[LTP] On the performance of lcov...

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Eric Chamberland" <Eric.Chamberland@giref.ulaval.ca>
> To: ltp@lists.linux.it
> Sent: Saturday, 17 December, 2016 7:56:17 PM
> Subject: [LTP] On the performance of lcov...
> 
> Hi,
> 
> We are running gcov+lcov analysis each night for our software.  It does
> a really great job to help us manage our nightly tests database (~1100
> runs) and to discover unused lines of code! :)
> 
> However running lcov+genthml is really time consuming (longer than the
> tests or even compiling the code) and I would like to know if there is a
> way to make lcov+genthml go a little faster...
> 
> Here is the timings for a complete analysis and html generation:
> 
> ===========================
>   660s (1866 .gcno files):  lcov --rc lcov_branch_coverage=1 --capture
> --initial -d $obj/dev -d $obj2/dev -o init.info
> 
> 2113s (1662 .gcda files): lcov --rc lcov_branch_coverage=1 --capture -d
> $obj/dev -d $obj2/dev -o cov.info
> 
> 3112s: lcov --rc lcov_branch_coverage=1 --remove init.info "/usr*"
> "/opt*" "/pmi/Indus*" -o init.info && lcov --rc lcov_branch_coverage=1
> --remove cov.info   "/usr*" "/opt*" "/pmi/Indus*" -o cov.info
> ...
> Deleted 255 files
> Writing data to cov.info
> Summary coverage rate:
>    lines......: 69.4% (357216 of 515067 lines)
>    functions..: 64.1% (61500 of 95942 functions)
>    branches...: 32.1% (717338 of 2232711 branches)
> 
> 2227s:  lcov --rc lcov_branch_coverage=1 -a init.info -a cov.info -o
> total.info
> ...
> Combining tracefiles.
> Reading tracefile init.info
> Reading tracefile cov.info
> Writing data to total.info
> Summary coverage rate:
>    lines......: 64.5% (357216 of 553958 lines)
>    functions..: 60.3% (61500 of 102006 functions)
>    branches...: 32.1% (717338 of 2232711 branches)
> 
> 1391s:  genhtml  --show-details --legend --branch-coverage
> --demangle-cpp -o $$pref_html/coverage_dev total.info
> Reading data file total.info
> Found 2854 entries.
> ...
> ===========================
> 
> total time: 9503s => 2h38m
> 
> We would like to understand if we are doing something wrong... or if
> someone is aware of this performance "problem" or willing to optimize
> lcov/genthml code itself?

Hi,

2 bugs below come to mind, try turning off --all-blocks to see if this is
your case as well. There should an option for that in lcov config file.

Bug 1290759 - gcov takes up to 36hours to process xfs_sb.gcda on Intel Xeon
https://bugzilla.redhat.com/show_bug.cgi?id=1290759

Bug 67992 - GCOV takes an absurdly long time to process a file
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67992

Regards,
Jan

> 
> anyway, thanks for this great tool! :)
> 
> Eric
> 
> 
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