[cube13]

>If memory usage is so much higher than CPU usage, I have to wonder what it is that Mozilla is doing wrong with their architecture. Are they using pre-fork-style servers? Are they just provisioning poorly? What is it?

Or are they just serving up web pages to users? That's RAM and bandwidth heavy, but very CPU light. You still need the machines to scale your load, but you're not going to be using the CPU.

Realistically, for just about any application, you're going to be RAM-bound before you're CPU-bound. The exceptions are(off the top of my head) scientific computing and video rendering, both of which are CPU heavy, and are very deterministic in their behaviors, which allows for heavy optimization of L2 and L3 cache misses.

[flatline3]

> Or are they just serving up web pages to users? That's RAM and bandwidth heavy, but very CPU light. You still need the machines to scale your load, but you're not going to be using the CPU.

That depends very much on the efficiency of software your architecture. A well-architected web app can scale up RAM and CPU utilization much more closely than something modeled on zero shared state independent processes.

Additionally, even if your scaling model of RAM before CPU is the only possible one, that doesn't make the utilization effecient, and implies that higher efficiency could still be reached by scaling up RAM per machine.