From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261658AbVF0AGt (ORCPT ); Sun, 26 Jun 2005 20:06:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261668AbVF0AGt (ORCPT ); Sun, 26 Jun 2005 20:06:49 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:34525 "EHLO parcelfarce.linux.theplanet.co.uk") by vger.kernel.org with ESMTP id S261658AbVF0AGr (ORCPT ); Sun, 26 Jun 2005 20:06:47 -0400 Date: Sun, 26 Jun 2005 15:31:02 -0300 From: Marcelo Tosatti To: Paul Mackerras Cc: linux-kernel@vger.kernel.org, Benjamin LaHaise Subject: Re: increased translation cache footprint in v2.6 Message-ID: <20050626183102.GA6091@logos.cnet> References: <20050626172334.GA5786@logos.cnet> <17087.15740.442831.617781@cargo.ozlabs.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17087.15740.442831.617781@cargo.ozlabs.ibm.com> User-Agent: Mutt/1.5.5.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 27, 2005 at 09:42:52AM +1000, Paul Mackerras wrote: > Marcelo Tosatti writes: > > > We've noticed a slowdown while moving from v2.4 to v2.6 on a small PPC platform > > (855T CPU running at 48Mhz, containing pair of separate I/D TLB caches with > > 32 entries each), with a relatively recent kernel (v2.6.11). > > > > Test in question is a "dd" copying 16MB from /dev/zero to RAMDISK. > > > > Pinning an 8Mbyte TLB entry at KERNELBASE brought performance back to v2.4 levels. > > Why are we not pinning a large TLB entry at KERNELBASE in 2.6? Was > that taken out to reduce the size of the tlb miss handler or > something? Paul, There are buggy instances of tlbie() destroying the 8Mbyte TLB entry - this is going to be fixed soon (its MPC8xx specific...) I worry about machines who can't pin and/or smaller number of TLB entries.