Messages in this thread | | | Date | Mon, 29 Nov 2010 16:52:50 +0800 | From | Américo Wang <> | Subject | Re: [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 <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?
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 http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |