Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751020AbVKDQIU (ORCPT ); Fri, 4 Nov 2005 11:08:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751012AbVKDQIU (ORCPT ); Fri, 4 Nov 2005 11:08:20 -0500 Received: from smtp.osdl.org ([65.172.181.4]:64973 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751020AbVKDQIT (ORCPT ); Fri, 4 Nov 2005 11:08:19 -0500 Date: Fri, 4 Nov 2005 08:07:47 -0800 (PST) From: Linus Torvalds To: Andy Nelson cc: mingo@elte.hu, akpm@osdl.org, arjan@infradead.org, arjanv@infradead.org, haveblue@us.ibm.com, kravetz@us.ibm.com, lhms-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mbligh@mbligh.org, mel@csn.ul.ie, nickpiggin@yahoo.com.au, pj@sgi.com Subject: Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19 In-Reply-To: <20051104153903.E5D561845FF@thermo.lanl.gov> Message-ID: References: <20051104153903.E5D561845FF@thermo.lanl.gov> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1513 Lines: 39 On Fri, 4 Nov 2005, Andy Nelson wrote: > > AFAIK, mips chips have a software TLB refill that takes 1000 > cycles more or less. I could be wrong. You're not far off. Time it on a real machine some day. On a modern x86, you will fill a TLB entry in anything from 1-8 cycles if it's in L1, and add a couple of dozen cycles for L2. In fact, the L1 TLB miss can often be hidden by the OoO engine. Now, do the math. Your "3-4 time slowdown" with several hundred cycle TLB miss just GOES AWAY with real hardware. Yes, you'll still see slowdowns, but they won't be nearly as noticeable. And having a simpler and more efficient kernel will actually make _up_ for them in many cases. For example, you can do all your calculations on idle workstations that don't mysteriously just crash because somebody was also doing something else on them. Face it. MIPS sucks. It was clean, but it didn't perform very well. SGI doesn't sell those things very actively these days, do they? So don't blame Linux. Don't make sweeping statements based on hardware situations that just aren't relevant any more. If you ever see a machine again that has a huge TLB slowdown, let the machine vendor know, and then SWITCH VENDORS. Linux will work on sane machines too. Linus - 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/