From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 432396B009A for ; Sat, 30 May 2009 03:20:52 -0400 (EDT) Date: Sat, 30 May 2009 09:27:58 +0200 From: Andi Kleen Subject: Re: More thoughts about hwpoison and pageflags compression Message-ID: <20090530072758.GL1065@one.firstfloor.org> References: <200905291135.124267638@firstfloor.org> <20090529225202.0c61a4b3@lxorguk.ukuu.org.uk> <20090530063710.GI1065@one.firstfloor.org> <20090529235302.ccf58d88.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090529235302.ccf58d88.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Andi Kleen , Alan Cox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, fengguang.wu@intel.com List-ID: On Fri, May 29, 2009 at 11:53:02PM -0700, Andrew Morton wrote: > On Sat, 30 May 2009 08:37:10 +0200 Andi Kleen wrote: > > > So using a separate bit is a sensible choice imho. > > Could you make the feature 64-bit-only and use one of bits 32-63? We could, but these systems can run 32bit kernels too (although it's probably not a good idea). Ok it would be probably possible to make it 64bit only, but I would prefer to not do that. Also even 32bit has still flags free and even if we run out there's an easy path to free more (see my earlier writeup) So I don't see the pressing need to conserve every bit on 32bit. > Did you consider making the poison tag external to the pageframe? Some > hash(page*) into a bitmap or something? If suitably designed, such > infrastructure could perhaps be reused to reclaim some existing page > flags. Dave Hansen had such a patch a few years back. Or maybe it > was Andy Whitcroft. I considered it at some point, but it would have complicated the code and I preferred to keep it simple. The poison handler should be relatively straight forward and do its work quickly otherwise it might not isolate the page before it's actually used. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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