Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760006Ab0FKAwz (ORCPT ); Thu, 10 Jun 2010 20:52:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19041 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754423Ab0FKAwx (ORCPT ); Thu, 10 Jun 2010 20:52:53 -0400 Date: Thu, 10 Jun 2010 20:52:07 -0400 From: Jason Baron To: Mathieu Desnoyers Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de, rostedt@goodmis.org, andi@firstfloor.org, roland@redhat.com, rth@redhat.com, mhiramat@redhat.com, fweisbec@gmail.com, avi@redhat.com, davem@davemloft.net, vgoyal@redhat.com, sam@ravnborg.org Subject: Re: [PATCH 03/13] jump label v9: x86 support Message-ID: <20100611005206.GA2379@redhat.com> References: <1276171930.2077.200.camel@twins> <20100610121440.GA20130@elte.hu> <20100610150422.GA3923@redhat.com> <20100610161339.GA20448@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100610161339.GA20448@Krystal> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1648 Lines: 49 On Thu, Jun 10, 2010 at 12:13:39PM -0400, Mathieu Desnoyers wrote: > * Jason Baron (jbaron@redhat.com) wrote: > > On Thu, Jun 10, 2010 at 02:14:40PM +0200, Ingo Molnar wrote: > > > * Peter Zijlstra wrote: > > > > > > > On Wed, 2010-06-09 at 17:39 -0400, Jason Baron wrote: > > > > > + select HAVE_ARCH_JUMP_LABEL if !CC_OPTIMIZE_FOR_SIZE > > > > > > > > That deserves a comment somewhere, it basically makes OPTIMIZE_FOR_SIZE > > > > useless... > > > > > > Hm, we need more than a comment for that - distros enable CC_OPTIMIZE_FOR_SIZE > > > all the time, for the massive kernel image (and hotpath cache footprint) > > > savings. Is this fixable? > > > > > > Thanks, > > > > > > Ingo > > > > > > > When I tested 'jump label' with CC_OPTIMIZE_FOR_SIZE, I saw a small > > performance drop , b/c there is less block re-ordering happening. > > Is this a performance drop compared to a jump-label-less kernel or > compared to -O2 kernel compiled with jump labels ? Or both ? > > Mathieu > Hi Mathieu, So I'm quoting tbench benchmark here. The performance drop was jump label vs. all jump label patches backed out on -Os. If we move to -02, both the no jump label patches and the jump label patches applied are faster than all jump label patches backed out on -Os. so: jump labels -02 > no jump labels -02 > no jump labels -0s > jump lables -Os thanks, -Jason -- 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/