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SubjectRe: [PATCH 2/4] perf annotate: Avoid division by zero when calculating percent
Em Mon, Mar 20, 2017 at 11:56:55AM +0900, Taeung Song escreveu:
> Currently perf-annotate with --print-line can print
> -nan(0x8000000000000) because of division by zero
> when calculating percent.
>
> So if a sum of samples is zero, skip calculating percent.

Tried to reproduce it here, couldn't, syswide record:

[root@jouet ~]# perf evlist -v
cycles: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CPU|PERIOD, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1
[root@jouet ~]# perf annotate --stdio -l 2> /dev/null | grep -i nan
[root@jouet ~]#

Can you please send me a perf.data file with this problem? I have to go
thru the code to see how this can take place...

- Arnaldo


> Before:
>
> $ perf annotate --stdio -l
>
> Sorted summary for file /home/taeung/workspace/a.out
> ----------------------------------------------
>
> 32.89 -nan 7.04 a.c:38
> 25.14 -nan 0.00 a.c:34
> 16.26 -nan 56.34 a.c:31
> 15.88 -nan 1.41 a.c:37
> 5.67 -nan 0.00 a.c:39
> 1.13 -nan 35.21 a.c:26
> 0.95 -nan 0.00 a.c:44
> 0.57 -nan 0.00 a.c:32
> Percent | Source code & Disassembly of a.out for cycles (529 samples)
> -----------------------------------------------------------------------------------------
> :
> ...
>
> a.c:26 0.57 -nan 4.23 : 40081a: mov %edi,-0x24(%rbp)
> a.c:26 0.00 -nan 9.86 : 40081d: mov %rsi,-0x30(%rbp)
>
> ...
>
> After:
>
> $ perf annotate --stdio -l
>
> Sorted summary for file /home/taeung/workspace/a.out
> ----------------------------------------------
>
> 32.89 0.00 7.04 a.c:38
> 25.14 0.00 0.00 a.c:34
> 16.26 0.00 56.34 a.c:31
> 15.88 0.00 1.41 a.c:37
> 5.67 0.00 0.00 a.c:39
> 1.13 0.00 35.21 a.c:26
> 0.95 0.00 0.00 a.c:44
> 0.57 0.00 0.00 a.c:32
> Percent | Source code & Disassembly of old for cycles (529 samples)
> -----------------------------------------------------------------------------------------
> :
> ...
>
> a.c:26 0.57 0.00 4.23 : 40081a: mov %edi,-0x24(%rbp)
> a.c:26 0.00 0.00 9.86 : 40081d: mov %rsi,-0x30(%rbp)
>
> ...
>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
> ---
> tools/perf/util/annotate.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> index fc91c6b..9bb43cd 100644
> --- a/tools/perf/util/annotate.c
> +++ b/tools/perf/util/annotate.c
> @@ -1665,11 +1665,15 @@ static int symbol__get_source_line(struct symbol *sym, struct map *map,
> src_line->nr_pcnt = nr_pcnt;
>
> for (k = 0; k < nr_pcnt; k++) {
> + double percent = 0.0;
> +
> h = annotation__histogram(notes, evidx + k);
> - src_line->samples[k].percent = 100.0 * h->addr[i] / h->sum;
> + if (h->sum)
> + percent = 100.0 * h->addr[i] / h->sum;
>
> - if (src_line->samples[k].percent > percent_max)
> - percent_max = src_line->samples[k].percent;
> + if (percent > percent_max)
> + percent_max = percent;
> + src_line->samples[k].percent = percent;
> }
>
> if (percent_max <= 0.5)
> --
> 2.7.4

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