Messages in this thread | | | From | Hui Zhu <> | Date | Mon, 29 Nov 2010 17:11:23 +0800 | Subject | Re: [PATCH] Built kernel without -O2 option |
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On Mon, Nov 29, 2010 at 16:52, Américo Wang <xiyou.wangcong@gmail.com> wrote: > On Mon, Nov 29, 2010 at 04:24:42PM +0800, Hui Zhu wrote: >>On Mon, Nov 29, 2010 at 16:16, Américo Wang <xiyou.wangcong@gmail.com> 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 big one is: >>>>(gdb) p ret >>>>$3 = <value optimized out> >>>>And the code execution order is not right. >>>> >>>>This is becuase the Kernel is bult with gcc -O2. Gcc 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". It will make kernel be built without -O2. >>>> >>>>I built and use it in i386 and x86_64. I will try to make it OK in other 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 them to O2. >>Actually, this is the main work, find out the file that need the O2. :) >> >>For example: >>ifdef CONFIG_CC_CLOSE_OPTIMIZATION >>CFLAGS_fpu.o += -O2 >>CFLAGS_aesni-intel_glue.o += -O2 >>CFLAGS_ghash-clmulni-intel_glue.o += -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(). > > I think it is not alone. :) > > Also, since many inline functions sit in hot-path, are there any > performance regressions with your patch applied? >
I did some nm, looks each file that have inline have a special code for inline function.
> BTW, you need to Cc kbuild for makefile changes like this. >
Thanks for you remind me.
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