Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932193AbZJANwe (ORCPT ); Thu, 1 Oct 2009 09:52:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756320AbZJANwd (ORCPT ); Thu, 1 Oct 2009 09:52:33 -0400 Received: from smtp2.ultrahosting.com ([74.213.174.253]:43630 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756236AbZJANwd (ORCPT ); Thu, 1 Oct 2009 09:52:33 -0400 Date: Thu, 1 Oct 2009 09:47:35 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Hugh Dickins cc: KAMEZAWA Hiroyuki , Wu Fengguang , Nigel Cunningham , LKML , "linux-mm@kvack.org" Subject: Re: No more bits in vm_area_struct's vm_flags. In-Reply-To: Message-ID: References: <4AB9A0D6.1090004@crca.org.au> <20090924100518.78df6b93.kamezawa.hiroyu@jp.fujitsu.com> <4ABC80B0.5010100@crca.org.au> <20090925174009.79778649.kamezawa.hiroyu@jp.fujitsu.com> <4AC0234F.2080808@crca.org.au> <20090928120450.c2d8a4e2.kamezawa.hiroyu@jp.fujitsu.com> <20090928033624.GA11191@localhost> <20090928125705.6656e8c5.kamezawa.hiroyu@jp.fujitsu.com> <20090929105735.06eea1ee.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1402 Lines: 33 On Thu, 1 Oct 2009, Hugh Dickins wrote: > Are we doing that? If you have some example like, when PG_slab is set > then PG_owner_priv_1 means such-and-such, but if not not: okay, I'm > fine with that. Look at how compound pages are handled in include/linux/page-flags.h > But if you're saying something like, if PG_reclaim is set at the same > time as PG_buddy, then they mean the page is not a buddy or under > reclaim, but brokenbacked: then I'm a bit (or even 32 bits) worried. Of course you need to be careful not to use two bits that can be used indepedently. > > VM_HUGETLB cannot grow up and down f.e. and there are > > certainly lots of other impossible combinations that can be used to put > > more information into the flags. > > Where it makes sense, where it's understandable, okay: there may be a > few which could naturally use combinations. But in general, no, I > think we'd be asking for endless maintenance trouble if we change the > meaning of some flags according to other flags. We made the page flags stuff configurable. On 64 bit we use more flags, on 32 bit we compress the page flags a bit. Maybe do the same for vm_flags? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/