From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 4 Nov 2005 08:07:47 -0800 (PST) From: Linus Torvalds 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: owner-linux-mm@kvack.org Return-Path: 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 List-ID: 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, 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