Php-fpm Too many open files

I am running nginx as frontend and php-fpm as the backend for php prcesss files. I get the message "Too many open files" on my / var / log / php -fpm / error.log. I increased hard and soft ulimit to 65535 and it seems that it cannot solve the problem.

/var/log/php-fpm/error.log

[17-Sep-2012 14:43:51] ERROR: failed to prepare the stderr pipe: Too many open files (24)
[17-Sep-2012 14:43:52] ERROR: failed to prepare the stderr pipe: Too many open files (24)

ulimit -n

65535

/etc/php-fpm/www.conf

rlimit_files = 65535