如何优化php进程内存使用情况？

I am running a wordpress site and each PHP process usage about 200mb to 250mb resident size memory. With 16GB of ram, the server can only handle about 70 processes. By increasing the virtual memory to 16GB it can handle 140. After that the load keeps rising. If there are 200 connections in 10 minutes, the server load reaches 20 on a 3Ghz quad-core xeon processor!I am running a wordpress site and each PHP proc