From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 023656B01EE for ; Wed, 7 Apr 2010 02:03:52 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o3763oXB006561 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 7 Apr 2010 15:03:50 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id E1CC745DE79 for ; Wed, 7 Apr 2010 15:03:49 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id B1C1745DE7A for ; Wed, 7 Apr 2010 15:03:49 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 909A5E18006 for ; Wed, 7 Apr 2010 15:03:49 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 3D402E18004 for ; Wed, 7 Apr 2010 15:03:46 +0900 (JST) From: KOSAKI Motohiro Subject: Re: Arch specific mmap attributes (Was: mprotect pgprot handling weirdness) In-Reply-To: <1270592111.13812.88.camel@pasglop> References: <20100406185246.7E63.A69D9226@jp.fujitsu.com> <1270592111.13812.88.camel@pasglop> Message-Id: <20100407095145.FB70.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Date: Wed, 7 Apr 2010 15:03:45 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Benjamin Herrenschmidt Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, "linux-kernel@vger.kernel.org" , linux-arch@vger.kernel.org List-ID: > On Tue, 2010-04-06 at 19:26 +0900, KOSAKI Motohiro wrote: > > > Ok, I see. No biggie. The main deal remains how we want to do that > > > inside the kernel :-) I think the less horrible options here are > > > to either extend vm_flags to always be 64-bit, or add a separate > > > vm_map_attributes flag, and add the necessary bits and pieces to > > > prevent merge accross different attribute vma's. > > > > vma->vm_flags already have VM_SAO. Why do we need more flags? > > At least, I dislike to add separate flags member into vma. > > It might introduce unnecessary messy into vma merge thing. > > Well, we did shove SAO in there, and used up the very last vm_flag for > it a while back. Now I need another one, for little endian mappings. So > I'm stuck. > > But the problem goes further I believe. Archs do nowadays have quite an > interesting set of MMU attributes that it would be useful to expose to > some extent. Generally speaking, It seems no good idea. desktop and server world don't interest arch specific mmu attribute crap. because many many opensource and ISV library don't care it. I know highend hpc and embedded have differenct eco-system. they might want to use such strange mmu feature. I recommend to you are focusing popwerpc eco-system. I'm not against changing kernel internal. I only disagree mmu attribute fashion will be become used widely. > > Some powerpc's also provide storage keys for example and I think ARM > have something along those lines. There's interesting cachability > attributes too, on x86 as well. Being able to use such attributes to > request for example a relaxed ordering mapping on x86 might be useful. > > I think it basically boils down to either extend vm_flags to always be > 64-bit, which seems to be Nick preferred approach, or introduct a > vm_attributes with all the necessary changes to the merge code to take > it into account (not -that- hard tho, there's only half a page of > results in grep for these things :-) -- 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