Messages in this thread Patch in this message | | | Subject | Re: [PATCH 2/4] perf annotate: Avoid division by zero when calculating percent | From | Taeung Song <> | Date | Tue, 21 Mar 2017 07:20:20 +0900 |
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And, I tested by perf-stat on the same situation as below.
$ perf stat -e "{cycles,page-faults,branch-misses}" ./old <input.txt 6623856
Performance counter stats for './old':
472,007,763 cycles (99.85%) 71 page-faults (99.85%) 220,073 branch-misses (99.85%)
0.170768608 seconds time elapsed
Many times, the number of samples 'page-faults' was 68 ~ 71. In spite of it, how did the below 'h->sum' is zero..
util/annotate.c:1660~1661
1660 h = annotation__histogram(notes, evidx + k); 1661 src_line->samples[k].percent = 100.0 * h->addr[i] / h->sum;
This patch just add if statement 'if (h->sum)' to handle the case that h->sum is zero. But now I wonder how h->sum could be zero..
I'll dig the problem to find the root cause of it, too !
Thanks, Taeung
On 03/21/2017 07:11 AM, Taeung Song wrote: > Hi Arnaldo :) > > Here the perf.data is, > https://www.dropbox.com/s/nr4nnv8g3cipluf/perf.data?dl=1&pl=1 > > I tested as below. > > $ perf record -e "{cycles,page-faults,branch-misses}" ./old <input.txt > > $ perf annotate --stdio -l -f 2> /dev/null | grep -i nan | head -3 > 29.04 -nan 1.52 old_pack_knapsack.c:34 > 28.27 -nan 0.00 old_pack_knapsack.c:38 > 16.37 -nan 0.00 old_pack_knapsack.c:37 > > > Thanks, > Taeung > > On 03/21/2017 03:15 AM, Arnaldo Carvalho de Melo wrote: >> 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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