From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752234AbYIBNoK (ORCPT ); Tue, 2 Sep 2008 09:44:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751319AbYIBNn5 (ORCPT ); Tue, 2 Sep 2008 09:43:57 -0400 Received: from casper.infradead.org ([85.118.1.10]:59687 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751218AbYIBNn4 (ORCPT ); Tue, 2 Sep 2008 09:43:56 -0400 Date: Tue, 2 Sep 2008 06:43:53 -0700 From: Arjan van de Ven To: "CHADHA,VINEET" Cc: nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org, vineet@ufl.edu Subject: Re: TLB evaluation for Linux Message-ID: <20080902064353.09cf4a48@infradead.org> In-Reply-To: <1942732773.182121220328723728.JavaMail.osg@osgjas04.cns.ufl.edu> References: <1942732773.182121220328723728.JavaMail.osg@osgjas04.cns.ufl.edu> Organization: Intel X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.11; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2 Sep 2008 00:12:03 -0400 (EDT) "CHADHA,VINEET" wrote: > Hi, > > I have been working to evaluate TLB performance for Linux O/S and > virtualized workloads(such as Xen) in a Full system simulator(e.g. > simics). While my evaluation is in nascent stage, I do notice that > most of the IPIs in multi-core environments cause complete TLB > Flush. note that linux only does an ipi to processors that actually are currently running a thread of the same program (or a kernel thread). Old versions didn't do this (they also IPI'd idle processors), but on modern cpus and modern kernels that's not supposed to happen anymore (the C-states that flush the tlb anyway now do the kernel side bookkeeping as well to avoid the wakeup+useless flush) > > I want to evaluate cost of TLB shootdown including re-population > vs. each entry shootdown (invlpg). While a similar study has been > done in other kernels (e.g. L4 kernel), I am not aware if it has > been done for Linux O/S. > one of the problems is that invlpg is rather expensive; in long-ago experiments the threshold was like around a handful of pages already. At that point.. all the bookkeeping isn't likely to be a win. Esp since a tlb refill on x86 is quite cheap. -- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org