https://bugs.kde.org/show_bug.cgi?id=492348
Bug ID: 492348
Summary: Detected nondeterminism in cachegrind reports
Classification: Developer tools
Product: valgrind
Version: 3.18.1
Platform: Ubuntu
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: cachegrind
Assignee: n...@valgrind.org
Reporter: jo.al...@outlook.com
Target Milestone: ---
Created attachment 173070
--> https://bugs.kde.org/attachment.cgi?id=173070&action=edit
A screenshot that shows two runs for the same program running under Valgrind's
Cachegrind tool.
Hi Valgrind Maintainers and Team!
I have been using Valgrind as a tool to check for nondeterministic behaviors
and I know that there are multiple subtools that Valgrind's suite comes with. I
would like to inquire about the Cachegrind subtool in analyzing some of the
reports generated after each run against a binary. While there seems to be
minor differences in values, I felt to raise this issue as we've noticed that
34 out of 41 possible tested repositories yielded changes across those files
and those files all reported consistent values across the board. Would the
team/maintainers care to explain the reasons behind this nondeterminism or
remedy a solution?
Thank you very much!
STEPS TO REPRODUCE
1. Use a GitHub Actions runner with Ubuntu 22.04 + Valgrind 3.18.1 pulled from
the Ubuntu package manager
2. Run your executable with Cachegrind enabled.
3. Convert cachegrind logs to cg_annotate for human-readable format.
OBSERVED RESULT
Specifically, we see that the following fields change drastically during
runtime of the hashcat program (which reported flakiness for 6/10 runs) between
two sample runs. The percents look the same to me except for a few fields, but
the values recorded for a few fields look pretty different.
ADDITIONAL INFORMATION
Refer to the following screenshot of the difference. The red and green here
resembles the removal and additions respectively.
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