From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3620115-1526026812-2-78538892584164130 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-charsets: X-Resolved-to: linux@kroah.com X-Delivered-to: linux@kroah.com X-Mail-from: linux-arch-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=fm2; t= 1526026812; b=LnrGnkQaD1FeZArek522swWtmzlV/0wP2d5eT9v2YQAID1F8rc FHYhDLnV1jHkKKZRDztxuzqeI35YG5h1UzFeuctJcJqUxmcyIWd13qAm3kt9LCqi XEn5XYKOFwKgV5Y17SezjE3Ky9B8xJzsfohYY+8WBthqsfgFDHFRZBOyBr19qZzy HnisjGiuQs2vmEivTJCB/OU6WIU9H5l7TaiE1J84T0fg3SWTxB3SYFz7A2Glj3Bl VHVT26RMLrgC6/Ed+3nfT5jOUl1Y0p2bPuV6IUXspJYrr/zX8STmuLWSnzsAzvHg 1WTumaC0D6+hkQWb9cEzbpdja3z+EwKBpnVw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id:sender :list-id; s=fm2; t=1526026812; bh=Qa7FkYz6Mou702Hgjy3L7SZWjDCZ56 i+V0mVw2Aarb8=; b=Hfwffwy/d1uSYfXPrt3iJjUgMzmob5gP5fxkoXvRPNlm4/ QQ7N8wtSdesvdV3fhVbhXXb4GMhvTSaKRdu93VIZVA9veH3ZxXcAbzXuTIFJ3sIT ppiUi3KHPgOxAa8dibEt19UJCSperg1BmMLbY84tyDSbEkiBEB2mazhc3G9LDZ7P SzuJWgnky/LrymQB+VlzgbtrPYr+p10mtlYKZG4i+vOJdbXlWdp+pFU26SrhEb9w HnQQLji0Y/3p6RqwKddMZIMwA82LSba6lPhwBVQU/hxnQfU0YWWfoMGZJQrujOVG 7rdPutnFduV/3z8ryxcLGkc61jABMDA1KYYCVJHg== ARC-Authentication-Results: i=1; mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=intel.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-arch-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=intel.com header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 Authentication-Results: mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=intel.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-arch-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=intel.com header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfK/uaE+NtiMgqALLPJoy4rL0s+lykFhTArShvmoH8s4zeOnYzDuQlbNfzOQ0iJpzCH524naGHZlMFBuVxOlszCQ7K8h4ESNEbGJsx5gmhdQ+DKaIzFZA m3hFxkd5Y4ULSWCBYCjpa40naEC9uAUMmt/nCKwHZx4ZpGppJ8EdW614r1uYPDx9oCp2Hb6zhvPgBHTQTs+v9kOh2FlU/T67mDYWhsD8Lkx/omN32l7vvB4b X-CM-Analysis: v=2.3 cv=FKU1Odgs c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=VUJBJC2UJ8kA:10 a=QyXUC8HyAAAA:8 a=D19gQVrFAAAA:8 a=6LfA-sCeOnnXfaMpjo4A:9 a=W4TVW4IDbPiebHqcZpNg:22 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752227AbeEKIUK (ORCPT ); Fri, 11 May 2018 04:20:10 -0400 Received: from mga09.intel.com ([134.134.136.24]:8561 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750852AbeEKIUJ (ORCPT ); Fri, 11 May 2018 04:20:09 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.49,387,1520924400"; d="scan'208";a="55002580" From: changbin.du@intel.com To: yamada.masahiro@socionext.com, michal.lkml@markovi.net, tglx@linutronix.de, mingo@redhat.com, akpm@linux-foundation.org Cc: rostedt@goodmis.org, rdunlap@infradead.org, x86@kernel.org, lgirdwood@gmail.com, broonie@kernel.org, arnd@arndb.de, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Changbin Du Subject: [PATCH v5 0/4] kernel hacking: GCC optimization for better debug experience (-Og) Date: Fri, 11 May 2018 16:09:43 +0800 Message-Id: <1526026187-11782-1-git-send-email-changbin.du@intel.com> X-Mailer: git-send-email 2.7.4 Sender: linux-arch-owner@vger.kernel.org X-Mailing-List: linux-arch@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Changbin Du Hi all, I know some kernel developers was searching for a method to dissable GCC optimizations, probably they want to apply GCC '-O0' option. But since Linux kernel replys on GCC optimization to remove some dead code, so '-O0' just breaks the build. They do need this because they want to debug kernel with qemu, simics, kgtp or kgdb. Thanks for the GCC '-Og' optimization level introduced in GCC 4.8, which offers a reasonable level of optimization while maintaining fast compilation and a good debugging experience. It is similar to '-O1' while perferring to keep debug ability over runtime speed. With '-Og', we can build a kernel with better debug ability and little performance drop after some simple change. In this series, firstly introduce a new config CONFIG_NO_AUTO_INLINE after two fixes for this new option. With this option, only functions explicitly marked with "inline" will be inlined. This will allow the function tracer to trace more functions because it only traces functions that the compiler has not inlined. Then introduce new config CC_OPTIMIZE_FOR_DEBUGGING which apply '-Og' optimization level for whole kernel, with a simple fix in fix_to_virt(). Currently I have only tested this option on x86 and ARM platform. Other platforms should also work but probably need some compiling fixes as what having done in this series. I leave that to who want to try this debug option. Comparison of vmlinux size: a bit smaller. w/o CONFIG_CC_OPTIMIZE_FOR_DEBUGGING $ size vmlinux text data bss dec hex filename 22665554 9709674 2920908 35296136 21a9388 vmlinux w/ CONFIG_CC_OPTIMIZE_FOR_DEBUGGING $ size vmlinux text data bss dec hex filename 21499032 10102758 2920908 34522698 20ec64a vmlinux Comparison of system performance: a bit drop (~6%). This benchmark of kernel compilation is suggested by Ingo Molnar. https://lkml.org/lkml/2018/5/2/74 Preparation: Set cpufreq to 'performance'. for ((cpu=0; cpu<120; cpu++)); do G=/sys/devices/system/cpu/cpu$cpu/cpufreq/scaling_governor [ -f $G ] && echo performance > $G done w/o CONFIG_CC_OPTIMIZE_FOR_DEBUGGING $ perf stat --repeat 5 --null --pre '\ cp -a kernel ../kernel.copy.$(date +%s); \ rm -rf *; \ git checkout .; \ echo 1 > /proc/sys/vm/drop_caches; \ find ../kernel* -type f | xargs cat >/dev/null; \ make -j kernel >/dev/null; \ make clean >/dev/null 2>&1; \ sync '\ \ make -j8 >/dev/null Performance counter stats for 'make -j8' (5 runs): 219.764246652 seconds time elapsed ( +- 0.78% ) w/ CONFIG_CC_OPTIMIZE_FOR_DEBUGGING $ perf stat --repeat 5 --null --pre '\ cp -a kernel ../kernel.copy.$(date +%s); \ rm -rf *; \ git checkout .; \ echo 1 > /proc/sys/vm/drop_caches; \ find ../kernel* -type f | xargs cat >/dev/null; \ make -j kernel >/dev/null; \ make clean >/dev/null 2>&1; \ sync '\ \ make -j8 >/dev/null Performance counter stats for 'make -j8' (5 runs): 233.574187771 seconds time elapsed ( +- 0.19% ) v5: o Exchange the position of last two patches to avoid compiling error. v4: o Remove aready merged one "regulator: add dummy function of_find_regulator_by_node". Changbin Du (4): x86/mm: surround level4_kernel_pgt with #ifdef CONFIG_X86_5LEVEL...#endif kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations ARM: mm: fix build error in fix_to_virt with CONFIG_CC_OPTIMIZE_FOR_DEBUGGING kernel hacking: new config CC_OPTIMIZE_FOR_DEBUGGING to apply GCC -Og optimization Makefile | 10 ++++++++++ arch/arm/mm/mmu.c | 2 +- arch/x86/include/asm/pgtable_64.h | 2 ++ arch/x86/kernel/head64.c | 13 ++++++------- include/linux/compiler-gcc.h | 2 +- include/linux/compiler.h | 2 +- init/Kconfig | 19 +++++++++++++++++++ lib/Kconfig.debug | 17 +++++++++++++++++ 8 files changed, 57 insertions(+), 10 deletions(-) -- 2.7.4