Precautions

In the running phase after instrumentation, a sampling file can be generated only after a program ends normally. If you run the kill -9 command, the sampling file cannot be generated normally.

If the program cannot exit normally, try the following method to generate a profile (MySQL is used as an example):

echo "set height 0" > gdb.cmd
echo "handle SIGPIPE SIGUSR1 SIGUSR2 SIG36 noprint nostop" >> gdb.cmd
echo "call (void)__llvm_profile_write_file()" >> gdb.cmd
echo "detach" >> gdb.cmd
echo "q" >> gdb.cmd
gdb -x gdb.cmd -p `pidof mysql`

If the error message "counter overflow" is displayed when you merge profiles in step 3, you can add the environment variable LLVM_PROFILE_FILE=$PROFILE_DATA_PATH/code-%p to generate sampling files by process, reducing sampling exceptions caused by coupling between processes.

Parent topic: PGO