From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3663AC433F5 for ; Mon, 25 Apr 2022 08:02:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234462AbiDYIE4 (ORCPT ); Mon, 25 Apr 2022 04:04:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231858AbiDYIEd (ORCPT ); Mon, 25 Apr 2022 04:04:33 -0400 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E7E7B1582E for ; Mon, 25 Apr 2022 01:01:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650873689; x=1682409689; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=/QcU6MWYTPWZ4Kj6gQUq7qXQoT/0fHP0aO/R9fTkgkM=; b=f2Kovs0+xiMAdXoeeTg2xYqIJujz6xbcIBg33eCw9Gy0WQaDVZDAcjk+ j/9E7T2MBRwAC+NfLilbCB8N12p0BDnp6Doksbpv8iGpK+6b+SF8jebRd BPqdPSaUGZeRnhrPt2RaN9HeNAc1i/9LcZEpz8sSw2TZPAqYqZZn4TJ+d CqWiPiFbsZtiDou/4ixfH1HmnMf7uTGyV1+FhPxIzJ0MIDjI5PYQhariH cfgvtkEMVclBSJbeL0h2+E6LHuEwKJnhYy+i12oWGnCHjY9D64QFMkxfc PmJC/Byk6JZwU0KlDVIfKuN1Zv1Lh3FTT9qbLsXfDS1lrXTYMSc/CD/kc g==; X-IronPort-AV: E=McAfee;i="6400,9594,10327"; a="351623413" X-IronPort-AV: E=Sophos;i="5.90,287,1643702400"; d="scan'208";a="351623413" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2022 01:01:29 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,287,1643702400"; d="scan'208";a="579155418" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.138]) by orsmga008.jf.intel.com with ESMTP; 25 Apr 2022 01:01:26 -0700 Date: Mon, 25 Apr 2022 16:01:26 +0800 From: Feng Tang To: Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Josh Poimboeuf , Denys Vlasenko Subject: Re: [PATCH v2] x86, vmlinux.lds: Add debug option to force all data sections aligned Message-ID: <20220425080126.GA33905@shbuild999.sh.intel.com> References: <20220424122533.27590-1-feng.tang@intel.com> <20220425075335.GZ2731@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220425075335.GZ2731@worktop.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On Mon, Apr 25, 2022 at 09:53:35AM +0200, Peter Zijlstra wrote: > On Sun, Apr 24, 2022 at 08:25:33PM +0800, Feng Tang wrote: > > > diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug > > index d3a6f74a94bd..7b8cfe9717f2 100644 > > --- a/arch/x86/Kconfig.debug > > +++ b/arch/x86/Kconfig.debug > > @@ -225,6 +225,19 @@ config PUNIT_ATOM_DEBUG > > The current power state can be read from > > /sys/kernel/debug/punit_atom/dev_power_state > > > > +config DEBUG_FORCE_DATA_SECTION_ALIGNED > > + bool "Force all data sections to be THREAD_SIZE aligned" > > s/THREAD_SIZE/PAGE_SIZE/ as that seems to be what the actual patch does. Thanks for the catch! It was changed from v1 to v2, I should reviewed these texts more carefully, and there is another similar typo in the commit log. > > + depends on EXPERT && !DYNAMIC_DEBUG > > + help > > + There are cases that a commit from one kernel domain changes > > + data sections' alignment of other domains, as they are all > > + linked together compactly, and cause magic performance bump > > + (regression or improvement), which is hard to debug. Enable > > + this option will help to verify if the bump is caused by > > + data alignment changes. > > + > > + It is mainly for debug and performance tuning use. > > + > > choice > > prompt "Choose kernel unwinder" > > default UNWINDER_ORC if X86_64 > > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > > index 7fda7f27e762..6add703de45f 100644 > > --- a/arch/x86/kernel/vmlinux.lds.S > > +++ b/arch/x86/kernel/vmlinux.lds.S > > @@ -155,7 +155,17 @@ SECTIONS > > X86_ALIGN_RODATA_END > > > > /* Data */ > > - .data : AT(ADDR(.data) - LOAD_OFFSET) { > > + .data : AT(ADDR(.data) - LOAD_OFFSET) > > +#ifdef CONFIG_DEBUG_FORCE_DATA_SECTION_ALIGNED > > + /* > > + * In theroy, THREAD_SIZE as the biggest alignment of below sections > > I think the more common spelling is: 'theory' :-) Yes, will change in the next verson. Thanks, Feng > > + * should be picked, but since upper 'X86_ALIGN_RODATA_END' can > > + * ganrantees the alignment of 'INIT_TASK_DATA', PAGE_SIZE is picked > > + * instead to reduce size of kernel binary > > + */ > > + SUBALIGN(PAGE_SIZE) > > +#endif > > + { > > /* Start of data section */ > > _sdata = .; > > > > -- > > 2.27.0 > >