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| author | Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> | 2014-06-25 08:49:03 -0700 |
|---|---|---|
| committer | Jiri Olsa <jolsa@kernel.org> | 2014-06-27 11:14:51 +0200 |
| commit | a60335ba32981db5bc057b35782644e9e2436407 (patch) | |
| tree | e6d63c2427f4c15a628cbbfd955d1b9b91c22704 /tools/perf/util/machine.c | |
| parent | 21da83fb6c3ff67e969b8770bbb33138c9ede88e (diff) | |
| download | blackbird-op-linux-a60335ba32981db5bc057b35782644e9e2436407.tar.gz blackbird-op-linux-a60335ba32981db5bc057b35782644e9e2436407.zip | |
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 <maynard@us.ibm.com>
Tested-by: Maynard Johnson <maynard@us.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20140625154903.GA29607@us.ibm.com
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Diffstat (limited to 'tools/perf/util/machine.c')
| -rw-r--r-- | tools/perf/util/machine.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index c73e1fc12e53..e9b943acaa5e 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1281,7 +1281,9 @@ static int machine__resolve_callchain_sample(struct machine *machine, u8 cpumode = PERF_RECORD_MISC_USER; int chain_nr = min(max_stack, (int)chain->nr); int i; + int j; int err; + int skip_idx __maybe_unused; callchain_cursor_reset(&callchain_cursor); @@ -1290,14 +1292,26 @@ static int machine__resolve_callchain_sample(struct machine *machine, return 0; } + /* + * Based on DWARF debug information, some architectures skip + * a callchain entry saved by the kernel. + */ + skip_idx = arch_skip_callchain_idx(machine, thread, chain); + for (i = 0; i < chain_nr; i++) { u64 ip; struct addr_location al; if (callchain_param.order == ORDER_CALLEE) - ip = chain->ips[i]; + j = i; else - ip = chain->ips[chain->nr - i - 1]; + j = chain->nr - i - 1; + +#ifdef HAVE_SKIP_CALLCHAIN_IDX + if (j == skip_idx) + continue; +#endif + ip = chain->ips[j]; if (ip >= PERF_CONTEXT_MAX) { switch (ip) { |
