Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758501AbYCYRua (ORCPT ); Tue, 25 Mar 2008 13:50:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756702AbYCYRuN (ORCPT ); Tue, 25 Mar 2008 13:50:13 -0400 Received: from relay1.sgi.com ([192.48.171.29]:34010 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755195AbYCYRuL (ORCPT ); Tue, 25 Mar 2008 13:50:11 -0400 Date: Tue, 25 Mar 2008 10:48:19 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: David Miller cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, torvalds@linux-foundation.org Subject: Re: larger default page sizes... In-Reply-To: <20080324.144356.104645106.davem@davemloft.net> Message-ID: References: <20080324.133722.38645342.davem@davemloft.net> <20080324.144356.104645106.davem@davemloft.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1101 Lines: 28 On Mon, 24 Mar 2008, David Miller wrote: > We should fix the underlying problems. > > I'm hitting issues on 128 cpu Niagara2 boxes, and it's all fundamental > stuff like contention on the per-zone page allocator locks. > > Which is very fixable, without going to larger pages. No its not fixable. You are doing linear optimizations to a slowdown that grows exponentially. Going just one order up for page size reduces the necessary locks and handling of the kernel by 50%. > > powerpc also runs HPC codes. They certainly see the same results > > that we see. > > There are ways to get large pages into the process address space for > compute bound tasks, without suffering the well known negative side > effects of using larger pages for everything. These hacks have limitations. F.e. they do not deal with I/O and require application changes. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/