Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754967AbZFCGdf (ORCPT ); Wed, 3 Jun 2009 02:33:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752268AbZFCGd2 (ORCPT ); Wed, 3 Jun 2009 02:33:28 -0400 Received: from claw.goop.org ([74.207.240.146]:50656 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752150AbZFCGd1 (ORCPT ); Wed, 3 Jun 2009 02:33:27 -0400 Message-ID: <4A261932.2020200@goop.org> Date: Wed, 03 Jun 2009 16:33:22 +1000 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Ulrich Drepper CC: Chris Mason , Ingo Molnar , Nick Piggin , "H. Peter Anvin" , Thomas Gleixner , Linux Kernel Mailing List , Andrew Morton , Linus Torvalds , Peter Zijlstra , Avi Kivity , Arjan van de Ven Subject: Re: [benchmark] 1% performance overhead of paravirt_ops on native kernels References: <4A0B62F7.5030802@goop.org> <20090525091527.GA7535@elte.hu> <4A1C3805.7060404@goop.org> <20090528061702.GB6920@wotan.suse.de> <20090530102330.GC16913@elte.hu> <20090602141802.GC3914@think> In-Reply-To: X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=UTF-8; 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: 994 Lines: 24 Ulrich Drepper wrote: > Ingo pointed to a way which doesn't negatively impact the > performance of the Xen kernel and reduces the overhead (dynamic > patching) The pvops code is already fully dynamically patched, which replaces all the indirect calls with either direct calls, inline instructions or nops. It has been this way from the initial implementation. More recently I changed the calling convention on some of the most common critical-path ops to reduce the register pressure caused by the function call clobbers; you just don't need a pile of registers to disable interrupts. Ingo knows all this, so I'm not sure what further patching he's suggesting. I don't see any more likely candidates, but I'm open to suggestions. 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/