From patchwork Sat Feb 8 23:05:03 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andi Kleen X-Patchwork-Id: 3611561 Return-Path: X-Original-To: patchwork-linux-kbuild@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 7F04A9F392 for ; Sat, 8 Feb 2014 23:05:57 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id AA02E2018B for ; Sat, 8 Feb 2014 23:05:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D2C120181 for ; Sat, 8 Feb 2014 23:05:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751192AbaBHXFy (ORCPT ); Sat, 8 Feb 2014 18:05:54 -0500 Received: from mga01.intel.com ([192.55.52.88]:8397 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751224AbaBHXFy (ORCPT ); Sat, 8 Feb 2014 18:05:54 -0500 Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP; 08 Feb 2014 15:05:53 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,808,1384329600"; d="scan'208";a="471946178" Received: from laut.jf.intel.com (HELO localhost) ([10.23.232.94]) by fmsmga001.fm.intel.com with ESMTP; 08 Feb 2014 15:05:51 -0800 Received: by localhost (Postfix, from userid 1000) id CBF65124ACD; Sun, 9 Feb 2014 00:05:11 +0100 (CET) From: Andi Kleen To: linux-kernel@vger.kernel.org Cc: mmarek@suse.cz, linux-kbuild@vger.kernel.org, torvalds@linux-foundation.org, Andi Kleen Subject: [PATCH] kbuild: Support split debug info Date: Sun, 9 Feb 2014 00:05:03 +0100 Message-Id: <1391900703-18163-1-git-send-email-ak@linux.intel.com> X-Mailer: git-send-email 1.8.5.2 Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This is an alternative approach to lower the overhead of debug info (as we discussed a few days ago) gcc 4.7+ and newer binutils have a new "split debug info" debug info model where the debug info is only written once into central ".dwo" files. This avoids having to copy it around multiple times, from the object files to the final executable. It also lowers the disk space requirement. In addition it defaults to compressed debug data. More details here: http://gcc.gnu.org/wiki/DebugFission This patch adds a new option to enable it. It has to be an option, because it'll undoubtedly break everyone's debuginfo packaging scheme. gdb/objdump/etc. all still work, if you have new enough versions. I don't see big compile wins (maybe a second or two faster or so), but the object dirs with debuginfo get significantly smaller. My standard kernel config (slightly bigger than defconfig) goes from 2.9G disk space to 1.1G objdir (without debuginfo reduced). I presume if you are IO limited it will also compile faster. Only problem I've seen so far is that it doesn't play well with ccache. Signed-off-by: Andi Kleen --- Makefile | 6 ++++++ lib/Kconfig.debug | 13 +++++++++++++ 2 files changed, 19 insertions(+) diff --git a/Makefile b/Makefile index 606ef7c..2f3d9d1 100644 --- a/Makefile +++ b/Makefile @@ -638,7 +638,11 @@ endif endif ifdef CONFIG_DEBUG_INFO +ifdef CONFIG_DEBUG_INFO_SPLIT +KBUILD_CFLAGS += $(call cc-option, -gsplit-dwarf, -g) +else KBUILD_CFLAGS += -g +endif KBUILD_AFLAGS += -Wa,--gdwarf-2 endif @@ -1072,6 +1076,8 @@ MRPROPER_FILES += .config .config.old .version .old_version $(version_h) \ extra_certificates signing_key.x509.keyid \ signing_key.x509.signer +CLEAN_FILES += .*.dwo + # clean - Delete most, but leave enough to build external modules # clean: rm-dirs := $(CLEAN_DIRS) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index a48abea..367a6ba 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -143,6 +143,19 @@ config DEBUG_INFO_REDUCED DEBUG_INFO build and compile times are reduced too. Only works with newer gcc versions. +config DEBUG_INFO_SPLIT + bool "Produce split debuginfo in .dwo files" + depends on DEBUG_INFO + help + Generate debug info into separate .dwo files. This can be + faster for building than including the debug information directly + in the object files and the vmlinux, as it only needs to + be stored once to disk, not multiple times in object files. + Requires recent gcc (4.8+) and recent gdb/binutils. + Any tool that packages or reads debug information would need + to know about the .dwo files and include them. + Currently incompatible with ccache. + config ENABLE_WARN_DEPRECATED bool "Enable __deprecated logic" default y