Re: [PATCH v3 01/15] stacktrace/x86: add function for detecting reliable stack traces
From: Miroslav Benes <mbenes@suse.cz>
Date: 2016-12-19 16:25:25
Also in:
linux-s390, lkml
On Thu, 8 Dec 2016, Josh Poimboeuf wrote:
quoted hunk ↗ jump to hunk
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