From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e36.co.us.ibm.com (8.13.8/8.13.8) with ESMTP id l32L8BNa032669 for ; Mon, 2 Apr 2007 17:08:11 -0400 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v8.3) with ESMTP id l32L8Bxt031572 for ; Mon, 2 Apr 2007 15:08:11 -0600 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l32L8AmX019955 for ; Mon, 2 Apr 2007 15:08:11 -0600 Subject: Re: [PATCH 1/4] x86_64: Switch to SPARSE_VIRTUAL From: Dave Hansen In-Reply-To: References: <20070401071024.23757.4113.sendpatchset@schroedinger.engr.sgi.com> <20070401071029.23757.78021.sendpatchset@schroedinger.engr.sgi.com> <200704011246.52238.ak@suse.de> <1175544797.22373.62.camel@localhost.localdomain> Content-Type: text/plain Date: Mon, 02 Apr 2007 14:08:06 -0700 Message-Id: <1175548086.22373.99.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Andi Kleen , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Martin Bligh , linux-mm@kvack.org, KAMEZAWA Hiroyuki List-ID: On Mon, 2007-04-02 at 13:30 -0700, Christoph Lameter wrote: > On Mon, 2 Apr 2007, Dave Hansen wrote: > > I completely agree, it looks like it should be faster. The code > > certainly has potential benefits. But, to add this neato, apparently > > more performant feature, we unfortunately have to add code. Adding the > > code has a cost: code maintenance. This isn't a runtime cost, but it is > > a real, honest to goodness tradeoff. > > Its just the opposite. The vmemmap code is so efficient that we can remove > lots of other code and gops of these alternate implementations. We do want to make sure that there isn't anyone relying on these. Are you thinking of simple sparsemem vs. extreme vs. sparsemem vmemmap? Or, are you thinking of sparsemem vs. discontig? > On x86_64 > its even superior to FLATMEM since FLATMEM still needs a memory reference > for the mem_map area. So if we make SPARSE standard for all > configurations then there is no need anymore for FLATMEM DISCONTIG etc > etc. Can we not cleanup all this mess? Get rid of all the gazillions > of #ifdefs please? This would ease code maintenance significantly. I hate > having to constantly navigate my way through all the alternatives. Amen, brother. I'd love to see DISCONTIG die, with sufficient testing, of course. Andi, do you have any ideas on how to get sparsemem out of the 'experimental' phase? I have noticed before that sparsemem should be able to cover the flatmem case if we make MAX_PHYSMEM_BITS == SECTION_SIZE_BITS and massage from there. -- Dave -- 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