From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751193AbdFAOIb (ORCPT ); Thu, 1 Jun 2017 10:08:31 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:35392 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751096AbdFAOI3 (ORCPT ); Thu, 1 Jun 2017 10:08:29 -0400 Subject: Re: [RFC PATCH 00/10] x86: undwarf unwinder To: Ingo Molnar , Josh Poimboeuf Cc: x86@kernel.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, Linus Torvalds , Andy Lutomirski , "H. Peter Anvin" , Peter Zijlstra , Mel Gorman References: <20170601060824.wv2go3adbvx5ptmt@gmail.com> <20170601115819.3twoowcnvtrfzjzr@treble> <20170601135005.zf2lidtgslfvyihs@gmail.com> From: Jiri Slaby Message-ID: <3db1be2a-cc33-89f3-950f-cfe1c21ee7f1@suse.cz> Date: Thu, 1 Jun 2017 16:08:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <20170601135005.zf2lidtgslfvyihs@gmail.com> Content-Type: text/plain; charset=iso-8859-2 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ccing Mel who did proper measurements and can hopefully comment on his results. On 06/01/2017, 03:50 PM, Ingo Molnar wrote: > That's not what I meant! The speedup comes from (hopefully) being able to disable > CONFIG_FRAME_POINTER, which: > > - creates simpler/faster function prologues and epilogues - no managing of RBP > needed > > - gives one more generic purpose register to work from. This matters less on > 64-bit kernels but it's a small effect. > > I've seen numbers of 1-2% of instruction count reduction in common kernel > workloads, which would be pretty significant on well cached workloads. thanks, -- js suse labs