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Subject[PATCH v4 06/15] perf report: fall-back to function name comparison for -g srcline
Date
When a callchain entry has no srcline available, we ended up
comparing the instruction pointer. I consider this to be not
too useful. Rather, I think we should group the entries by
function name, which this patch adds. For people who want to
split the data on the IP boundary, using `-g address` is the
correct choice.

Before:

~~~~~
100.00% 38.86% [.] main
|
|--61.14%--main inlining.cpp:14
| std::norm<double> complex:664
| std::_Norm_helper<true>::_S_do_it<double> complex:654
| std::abs<double> complex:597
| std::__complex_abs complex:589
| |
| |--56.03%--hypot
| | |
| | |--8.45%--__hypot_finite
| | |
| | |--7.62%--__hypot_finite
| | |
| | |--2.29%--__hypot_finite
| | |
| | |--2.24%--__hypot_finite
| | |
| | |--2.06%--__hypot_finite
| | |
| | |--1.81%--__hypot_finite
...
~~~~~

After:

~~~~~
100.00% 38.86% [.] main
|
|--61.14%--main inlining.cpp:14
| std::norm<double> complex:664
| std::_Norm_helper<true>::_S_do_it<double> complex:654
| std::abs<double> complex:597
| std::__complex_abs complex:589
| |
| |--60.29%--hypot
| | |
| | --56.03%--__hypot_finite
| |
| --0.85%--cabs
~~~~~

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yao Jin <yao.jin@linux.intel.com>
Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
---
tools/perf/util/callchain.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index d1c5d1d422cb..b335fc805472 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -638,11 +638,9 @@ enum match_result {
MATCH_GT,
};

-static enum match_result match_chain_srcline(struct callchain_cursor_node *node,
- struct callchain_list *cnode)
+static enum match_result match_chain_strings(const char *left,
+ const char *right)
{
- const char *left = cnode->srcline;
- const char *right = node->srcline;
enum match_result ret = MATCH_EQ;
int cmp;

@@ -652,10 +650,8 @@ static enum match_result match_chain_srcline(struct callchain_cursor_node *node,
cmp = 1;
else if (left && !right)
cmp = -1;
- else if (cnode->ip == node->ip)
- cmp = 0;
else
- cmp = (cnode->ip < node->ip) ? -1 : 1;
+ return MATCH_ERROR;

if (cmp != 0)
ret = cmp < 0 ? MATCH_LT : MATCH_GT;
@@ -670,10 +666,18 @@ static enum match_result match_chain(struct callchain_cursor_node *node,
u64 left, right;

if (callchain_param.key == CCKEY_SRCLINE) {
- enum match_result match = match_chain_srcline(node, cnode);
+ enum match_result match = match_chain_strings(cnode->srcline,
+ node->srcline);
+
+ /* if no srcline is available, fallback to symbol name */
+ if (match == MATCH_ERROR && cnode->ms.sym && node->sym)
+ match = match_chain_strings(cnode->ms.sym->name,
+ node->sym->name);

if (match != MATCH_ERROR)
return match;
+
+ /* otherwise fall-back to IP-based comparison below */
}

if (cnode->ms.sym && sym && callchain_param.key == CCKEY_FUNCTION) {
--
2.14.2
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