How will SSL affect my machine?s performance?

The performance problems associated with most HTTP servers are CPU and memory related (this contradicts the common assumption that it is always the network which is the problem). The CPU has to process the HTTP request, write out HTTP headers, log the request and put it all on the TCP stack. Memory bandwidth is also a problem (the OS has to make a lot of copies to put packets onto the network). SSL makes this bottleneck more severe.