* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > On Fri, 2010-10-15 at 04:50 +0200, Ingo Molnar wrote: > > * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > > From: Steven Rostedt <srostedt@xxxxxxxxxx> > > > > > > This patch adds the support for the C version of recordmcount and > > > compile times show ~ 12% improvement. > > > > I reported this recordmcount performance problem 2 years ago. Better > > later than never i guess. > > And I also remember saying after I posted this code that it would have > a compile time performance hit. Heck, it's a perl script running on > every object file. It was obvious what was at issue here. But it's > better to slow down the kernel build than to brick network cards. Well, it's even better to do neither! > Also, perl was much easier to do. Lets write the whole kernel in perl and forget about performance ;-) > That said, the embarrassing thing is not that I knew (or you reported > it) about this performance problem. I'm actually quite embarrassed > that I had this code sitting in my inbox for over a year. I just kept > having other things that were more important coming up than lowering > the compile time of the kernel. Although, I did work to get streamline > config to offset this performance hit. > > Finally, while at the End Users Summit, I decided to take a look at > John's code, and I was quite impressed. > > But as you said, better late than never. Yeah. Note that as a maintainer i need to grumble when i see some not-so-good event - even if there's a happy resolution! Otherwise such cases would tend to creep up in frequency ;-) > > > +ifdef CONFIG_DYNAMIC_FTRACE > > > + ifdef CONFIG_HAVE_C_MCOUNT_RECORD > > > + BUILD_C_RECORDMCOUNT := y > > > + export BUILD_C_RECORDMCOUNT > > > > > --- a/arch/x86/Kconfig > > > +++ b/arch/x86/Kconfig > > > @@ -33,6 +33,7 @@ config X86 > > > select HAVE_KRETPROBES > > > select HAVE_OPTPROBES > > > select HAVE_FTRACE_MCOUNT_RECORD > > > + select HAVE_C_MCOUNT_RECORD > > > > The naming is inconsistent here - it should be HAVE_C_RECORDMCOUNT, like > > the build variable has, and like the utility is called. If we are going > > to add this flag to most architectures we should name it consistently. > > Sure, want me to rebase it or just write a patch on top of it? Sure, patch on top would be fine. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
