session_start seems to be very slow (but only sometimes)

Question

For some odd reason, just today our server decided to be very slow during the starting of sessions. For every session_start, the server either times out after 30 seconds, or

Answer 1

I ran into this problem too. It was answered here:

Problem with function session_start() (works slowly)

Sessions are locked by PHP while one script is executing, so if scripts are stacked under the same session, they can cause these surprisingly long delays.