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Using Valgrind with Vespa

Valgrind is a useful tool to investigate bugs, and to get a detailed performance profile of an application after profiling to get the higher level picture. This documents how to run Vespa processes with valgrind.

Valgrind with callgrind

Install valgrind. One might need to enable world writeable $VESPA_HOME:

$ sudo chmod 777 $VESPA_HOME

Keep in mind to reset that after profiling session is completed. General use of valgrind - show memory errors:

$ valgrind 'application'

Show callgraph:

$ valgrind --tool=callgrind 'application'

Show a detailed profiling graph - use this to optimize the application:

$ valgrind --tool=callgrind --simulate-hwpref=yes --simulate-cache=yes \
  --dump-instr=yes --collect-jumps=yes 'application'

After running valgrind, copy callgrind.out.* to a host that has kcachegrind installed. Also copy the binary to the same path as it had while running. It might also be nice to have access to the code - path to code can be specified in kcachegrind.

Start Vespa using valgrind

Start Vespa with the following environment variables set:

$ VESPA_USE_VALGRIND="vespa-proton"

Run Vespa under valgrind and check for memory errors (logs in $VESPA_HOME/tmp/):

$ VESPA_USE_VALGRIND="vespa-proton" VESPA_VALGRIND_OPT="--tool=callgrind --simulate-hwpref=yes \
  --simulate-cache=yes --dump-instr=yes --collect-jumps=yes"

Profile the application:

$ VESPA_USE_VALGRIND="vespa-proton" VESPA_VALGRIND_OPT="--tool=callgrind --simulate-hwpref=yes \
  --simulate-wb=yes --dump-instr=yes --collect-jumps=yes --collect-bus=yes --branch-sim=yes"

Remember to stop Vespa - the callgrind.* files are not generated until the program stops.