Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754273AbbFRKdO (ORCPT ); Thu, 18 Jun 2015 06:33:14 -0400 Received: from us01smtprelay-2.synopsys.com ([198.182.60.111]:42285 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752968AbbFRKdF (ORCPT ); Thu, 18 Jun 2015 06:33:05 -0400 Message-ID: <55829E51.3060007@synopsys.com> Date: Thu, 18 Jun 2015 16:02:49 +0530 From: Vineet Gupta User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel.cross-arch,gmane.linux.kernel To: Michal Marek , Geert Uytterhoeven CC: "linux-arch@vger.kernel.org" , lkml Subject: Re: subtle side effect of commit a1c48bb160f836 References: <55826966.6050202@synopsys.com> <20150618081329.GA9434@pobox.suse.cz> <55828527.8050901@synopsys.com> <55829A0B.8070804@suse.cz> In-Reply-To: <55829A0B.8070804@suse.cz> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.3] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3062 Lines: 71 On Thursday 18 June 2015 03:44 PM, Michal Marek wrote: > Dne 18.6.2015 v 10:45 Vineet Gupta napsal(a): >> > On Thursday 18 June 2015 01:43 PM, Michal Marek wrote: >>>>> >>>> Alternatively, as we already have CONFIG_CC_OPTIMIZE_FOR_SIZE, >>>>> >>>> a(nother) Kconfig option may make sense. >>> >> We can also introduce some ARCH_CFLAGS that is appended near the end of >>> >> the list, and have arc/Makefile add its -O3 there. But I'd like to why >>> >> the -O3 needs to be there in first place. >> > >> > This is how historically ARC kernels have been built. We do track performance >> > results LMBench/hackbench... and going from -O3 to -O2 caused a sudden dip in some >> > of the numbers when we measured 3.18 (vs. 3.13) >> > >>> >> Obviously, the kernel works >>> >> with -O2, otherwise the regression would have been identified earlier. >> > >> > Its a performance thing - so yeah -O2 works, but -O3 works even better :-) >> > >>> >> So why can't users specify -O3 in KCFLAGS like on any other >>> >> architecture. >> > >> > Sweet, I didn't know about this. But I don't see any arch setting this - only tile >> > using it. So yeah - below does the trick ! >> > >> > ---------> >> > From 5e44cd2ed69b1d030b4cb87600d2767b69c35537 Mon Sep 17 00:00:00 2001 >> > From: Vineet Gupta >> > Date: Thu, 18 Jun 2015 13:54:01 +0530 >> > Subject: [PATCH] ARC: Override toplevel default -O2 with -O3 >> > >> > ARC kernels have historically been built with -O3, despite top level >> > Makefile defaulting to -O2. This was facilitated by implicitly ordering >> > of arch makefile include AFTER top level assigned -O2. >> > >> > An upstream fix to top level a1c48bb160f ("Makefile: Fix unrecognized >> > cross-compiler command line options") changed the ordering, making ARC >> > -O3 defunt. >> > >> > Fix that by NOT relying on any ordering whatsoever and use the right >> > mechanism to do the over-rides. >> > >> > Suggested-by: Michal Marek >> > Cc: Geert Uytterhoeven >> > Cc: >> > Signed-off-by: Vineet Gupta >> > --- >> > arch/arc/Makefile | 1 + >> > 1 file changed, 1 insertion(+) >> > >> > diff --git a/arch/arc/Makefile b/arch/arc/Makefile >> > index 86c71b2089d2..c23f3f2b0ff8 100644 >> > --- a/arch/arc/Makefile >> > +++ b/arch/arc/Makefile >> > @@ -44,6 +44,7 @@ endif >> > ifndef CONFIG_CC_OPTIMIZE_FOR_SIZE >> > # Generic build system uses -O2, we want -O3 >> > cflags-y += -O3 >> > +KCFLAGS += -O3 >> > endif > Uh, this is not what I meant. KCFLAGS is a *user* setting. It's meant to > be set in the environment or command line. Well I don't want to rely on external settings whatsoever to enforce this. If this is not the right way, what do u suggest I do to help fix this. -Vineet -- 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/