When the perf script output is written to a terminal stream,
the normal output of `perf script` would get buffered, but its
debug output would be written directly. This made it quite hard
to figure out where a given debug output is coming from. We can
improve on this by flushing the output buffer after processing an
event. To see the value, compare the following output for a
`perf script -v` run:
Before this patch:
```
unwind: reg 16, val 7faf7dfdc000
unwind: reg 7, val 7ffc80811e30
unwind: find_proc_info dso /usr/lib/ld-2.28.so
unwind: reg 6, val 0
unwind: _start:ip = 0x7faf7dfdc000 (0x2000)
unwind: reg 16, val 7faf7dfdc000
unwind: reg 7, val 7ffc80811e30
unwind: find_proc_info dso /usr/lib/ld-2.28.so
unwind: reg 6, val 0
unwind: _start:ip = 0x7faf7dfdc000 (0x2000)
unwind: reg 16, val 7faf7dfdc000
unwind: reg 7, val 7ffc80811e30
unwind: find_proc_info dso /usr/lib/ld-2.28.so
unwind: reg 6, val 0
unwind: _start:ip = 0x7faf7dfdc000 (0x2000)
unwind: reg 16, val 7faf7dfdc000
unwind: reg 7, val 7ffc80811e30
... lots and lots of verbose debug output
cpp-inlining 24617 90229.122036534: 1 cycles:uppp:
7faf7dfdc000 _start+0x0 (/usr/lib/ld-2.28.so)
cpp-inlining 24617 90229.122043974: 1 cycles:uppp:
7faf7dfdc000 _start+0x0 (/usr/lib/ld-2.28.so)
...
```
After this patch:
```
...
unwind: reg 16, val 7faf7dfdc000
unwind: reg 7, val 7ffc80811e30
unwind: find_proc_info dso /usr/lib/ld-2.28.so
unwind: reg 6, val 0
unwind: _start:ip = 0x7faf7dfdc000 (0x2000)
cpp-inlining 24617 90229.122036534: 1 cycles:uppp:
7faf7dfdc000 _start+0x0 (/usr/lib/ld-2.28.so)
unwind: reg 16, val 7faf7dfdc000
unwind: reg 7, val 7ffc80811e30
unwind: find_proc_info dso /usr/lib/ld-2.28.so
unwind: reg 6, val 0
unwind: _start:ip = 0x7faf7dfdc000 (0x2000)
cpp-inlining 24617 90229.122043974: 1 cycles:uppp:
7faf7dfdc000 _start+0x0 (/usr/lib/ld-2.28.so)
...
```
This new output format makes it much easier to use perf script
output for debugging purposes, e.g. to investigate broken dwarf
unwinding.
Signed-off-by: Milian Wolff <milian.wo...@kdab.com>
Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
---
tools/perf/builtin-script.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index bd468b90801b..ca09b7d2adb7 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -1737,6 +1737,9 @@ static void process_event(struct perf_script *script,
if (PRINT_FIELD(METRIC))
perf_sample__fprint_metric(script, thread, evsel, sample, fp);
+
+ if (verbose)
+ fflush(fp);
}
static struct scripting_ops *scripting_ops;
--
2.19.1
