From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754609AbcBHGCF (ORCPT ); Mon, 8 Feb 2016 01:02:05 -0500 Received: from gum.cmpxchg.org ([85.214.110.215]:57354 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750961AbcBHGBz (ORCPT ); Mon, 8 Feb 2016 01:01:55 -0500 Date: Mon, 8 Feb 2016 01:01:36 -0500 From: Johannes Weiner To: Vladimir Davydov Cc: Andrew Morton , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/5] radix-tree: account radix_tree_node to memory cgroup Message-ID: <20160208060136.GD22202@cmpxchg.org> References: <886d4b42a50c77c45ece9c0e685fc25f8f7643c9.1454864628.git.vdavydov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <886d4b42a50c77c45ece9c0e685fc25f8f7643c9.1454864628.git.vdavydov@virtuozzo.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Feb 07, 2016 at 08:27:34PM +0300, Vladimir Davydov wrote: > Allocation of radix_tree_node objects can be easily triggered from > userspace, so we should account them to memory cgroup. Besides, we need > them accounted for making shadow node shrinker per memcg (see > mm/workingset.c). > > A tricky thing about accounting radix_tree_node objects is that they are > mostly allocated through radix_tree_preload(), so we can't just set > SLAB_ACCOUNT for radix_tree_node_cachep - that would likely result in a > lot of unrelated cgroups using objects from each other's caches. > > One way to overcome this would be making radix tree preloads per memcg, > but that would probably look cumbersome and overcomplicated. > > Instead, we make radix_tree_node_alloc() first try to allocate from the > cache with __GFP_ACCOUNT, no matter if the caller has preloaded or not, > and only if it fails fall back on using per cpu preloads. This should > make most allocations accounted. > > Signed-off-by: Vladimir Davydov Acked-by: Johannes Weiner I'm not too stoked about the extra slab call. But the preload call allocates nodes for the worst-case insertion, so you are absolutely right that charging there would not make sense for cgroup ownership. And I can't think of anything better to do here.