From patchwork Tue Jul 15 23:16:11 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andi Kleen X-Patchwork-Id: 4561951 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 2F3039F37C for ; Tue, 15 Jul 2014 23:17:28 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3AF832017E for ; Tue, 15 Jul 2014 23:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE66B20123 for ; Tue, 15 Jul 2014 23:17:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755622AbaGOXRZ (ORCPT ); Tue, 15 Jul 2014 19:17:25 -0400 Received: from mga11.intel.com ([192.55.52.93]:35966 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759407AbaGOXRL (ORCPT ); Tue, 15 Jul 2014 19:17:11 -0400 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga102.fm.intel.com with ESMTP; 15 Jul 2014 16:17:08 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,668,1400050800"; d="scan'208";a="570380384" Received: from laut.jf.intel.com (HELO localhost) ([10.23.232.55]) by fmsmga002.fm.intel.com with ESMTP; 15 Jul 2014 16:17:07 -0700 Received: by localhost (Postfix, from userid 1000) id CBB78124B07; Wed, 16 Jul 2014 01:16:19 +0200 (CEST) From: Andi Kleen To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andi Kleen , Dirk Gouders , mmarek@suse.cz Subject: [PATCH 1/2] kbuild: Support split debug info v3 Date: Wed, 16 Jul 2014 01:16:11 +0200 Message-Id: <1405466172-17055-1-git-send-email-andi@firstfloor.org> 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=-6.9 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 From: Andi Kleen 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 requirements. 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) shrinks from 2.9G disk space to 1.1G objdir (with non reduced debuginfo). I presume if you are IO limited the compile time difference will be larger. Only problem I've seen so far is that it doesn't play well with older versions of ccache (apparently fixed, see https://bugzilla.samba.org/show_bug.cgi?id=10005) v2: various fixes from Dirk Gouders. Improve commit message slightly. v3: Fix clean rules and improve Kconfig slightly Cc: Dirk Gouders Cc: mmarek@suse.cz Signed-off-by: Andi Kleen --- .gitignore | 1 + Makefile | 5 +++++ lib/Kconfig.debug | 13 +++++++++++++ 3 files changed, 19 insertions(+) diff --git a/.gitignore b/.gitignore index f4c0b09..e213b27 100644 --- a/.gitignore +++ b/.gitignore @@ -34,6 +34,7 @@ *.gcno modules.builtin Module.symvers +*.dwo # # Top-level generic files diff --git a/Makefile b/Makefile index 1317563..953659e 100644 --- a/Makefile +++ b/Makefile @@ -683,9 +683,13 @@ endif endif ifdef CONFIG_DEBUG_INFO +ifdef CONFIG_DEBUG_INFO_SPLIT +KBUILD_CFLAGS += $(call cc-option, -gsplit-dwarf, -g) +else KBUILD_CFLAGS += -g KBUILD_AFLAGS += -Wa,-gdwarf-2 endif +endif ifdef CONFIG_DEBUG_INFO_REDUCED KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ @@ -1371,6 +1375,7 @@ clean: $(clean-dirs) @find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \ \( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \ -o -name '*.ko.*' \ + -o -name '*.dwo' \ -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \ -o -name '*.symtypes' -o -name 'modules.order' \ -o -name modules.builtin -o -name '.tmp_*.o.*' \ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 7a638aa..fb07c33 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 (4.7+) and recent gdb/binutils. + Any tool that packages or reads debug information would need + to know about the .dwo files and include them. + Incompatible with older versions of ccache. + config ENABLE_WARN_DEPRECATED bool "Enable __deprecated logic" default y