From a60335ba32981db5bc057b35782644e9e2436407 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Wed, 25 Jun 2014 08:49:03 -0700 Subject: perf tools powerpc: Adjust callchain based on DWARF debug info When saving the callchain on Power, the kernel conservatively saves excess entries in the callchain. A few of these entries are needed in some cases but not others. We should use the DWARF debug information to determine when the entries are needed. Eg: the value in the link register (LR) is needed only when it holds the return address of a function. At other times it must be ignored. If the unnecessary entries are not ignored, we end up with duplicate arcs in the call-graphs. Use the DWARF debug information to determine if any callchain entries should be ignored when building call-graphs. Callgraph before the patch: 14.67% 2234 sprintft libc-2.18.so [.] __random | --- __random | |--61.12%-- __random | | | |--97.15%-- rand | | do_my_sprintf | | main | | generic_start_main.isra.0 | | __libc_start_main | | 0x0 | | | --2.85%-- do_my_sprintf | main | generic_start_main.isra.0 | __libc_start_main | 0x0 | --38.88%-- rand | |--94.01%-- rand | do_my_sprintf | main | generic_start_main.isra.0 | __libc_start_main | 0x0 | --5.99%-- do_my_sprintf main generic_start_main.isra.0 __libc_start_main 0x0 Callgraph after the patch: 14.67% 2234 sprintft libc-2.18.so [.] __random | --- __random | |--95.93%-- rand | do_my_sprintf | main | generic_start_main.isra.0 | __libc_start_main | 0x0 | --4.07%-- do_my_sprintf main generic_start_main.isra.0 __libc_start_main 0x0 TODO: For split-debug info objects like glibc, we can only determine the call-frame-address only when both .eh_frame and .debug_info sections are available. We should be able to determin the CFA even without the .eh_frame section. Fix suggested by Anton Blanchard. Thanks to valuable input on DWARF debug information from Ulrich Weigand. Reported-by: Maynard Johnson Tested-by: Maynard Johnson Signed-off-by: Sukadev Bhattiprolu Link: http://lkml.kernel.org/r/20140625154903.GA29607@us.ibm.com Signed-off-by: Jiri Olsa --- tools/perf/config/Makefile | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'tools/perf/config') diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile index f30ac5e..346bdb6 100644 --- a/tools/perf/config/Makefile +++ b/tools/perf/config/Makefile @@ -48,6 +48,10 @@ ifneq ($(ARCH),$(filter $(ARCH),x86 arm)) NO_LIBDW_DWARF_UNWIND := 1 endif +ifeq ($(ARCH),powerpc) + CFLAGS += -DHAVE_SKIP_CALLCHAIN_IDX +endif + ifeq ($(LIBUNWIND_LIBS),) NO_LIBUNWIND := 1 else -- cgit v1.1