From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752958AbZI1Dga (ORCPT ); Sun, 27 Sep 2009 23:36:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752686AbZI1Dg3 (ORCPT ); Sun, 27 Sep 2009 23:36:29 -0400 Received: from mga14.intel.com ([143.182.124.37]:10283 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752466AbZI1Dg3 (ORCPT ); Sun, 27 Sep 2009 23:36:29 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,463,1249282800"; d="scan'208";a="192305794" Date: Mon, 28 Sep 2009 11:36:24 +0800 From: Wu Fengguang To: KAMEZAWA Hiroyuki Cc: Nigel Cunningham , LKML , "linux-mm@kvack.org" Subject: Re: No more bits in vm_area_struct's vm_flags. Message-ID: <20090928033624.GA11191@localhost> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090928120450.c2d8a4e2.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 28, 2009 at 11:04:50AM +0800, KAMEZAWA Hiroyuki wrote: > Hi, > > On Mon, 28 Sep 2009 12:45:35 +1000 > Nigel Cunningham wrote: > > KAMEZAWA Hiroyuki wrote: > > > On Fri, 25 Sep 2009 18:34:56 +1000 > > > Nigel Cunningham wrote: > > >> Hi. > > >> > > >> KAMEZAWA Hiroyuki wrote: > > >>>> I have some code in TuxOnIce that needs a bit too (explicitly mark the > > >>>> VMA as needing to be atomically copied, for GEM objects), and am not > > >>>> sure what the canonical way to proceed is. Should a new unsigned long be > > >>>> added? The difficulty I see with that is that my flag was used in > > >>>> shmem_file_setup's flags parameter (drm_gem_object_alloc), so that > > >>>> function would need an extra parameter too.. > > >>> Hmm, how about adding vma->vm_flags2 ? > > >> The difficulty there is that some functions pass these flags as arguments. > > >> > > > Ah yes. But I wonder some special flags, which is rarey used, can be moved > > > to vm_flags2... > > > > > > For example, > > > > > > #define VM_SEQ_READ 0x00008000 /* App will access data sequentially */ > > > #define VM_RAND_READ 0x00010000 /* App will not benefit from clustered reads */ > > > are all capsuled under > > > mm.h > > > 117 #define VM_READHINTMASK (VM_SEQ_READ | VM_RAND_READ) > > > 118 #define VM_ClearReadHint(v) (v)->vm_flags &= ~VM_READHINTMASK > > > 119 #define VM_NormalReadHint(v) (!((v)->vm_flags & VM_READHINTMASK)) > > > 120 #define VM_SequentialReadHint(v) ((v)->vm_flags & VM_SEQ_READ) > > > 121 #define VM_RandomReadHint(v) ((v)->vm_flags & VM_RAND_READ) > > > > > > Or > > > > > > 105 #define VM_PFN_AT_MMAP 0x40000000 /* PFNMAP vma that is fully mapped at mmap time */ > > > is only used under special situation. > > > > > > etc.. > > > > > > They'll be able to be moved to other(new) flag field, IIUC. > > > CCing Fengguang. > > Breif Summary of thread: > Now, vm->vm_flags has no more avialable bits. Then, I proposed Nigel > to move some flags from vm->vm_flags to other flags as vm->vm_????. > It seems readahead-hints are candidates for this...... Agreed and thanks for the summary. > > I'm working on a patch to do this, and am looking at is_mergeable_vma, > > which is invoked via can_vma_merge_after from vma_merge from > > madvise_behaviour (which potentially modifies these hint flags). Should > > those hints be considered in that function? (Do I need to pass the hints > > in as well and check they're equal?) > > I think it should be handled. Agreed. > But, yes it implies to add a new argument to several functions in mmap.c > and maybe a patch will be ugly. > > How about addding this check ? > > is_mergeable_vma(...) > .... > if (vma->vm_hints) > return 0; > > And not calling vma_merge() at madvice(ACCESS_PATTERN_HINT). > > I wonder there are little chances when madice(ACCESS_PATTERN_HINT) is > given against mapped-file-vma... Me wonder too. The access hints should be rarely used. A simple solution is reasonable for them. But what if more flags going into vm_hints in future? Thanks, Fengguang > > > > By the way, VM_ClearReadHint and VM_NormalReadHint are currently unused. > > madvise_behaviour manipulates the flags directly (in preparing > > potential replacement values). Not sure if something should be done > > about that. > > > > By the way #2, in response to the later message in this thread, I'm > > calling the new var vma->vm_hints, and have put it at the end of the > > struct at the moment. Is that a good place? > > > I think it seems nice. But please before entries under CONFIG. > How about just after vm_private_data ? > > Regards, > -Kame >