upstream prematurely closed connection while reading response header from upstream

[jdzcn]

nginx0.6.36+php5.2.9+php-fpm
ab -n 2000 -c 2000 http://www.test.com/
i  has many error 
2009/05/23 16:00:30  24601#0: *81788 upstream prematurely closed connection while reading response header from upstream, client: 192.168.1.11, server: www.test.com, request: "GET / HTTP/1.0", upstream: "fastcgi://127.0.0.1:9000", host: "www.test.com"

can you help me?
thanks

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,2326,2326#msg-2326