cgroup > pointer. That was a case since the introduction of these counters by the > commit 68d48e6a2df5 ("mm: workingset: add vmstat counter for shadow nodes"). You're right. slub uses order-2 compound pages for radix_tree_node, so we've been underreporting shadow nodes placed in the three tail pages. Nice catch. > Fixes: 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages") > Signed-off-by: Roman Gushchin > Cc: Johannes Weiner > Cc: Andrew Morton Acked-by: Johannes Weiner