From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265550AbTGBXD5 (ORCPT ); Wed, 2 Jul 2003 19:03:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265569AbTGBXCN (ORCPT ); Wed, 2 Jul 2003 19:02:13 -0400 Received: from holomorphy.com ([66.224.33.161]:25786 "EHLO holomorphy") by vger.kernel.org with ESMTP id S265552AbTGBXAq (ORCPT ); Wed, 2 Jul 2003 19:00:46 -0400 Date: Wed, 2 Jul 2003 16:15:02 -0700 From: William Lee Irwin III To: "Martin J. Bligh" Cc: linux-kernel , Andrew Morton , haveblue@us.ibm.com Subject: Re: Overhead of highpte Message-ID: <20030702231502.GJ26348@holomorphy.com> Mail-Followup-To: William Lee Irwin III , "Martin J. Bligh" , linux-kernel , Andrew Morton , haveblue@us.ibm.com References: <574790000.1057186404@flay> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <574790000.1057186404@flay> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 02, 2003 at 03:53:24PM -0700, Martin J. Bligh wrote: > Some people were saying they couldn't see an overhead with highpte. > Seems pretty obvious to me still. It should help *more* on the NUMA > box, as PTEs become node-local. > The kmap_atomic is, of course, perfectly understandable. The increase > in the rmap functions is a bit of a mystery to me. The rmap functions perform kmap_atomic() internally while traversing pte_chains and so will take various additional TLB misses and incur various bits of computational expense with i386's kmap_atomic() semantics. The observations I made were in combination with both highpmd and an as of yet unmerged full 3-level pagetable cacheing patch. -- wli