Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760020AbZAWAIb (ORCPT ); Thu, 22 Jan 2009 19:08:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755985AbZAWAIX (ORCPT ); Thu, 22 Jan 2009 19:08:23 -0500 Received: from gw.goop.org ([64.81.55.164]:43797 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753589AbZAWAIW (ORCPT ); Thu, 22 Jan 2009 19:08:22 -0500 Message-ID: <49790A6F.1080000@goop.org> Date: Thu, 22 Jan 2009 16:08:15 -0800 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: "H. Peter Anvin" CC: Zachary Amsden , Nick Piggin , Ingo Molnar , Linux Kernel Mailing List , Linus Torvalds , "jeremy@xensource.com" , "chrisw@sous-sol.org" , "rusty@rustcorp.com.au" , Andrew Morton , Xen-devel Subject: Re: lmbench lat_mmap slowdown with CONFIG_PARAVIRT 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> <1232663311.16317.176.camel@bodhitayantram.eng.vmware.com> <4978F6C6.3090003@goop.org> <4978F7DC.1040503@zytor.com> <1232665120.16317.186.camel@bodhitayantram.eng.vmware.com> <497906A4.2030008@zytor.com> In-Reply-To: <497906A4.2030008@zytor.com> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 858 Lines: 19 H. Peter Anvin wrote: > Right now a number of the call sites contain a huge push/pop sequence > followed by an indirect call. We can patch in the native code to > avoid the branch overhead, but the register constraints and icache > footprint is unchanged. That's true for the pvops hooks emitted in the .S files, but not so true for ones in C code (well, there are no explicit push/pops, but the presence of the call may cause the compiler to generate them). The .S hooks can definitely be cleaned up, but I don't think that's germane to Nick's observations that the mm code is showing slowdowns. J -- 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/