CPU Utilization and threads

We have a transaction intensive process at one customer site running on a quad core server with four processors. The process is designed to take advantage of every core available. So in this installation, we take an input queue, divide it by 16th's and allocate each fraction of the queue to a core. It works well and keeps up with the transaction volume on the box.

Looking at the CPU utilization on the box, it never seems to go above 33%. Now we have a new customer with at least double the volume of the existing customer. Some of us are arguing that since CPU usage is way below maximum utilization, that we should go with the same configuration.

Others claim t开发者_如何学编程hat there is no direct correlation between cpu utilization and transaction processing speed and since the logic of the underlying software module is based on the number of available cores, that it makes sense to obtain a box with proportionately more cores available for the new client to accommodate the increased traffic volume.

Does anyone have a sense as to who is right in this instance?

Thank you,

To determine the optimum configuration for your new customer, understanding the reason for low CPU usage is paramount.

Very likely, the reason is one of the following:

• Your process is limited by memory bandwidth. In this case, faster RAM will help if supported by the motherboard. If possible, a redesign to limit the amount of data accessed during processing will improve performance. Adding more CPU cores will, on its own, do nothing to improve performance.

• Your process is limited by disk I/O. Using faster disk connections (SATA etc.) and/or upgrading to a SSD might help, but more CPU power will not.

• Your process is limited by synchronization contention. In this case, adding more threads for more cores might even be counter productive. Redesigning your algorithm might help in this case.

Having said this, I have also seen situations where processes that are definitely CPU bound fail to achieve 100% CPU usage on modern processors (Core i7 etc.) because in certain turbo boost relevant cases, task manager will show less than 100%.

As 9000 said, you need to find out what your bottlenecks are when under load. Perfmon might provide enough data to find out.

Another afterthought: You could limit your process on the existing machine to part of the cores (but still at least 30% so that theoretically, CPU doesn't become a bottleneck due to this limitation) and check if overall throughput degrades. If it does not, adding more cores will not improve performance.