note 93670 deleted from function.session-start by danbrown

Note Submitter: Charlie at NOSPAM dot example dot com ---- As noted before, if you have multiple concurrent requests from same session, they will serialize based upon session_start()-end of script--unless you call session_write_close. Practically speaking this is not usually an issue and using a single global lock over all session use in a script is arguably the simplest effective mechanism. But be warned that depending on end of script to close the session *will serialize concurrent session requests*. Background "data retrieval" (e.g. AJAX or amfphp/Flex) can fall into this trap easily. Holding the session_write_close until after an expensive operation is likewise problematic. To minimize effects, call session_write_close (aka session_commit) as early as practical (e.g. without introducing race conditions) -- often this possible quite early in the script or otherwise avoid the serialization bottleneck.