PHPSessionTimeOut的有关问题

PHP SessionTimeOut的问题
画面在操作的情况下，一样计算时间。给Timeout掉了。为什么？
是哪里设置错误？
下面是PHP.ini的Session配置部分。。。还请各位大虾帮着解决以下。。。


[Session]
; Handler used to store/retrieve data.
session.save_handler = files

; Argument passed to save_handler. In the case of files, this is the path
; where data files are stored. Note: Windows users have to change this
; variable in order to use PHP 's session functions.
;
; As of PHP 4.0.1, you can define the path as:
;
; session.save_path = "N;/path "
;
; where N is an integer. Instead of storing all the session files in
; /path, what this will do is use subdirectories N-levels deep, and
; store the session data in those directories. This is useful if you
; or your OS have problems with lots of files in one directory, and is
; a more efficient layout for servers that handle lots of sessions.
;
; NOTE 1: PHP will not create this directory structure automatically.
; You can use the script in the ext/session dir for that purpose.
; NOTE 2: See the section on garbage collection below if you choose to
; use subdirectories for session storage
;
; The file storage module creates files using mode 600 by default.
; You can change that by using
;
; session.save_path = "N;MODE;/path "
;
; where MODE is the octal representation of the mode. Note that this
; does not overwrite the process 's umask.
;session.save_path = "/tmp "

; Whether to use cookies.
session.use_cookies = 1

;session.cookie_secure =

; This option enables administrators to make their users invulnerable to
; attacks which involve passing session ids in URLs; defaults to 0.
; session.use_only_cookies = 1

; Name of the session (used as cookie name).
session.name = sessionName

; Initialize session on request startup.
session.auto_start = 1

; Lifetime in seconds of cookie or, if 0, until browser is restarted.