What can cause HTTPS to be slow?

HTTP is really fast, but HTTPS is noticeably much slower on my server, at least for me. When I set it up, I hired a guy to do some tweaking and asked him to look at it, but he said he couldn't find anything in the system that would make HTTPS really slow.

Is this a data-center issue? Maybe a problem with my ISP?

 

Our server is running hardly any load at all

 

hmm... the past few days SSL seems to be causing a heavy load. for the past few hours CPU has been 99% usage by this process:

/usr/local/apache/bin/httpd-DSSL

looking at my mailscanner charts over the past few days (which records current CPU usage), there have recently been a few times when the CPU was at 99% for a few hours with a high load. Also the `CPU/Memory/MySQL Usage` in WHM shows 3 occurances of `/usr/local/apache/bin/httpd -DSSL` using greater than 50% CPU.

 

also right now there are a ton of `/usr/local/apache/bin/httpd -DSSL` processes running and not nearly that many users on the system... seems maybe SSL is running away for some reason?

 

well looking back over the logs, about the time apache began to spin widely out of control is when I installed Turck MMcache.

I disabled it, and so far the problem has not come back. I am keeping an eye on it though.