From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 5D76F6B0265 for ; Mon, 1 Aug 2016 11:24:15 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id 1so84564543wmz.2 for ; Mon, 01 Aug 2016 08:24:15 -0700 (PDT) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id b4si31936864wjy.245.2016.08.01.08.24.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 Aug 2016 08:24:14 -0700 (PDT) Date: Mon, 1 Aug 2016 11:24:09 -0400 From: Johannes Weiner Subject: Re: [PATCH] radix-tree: account nodes to memcg only if explicitly requested Message-ID: <20160801152409.GC7603@cmpxchg.org> References: <1470057188-7864-1-git-send-email-vdavydov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1470057188-7864-1-git-send-email-vdavydov@virtuozzo.com> Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: Andrew Morton , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, Aug 01, 2016 at 04:13:08PM +0300, Vladimir Davydov wrote: > Radix trees may be used not only for storing page cache pages, so > unconditionally accounting radix tree nodes to the current memory cgroup > is bad: if a radix tree node is used for storing data shared among > different cgroups we risk pinning dead memory cgroups forever. So let's > only account radix tree nodes if it was explicitly requested by passing > __GFP_ACCOUNT to INIT_RADIX_TREE. Currently, we only want to account > page cache entries, so mark mapping->page_tree so. Is this a theoretical fix, or did you actually run into problems? I wouldn't expect any other radix tree node consumer in the kernel to come anywhere close to the page cache, so I wonder why it matters. > @@ -351,6 +351,12 @@ static int __radix_tree_preload(gfp_t gfp_mask, int nr) > struct radix_tree_node *node; > int ret = -ENOMEM; > > + /* > + * Nodes preloaded by one cgroup can be be used by another cgroup, so > + * they should never be accounted to any particular memory cgroup. > + */ > + gfp_mask &= ~__GFP_ACCOUNT; But *all* page cache radix tree nodes are allocated from inside the preload code, since the tree insertions need mapping->tree_lock. So this would effectively disable accounting of the biggest radix tree consumer in the kernel, no? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org