[chrisseaton]

"Unless you're a mathematician or theoretical physicist the gross of your CPU time will be spent waiting for IO"

As someone working in VM research, I'm not entirely convinced this is true. Perhaps we should do some work to find out where most web applications really do spend their time.

Here's one real-world example: Rap Genius. They certainly aren't mathematicians or theoretical physicists, all they do is process text I think, but it appears they spend over half their time in the Ruby interpreter - not waiting on network or database (if I'm reading the graph correctly).

http://images.rapgenius.com/75aa2143d3e9bf6b769fc9066f6c40c8...

[valarauca1]

I can't find the blog post, and the above poster likely knows more then me.

I remember seeing a post several years ago that XEN increases the likelihood of cache misses by 25-50%. Thus while the CPU looks to be at 100% processing power its really waiting on RAM/cache.