Sonargraph uses background daemon processes to speed up the parsing process. The daemons only run during refresh and need between 250 MB and 350 MB of memory. Per default the number of daemons is configured to 8. You can change that via setting in the C/C++ preferences to a value between 1 and 16. You should lower the default when your machine is short of memory. You can use a higher value than 8 if you have a high-end CPU and lots of memory. You can also increase the daemon stack size from the default of 1MB. This might be necessary if you have crashing parser daemons. Maximum stack size is 128 MB, which would significantly increase the memory needed per daemon.

Please note that fewer daemons are started if the number of files to parse is smaller than the configured number of daemons.