Strace Apache process output showing 24 seconds wait?What can be the reason?

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http://serverfault.com – Performed strace on one one of the apache children and its showing 24 seconds between two system calls.How can i determine what is the cause of this behavior.It looks like both children are taking almost same amound of time(24.7 and 23.92) seconds. we are using apache prefork with php5 and mysql 5 /var/lib/php5/ is the php session folder strace output of apache children1 with processid -20539 ps -u www-data | grep apache2 | awk '{print"-p " $1}' | xargs strace -o /strace/strace.log -ff -s4096 -r 20539 0.000064 close(13) = 0 20539 0.000060 open("/var/lib/php (HowTos)