On Thu, 8 Dec 2016, Josh Poimboeuf wrote: > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 215612c..b4a6663 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -155,6 +155,7 @@ config X86 > select HAVE_PERF_REGS > select HAVE_PERF_USER_STACK_DUMP > select HAVE_REGS_AND_STACK_ACCESS_API > + select HAVE_RELIABLE_STACKTRACE if X86_64 && FRAME_POINTER && > STACK_VALIDATION
Tests to measure possible performance penalty of frame pointers were done by Mel Gorman. The outcome was quite clear. There IS a measurable impact. The percentage depends on the workflow but I think it is safe to say that FP usually takes 5-10 percents. If my understanding is correct there is no single culprit. Register pressure is definitely not a problem. We ran simple benchmarks while taking a register away from GCC (RBP or a common one). The impact is a combination of more cacheline pressure, more memory accesses and the fact that the kernel contains a lot of small functions. Thus, I think that DWARF should be the way to go here. Other than that the patch looks good to me. Miroslav
