From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 11818 invoked by alias); 29 Nov 2010 20:51:59 -0000 Received: (qmail 11809 invoked by uid 22791); 29 Nov 2010 20:51:58 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,TW_CL,TW_KG X-Spam-Check-By: sourceware.org Received: from mail-yw0-f41.google.com (HELO mail-yw0-f41.google.com) (209.85.213.41) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 29 Nov 2010 20:51:50 +0000 Received: by ywg4 with SMTP id 4so56957ywg.0 for ; Mon, 29 Nov 2010 12:51:49 -0800 (PST) MIME-Version: 1.0 Received: by 10.151.82.14 with SMTP id j14mr67194ybl.115.1291063909300; Mon, 29 Nov 2010 12:51:49 -0800 (PST) Received: by 10.151.27.17 with HTTP; Mon, 29 Nov 2010 12:51:49 -0800 (PST) In-Reply-To: <20101129085250.GF5218@cr0.nay.redhat.com> References: <20101129081619.GD5218@cr0.nay.redhat.com> <20101129085250.GF5218@cr0.nay.redhat.com> Date: Mon, 29 Nov 2010 20:51:00 -0000 Message-ID: Subject: Re: [PATCH] Built kernel without -O2 option From: richard -rw- weinberger To: =?ISO-8859-1?Q?Am=E9rico_Wang?= Cc: Hui Zhu , linux-kernel@vger.kernel.org, gdb@sourceware.org, hellogcc@freelists.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org X-SW-Source: 2010-11/txt/msg00128.txt.bz2 On Mon, Nov 29, 2010 at 9:52 AM, Am=E9rico Wang = wrote: > On Mon, Nov 29, 2010 at 04:24:42PM +0800, Hui Zhu wrote: >>On Mon, Nov 29, 2010 at 16:16, Am=E9rico Wang = wrote: >>> On Mon, Nov 29, 2010 at 11:56:15AM +0800, Hui Zhu wrote: >>>>Hi, >>>> >>>>Now, there are a lot of ways to debug the Linux kernel with GDB, like >>>>qemu, kgtp or kgdb and so on. >>>>But the developer more like add a printk. It have a lot of reason, a bi= g one is: >>>>(gdb) p ret >>>>$3 =3D >>>>And the code execution order is not right. >>>> >>>>This is becuase the Kernel is bult with gcc -O2. =A0Gcc will not >>>>generate enough debug message with file with -O2. >>>>So GDB cannot work very well with Linux kernel. >>>> >>>>So I make a patch that add a option in "Kernel hacking" called "Close >>>>GCC optimization". =A0It will make kernel be built without -O2. >>>> >>>>I built and use it in i386 and x86_64. =A0I will try to make it OK in o= ther arch. >>>> >>> >>> The problem is that some functions _have to_ be inlined and gcc without= -O2 >>> doesn't inline them. Have check all the cases? I doubt. >> >>If they really need O2, I set =A0them to O2. >>Actually, this is the main work, find out the file that need the O2. =A0:) >> >>For example: >>ifdef CONFIG_CC_CLOSE_OPTIMIZATION >>CFLAGS_fpu.o =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 +=3D -O2 >>CFLAGS_aesni-intel_glue.o =A0 =A0 =A0 =A0 =A0 =A0 =A0+=3D -O2 >>CFLAGS_ghash-clmulni-intel_glue.o =A0 =A0 =A0+=3D -O2 >>endif > > No, I didn't mean this, I meant some function that have to be inlined > are those who only work when being inlined, e.g. current_text_addr(). Can you please explain to me why some functions work only when they are inl= ined? Is it because of asm() black magic? > I think it is not alone. :) > > Also, since many inline functions sit in hot-path, are there any > performance regressions with your patch applied? > > BTW, you need to Cc kbuild for makefile changes like this. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > Please read the FAQ at =A0http://www.tux.org/lkml/ > --=20 Thanks, //richard