From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 4 Apr 2007 15:38:28 -0700 (PDT) From: Christoph Lameter Subject: Re: [PATCH 1/4] x86_64: Switch to SPARSE_VIRTUAL In-Reply-To: <20070404212736.GI10084@localhost> Message-ID: 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> <1175548086.22373.99.camel@localhost.localdomain> <20070404212736.GI10084@localhost> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Bob Picco Cc: Dave Hansen , Andi Kleen , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Martin Bligh , linux-mm@kvack.org, KAMEZAWA Hiroyuki List-ID: On Wed, 4 Apr 2007, Bob Picco wrote: > Well you must have forgotten about these two postings in regards to > performance numbers: > http://marc.info/?l=linux-ia64&m=111990276501051&w=2 > and > http://marc.info/?l=linux-kernel&m=116664638611634&w=2 I am well aware of those but those were done with a PAGE_SIZE vmemmap which is particularly bad on IA64 given the TLB fault overhead. You eliminated the TLB fault overhead. Virtual Memmaps need to be designed in such a way that they do not create additional overhead. The x86_64 version here has no such overhead that you could eliminate with lookup tables. The bad thing is that this benchmark then was used to justify sparsemem on other platforms where such overhead does not exist. One needs to be careful with benchmarks..... Its better to review the code. -- 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