From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx110.postini.com [74.125.245.110]) by kanga.kvack.org (Postfix) with SMTP id F04B66B0002 for ; Wed, 27 Mar 2013 11:32:22 -0400 (EDT) Date: Wed, 27 Mar 2013 16:32:20 +0100 From: Michal Hocko Subject: Re: [PATCH] memcg: fix memcg_cache_name() to use cgroup_name() Message-ID: <20130327153220.GL16579@dhcp22.suse.cz> References: <1364373399-17397-1-git-send-email-mhocko@suse.cz> <20130327145727.GD29052@cmpxchg.org> <20130327151104.GK16579@dhcp22.suse.cz> <51530E1E.3010100@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51530E1E.3010100@parallels.com> Sender: owner-linux-mm@kvack.org List-ID: To: Glauber Costa Cc: Johannes Weiner , Tejun Heo , Li Zefan , KAMEZAWA Hiroyuki , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Wed 27-03-13 19:19:58, Glauber Costa wrote: > On 03/27/2013 07:11 PM, Michal Hocko wrote: > > On Wed 27-03-13 10:58:25, Johannes Weiner wrote: > >> On Wed, Mar 27, 2013 at 09:36:39AM +0100, Michal Hocko wrote: > > [...] > >>> + /* > >>> + * kmem_cache_create_memcg duplicates the given name and > >>> + * cgroup_name for this name requires RCU context. > >>> + * This static temporary buffer is used to prevent from > >>> + * pointless shortliving allocation. > >>> + */ > >>> + if (!tmp_name) { > >>> + tmp_name = kmalloc(PAGE_SIZE, GFP_KERNEL); > >>> + WARN_ON_ONCE(!tmp_name); > >> > >> Just use the page allocator directly and get a free allocation failure > >> warning. > > > > WARN_ON_ONCE is probably pointless. > > > >> Then again, order-0 pages are considered cheap enough that they never > >> even fail in our current implementation. > >> > >> Which brings me to my other point: why not just a simple single-page > >> allocation? > > > > No objection from me. I was previously thinking about the "proper" > > size for something that is a file name. So I originally wanted to use > > PATH_MAX instead but ended up with PAGE_SIZE for reasons I do not > > remember now. > > theoretically, this is PATH_MAX + max cache name. So do you prefer kmalloc(PATH_MAX) or the page allocator directly as Johannes suggests? I agree tha kamlloc(PAGE_SIZE) looks weird. -- Michal Hocko SUSE Labs -- 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