Sea-change alert…
For a while now, there has been a drive to lower power consumption in the datacenter. It began with virtualization density, continues with linux containers (fun posts coming soon on that), newer processors and their power-sipping variants, CPU frequency governors, CPU idle drivers, and new architectures like ARM and Intel’s Atom.
The sea change I’m alluding to is that with all of this churn in the hardware and kernel space, applications may have not kept up with what’s necessary to achieve top performance. My contact with customers and co-workers has surfaced a very important detail: application developers expect the hardware and kernel to “do the right thing”, and rightfully so. But customer-driven industry trends such as reduced power consumption have a side-effect: reduced performance.
Circling back to the title of this article…again, for a number of years the assumption by developers that full-bore CPU power is available 100% of the time is somewhat mis-leading. After all, when you shell out for those fancy new chips, you get what you pay for, right ? 🙂 The hardware and CPU frequency/idle drivers are biased towards power savings, I personally believe due to industry pressure, in their default configurations. If you’ve read some of my previous posts, you understand the situation, know how to turn all of that off during runtime, and get excellent performance at the price of power consumption.
But there’s got to be some sort of middle-ground…and in fact, our experiments have proven a few options for customers. For example…if you look at the C-state exit latencies on a Sandy Bridge CPU
