From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) by kanga.kvack.org (Postfix) with ESMTP id 881CC6B000A for ; Fri, 2 Nov 2018 13:48:28 -0400 (EDT) Received: by mail-pg1-f199.google.com with SMTP id f22-v6so2327377pgv.21 for ; Fri, 02 Nov 2018 10:48:28 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id u66-v6si35316559pgu.94.2018.11.02.10.48.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Nov 2018 10:48:27 -0700 (PDT) Date: Fri, 2 Nov 2018 18:48:23 +0100 From: Michal Hocko Subject: Re: Will the recent memory leak fixes be backported to longterm kernels? Message-ID: <20181102174823.GI28039@dhcp22.suse.cz> References: <20181102005816.GA10297@tower.DHCP.thefacebook.com> <20181102073009.GP23921@dhcp22.suse.cz> <20181102154844.GA17619@tower.DHCP.thefacebook.com> <20181102161314.GF28039@dhcp22.suse.cz> <20181102162237.GB17619@tower.DHCP.thefacebook.com> <20181102165147.GG28039@dhcp22.suse.cz> <20181102172547.GA19042@tower.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181102172547.GA19042@tower.DHCP.thefacebook.com> Sender: owner-linux-mm@kvack.org List-ID: To: Roman Gushchin Cc: Dexuan Cui , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Kernel Team , Shakeel Butt , Johannes Weiner , Tejun Heo , Rik van Riel , Konstantin Khlebnikov , Matthew Wilcox , "Stable@vger.kernel.org" On Fri 02-11-18 17:25:58, Roman Gushchin wrote: > On Fri, Nov 02, 2018 at 05:51:47PM +0100, Michal Hocko wrote: > > On Fri 02-11-18 16:22:41, Roman Gushchin wrote: [...] > > > 2) We do forget to scan the last page in the LRU list. So if we ended up with > > > 1-page long LRU, it can stay there basically forever. > > > > Why > > /* > > * If the cgroup's already been deleted, make sure to > > * scrape out the remaining cache. > > */ > > if (!scan && !mem_cgroup_online(memcg)) > > scan = min(size, SWAP_CLUSTER_MAX); > > > > in get_scan_count doesn't work for that case? > > No, it doesn't. Let's look at the whole picture: > > size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); > scan = size >> sc->priority; > /* > * If the cgroup's already been deleted, make sure to > * scrape out the remaining cache. > */ > if (!scan && !mem_cgroup_online(memcg)) > scan = min(size, SWAP_CLUSTER_MAX); > > If size == 1, scan == 0 => scan = min(1, 32) == 1. > And after proportional adjustment we'll have 0. My friday brain hurst when looking at this but if it doesn't work as advertized then it should be fixed. I do not see any of your patches to touch this logic so how come it would work after them applied? -- Michal Hocko SUSE Labs