[lkml]   [2010]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] Built kernel without -O2 option
On Mon, Nov 29, 2010 at 04:24:42PM +0800, Hui Zhu wrote:
>On Mon, Nov 29, 2010 at 16:16, Américo Wang <> wrote:
>> On Mon, Nov 29, 2010 at 11:56:15AM +0800, Hui Zhu wrote:
>>>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:
>CFLAGS_fpu.o += -O2
>CFLAGS_aesni-intel_glue.o += -O2
>CFLAGS_ghash-clmulni-intel_glue.o += -O2

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?

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
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2010-11-29 09:51    [W:0.085 / U:3.832 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site