From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751818AbdJIGYa (ORCPT ); Mon, 9 Oct 2017 02:24:30 -0400 Received: from mx2.suse.de ([195.135.220.15]:36650 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751361AbdJIGY3 (ORCPT ); Mon, 9 Oct 2017 02:24:29 -0400 Date: Mon, 9 Oct 2017 08:24:26 +0200 From: Michal Hocko To: Shakeel Butt Cc: Alexander Viro , Vladimir Davydov , Greg Thelen , Andrew Morton , Linux MM , linux-fsdevel@vger.kernel.org, LKML Subject: Re: [PATCH] fs, mm: account filp and names caches to kmemcg Message-ID: <20171009062426.hmqedtqz5hkmhnff@dhcp22.suse.cz> References: <20171005222144.123797-1-shakeelb@google.com> <20171006075900.icqjx5rr7hctn3zd@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 06-10-17 12:33:03, Shakeel Butt wrote: > >> names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0, > >> - SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); > >> + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); > > > > I might be wrong but isn't name cache only holding temporary objects > > used for path resolution which are not stored anywhere? > > > > Even though they're temporary, many containers can together use a > significant amount of transient uncharged memory. We've seen machines > with 100s of MiBs in names_cache. Yes that might be possible but are we prepared for random ENOMEM from vfs calls which need to allocate a temporary name? > > >> filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, > >> - SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); > >> + SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL); > >> percpu_counter_init(&nr_files, 0, GFP_KERNEL); > >> } > > > > Don't we have a limit for the maximum number of open files? > > > > Yes, there is a system limit of maximum number of open files. However > this limit is shared between different users on the system and one > user can hog this resource. To cater that, we set the maximum limit > very high and let the memory limit of each user limit the number of > files they can open. Similarly here. Are all syscalls allocating a fd prepared to return ENOMEM? -- Michal Hocko SUSE Labs