Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759053AbZAVW2a (ORCPT ); Thu, 22 Jan 2009 17:28:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754050AbZAVW2Q (ORCPT ); Thu, 22 Jan 2009 17:28:16 -0500 Received: from smtp-outbound-1.vmware.com ([65.115.85.69]:39248 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753595AbZAVW2P (ORCPT ); Thu, 22 Jan 2009 17:28:15 -0500 Subject: Re: lmbench lat_mmap slowdown with CONFIG_PARAVIRT From: Zachary Amsden To: Jeremy Fitzhardinge Cc: Nick Piggin , Ingo Molnar , Linux Kernel Mailing List , Linus Torvalds , "hpa@zytor.com" , "jeremy@xensource.com" , "chrisw@sous-sol.org" , "rusty@rustcorp.com.au" , Andrew Morton , Xen-devel In-Reply-To: <4977A051.8050203@goop.org> References: <20090120110542.GE19505@wotan.suse.de> <20090120112634.GA20858@elte.hu> <20090120140324.GA26424@elte.hu> <49763806.5090009@goop.org> <20090120205653.GA19710@elte.hu> <20090121072718.GN24891@wotan.suse.de> <4977A051.8050203@goop.org> Content-Type: text/plain Date: Thu, 22 Jan 2009 14:28:31 -0800 Message-Id: <1232663311.16317.176.camel@bodhitayantram.eng.vmware.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1312 Lines: 32 On Wed, 2009-01-21 at 14:23 -0800, Jeremy Fitzhardinge wrote: > Nick Piggin wrote: > > Oh, _llc_ references/misses? Ouch. > > > > You have, what 32K L1I, 32K L1D, and 4MB L2? And even this microbenchmark > > is seeing increased L2 misses by nearly 3%. Hmm, I wonder where that is > > coming from? Instruction fetches? > > > > I assume so. There should be no extra data accesses with > CONFIG_PARAVIRT (hm, there's probably some extra stack/spill traffic, > but I surely hope that's not falling out of cache). These fragments, from native_pgd_val, certainly don't help: c0120f60: 55 push %ebp c0120f61: 89 e5 mov %esp,%ebp c0120f63: 5d pop %ebp c0120f64: c3 ret c0120f65: 8d 74 26 00 lea 0x0(%esi,%eiz,1),%esi c0120f69: 8d bc 27 00 00 00 00 lea 0x0(%edi,%eiz,1),%edi That is really disgusting. We absolutely should be patching away the function calls here in the native case.. not sure we do that today. Zach -- 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/