In recent local projects, each session_start takes a very long time.

session_start is enabled by default in php.ini
Local projects do not write-lock session files when the traffic is large
There is no problem of too many session files, there are only 4~5 session files.

But session_start still takes a long time.

The framework uses cakephp V0.10.
Using $_SESSION to obtain session does not have this problem.
Using $this->Session->read() will die on session_start.

Changed to save mysql and still exists. It is suspected that the startup failed and was restarted repeatedly.

Please give me some advice on what other problems may cause session_start to start too slowly