From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx162.postini.com [74.125.245.162]) by kanga.kvack.org (Postfix) with SMTP id A18F76B0062 for ; Fri, 8 Jun 2012 20:57:00 -0400 (EDT) Message-ID: <1339203416.6893.10.camel@dabdike.int.hansenpartnership.com> Subject: Re: [PATCH 2/4] Add a __GFP_SLABMEMCG flag From: James Bottomley Date: Sat, 09 Jun 2012 09:56:56 +0900 In-Reply-To: References: <1339148601-20096-1-git-send-email-glommer@parallels.com> <1339148601-20096-3-git-send-email-glommer@parallels.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Glauber Costa , cgroups@vger.kernel.org, linux-mm@kvack.org, Tejun Heo , Frederic Weisbecker , devel@openvz.org, kamezawa.hiroyu@jp.fujitsu.com, Pekka Enberg , Michal Hocko , Johannes Weiner , Suleiman Souhlal On Fri, 2012-06-08 at 14:31 -0500, Christoph Lameter wrote: > On Fri, 8 Jun 2012, Glauber Costa wrote: > > > */ > > #define __GFP_NOTRACK_FALSE_POSITIVE (__GFP_NOTRACK) > > > > -#define __GFP_BITS_SHIFT 25 /* Room for N __GFP_FOO bits */ > > +#define __GFP_BITS_SHIFT 26 /* Room for N __GFP_FOO bits */ > > #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) > > Please make this conditional on CONFIG_MEMCG or so. The bit can be useful > in particular on 32 bit architectures. I really don't think that's at all a good idea. It's asking for trouble when we don't spot we have a flag overlap. It also means that we're trusting the reuser to know that their use case can never clash with CONFIG_MEMGC and I can't think of any configuration where this is possible currently. I think making the flag define of __GFP_SLABMEMCG conditional might be a reasonable idea so we get a compile failure if anyone tries to use it when !CONFIG_MEMCG. James -- 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