[Maria-discuss] Reason for changing the thread_pool_size default value?

Hi What was the reason for changing the default thread_pool_size from the number of CPU's to 8? If I look at the history of sql_vars.cc - https://github.com/MariaDB/server/commits/10.1/sql/sys_vars.cc?page=2 - the commit made on the 17th of November still has it as the number of CPU's, but the next commit on the 2nd of December has it at 8. This doesn't appear as a change in the summary. ian