Messages in this thread Patch in this message | | | From | Arnaldo Carvalho de Melo <> | Subject | [PATCH 14/37] perf script: Flush output stream after events in verbose mode | Date | Thu, 25 Oct 2018 08:10:08 -0300 |
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From: Milian Wolff <milian.wolff@kdab.com>
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.wolff@kdab.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: http://lkml.kernel.org/r/20181021191424.16183-2-milian.wolff@kdab.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> --- 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; -- 2.14.4
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