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 X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60E92C5ACCC for ; Thu, 18 Oct 2018 16:26:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F25E221476 for ; Thu, 18 Oct 2018 16:26:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="e6ffNfOJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F25E221476 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728301AbeJSA16 (ORCPT ); Thu, 18 Oct 2018 20:27:58 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:36998 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727402AbeJSA16 (ORCPT ); Thu, 18 Oct 2018 20:27:58 -0400 Received: by mail-pf1-f195.google.com with SMTP id j23-v6so15118314pfi.4; Thu, 18 Oct 2018 09:26:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=eswFvXY3QOXKeqz4iX0KykGT9Z/UnnIsiENX5EkGwfM=; b=e6ffNfOJp6ZDpEVjOd3pQmo9VP3kQcduFMURH5eeBPw5y/cCOANG/A65+Yc2jIUewE Gs4kl8TJA7lPCu2S41sk5a4W+DRUUITwx9FnlnwzVvIf2VE7Y0x+u+CluZCg4ccO1idK dwa+ygs2Q2WYzZJcnymmY5uEnivmjYAKzsx7fjT66Fyng5WLKzK7qrj7kWhJsK/9lgH7 6K/pf+n2SATxkmXtJwAXPcJiTJyYGErtui79NHGtVuSnIUHzIqy1sW3oClKZslqY2Izk JRfNnl5KtvGsBWoYm4ASliEiUWbbLD4ESv8cV9VwFoeX1UQSsv3V6YH4OezNUtw2W00c mp0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=eswFvXY3QOXKeqz4iX0KykGT9Z/UnnIsiENX5EkGwfM=; b=nNKvQgn+xUqRdjM/M3k+aZRl5msO5Wf+n6t0Y0RaZPgQRJf3jyGP5c2ecQ/2BDgmki sm1e0l19Kn3J7/Ou4PTiSUdVy3xHVqUQOuf6q8UaiBAUMrDgkf/pV6qpPsSBzpir9vDY 9dL3r47+6sWpxkdxjuHFTGawc9owChQHAsaHpHav9yUPdeXr3M1eJqs5wRzCKDGS/nE4 gaTgUmiAFykqU3KUChSeZJntcmAMjm8YB+ZoaXY8lwZDEZPoO5oSPST9MiUWHfJb3a05 KUBRBJgt1KHlj/YEfHvc6oO/4zGLQXkeDDIqAne+3F3d7ck7vcl7VNQoGv1iIzFsYQ39 eBAg== X-Gm-Message-State: ABuFfogxytPXyeQeulIJClKRbbvv5d7d80qJ4u2fMa5vExYFfyX2mpnw Ed4787pagzapnYB1Gg+rpx0= X-Google-Smtp-Source: ACcGV63syWZzXMDeAgJBNjDc4ndj4WaPZqRWg1wPhylWtMU/lJ0xR38gkidKMTIYM5YvDPhDVqnKyA== X-Received: by 2002:a63:6946:: with SMTP id e67-v6mr28935736pgc.119.1539879973377; Thu, 18 Oct 2018 09:26:13 -0700 (PDT) Received: from vultr.guest ([2001:19f0:6001:4ff6:5400:1ff:feb7:a195]) by smtp.gmail.com with ESMTPSA id 5-v6sm27813420pgt.83.2018.10.18.09.26.12 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Oct 2018 09:26:12 -0700 (PDT) From: Du Changbin To: yamada.masahiro@socionext.com, michal.lkml@markovi.net, tglx@linutronix.de, mingo@redhat.com, linux@armlinux.org.uk, akpm@linux-foundation.org Cc: rostedt@goodmis.org, x86@kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sparse@vger.kernel.org, Du Changbin Subject: [PATCH 0/4] kernel hacking: GCC optimization for better debug experience (-Og) Date: Thu, 18 Oct 2018 16:25:44 +0000 Message-Id: <20181018162548.6399-1-changbin.du@gmail.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, I have posted this series several months ago but interrupted by personal affairs. Now I get time to complete this task. Thanks for all of the reviewers. 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% ) 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 | 11 +++++++++++ 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 | 25 +++++++++++++++++++++++++ 8 files changed, 66 insertions(+), 10 deletions(-) -- 2.17.1