Friday, November 11, 2011

Concurrency Profiling

On a daily basis we are working on machines with 4, 8, 12 or even more cores. Not so long ago, 12 cores was considered exotic hardware.

Making apps run well on a multi-threaded environment is a whole study in itself.

One thing that can help along the way is to understand where threads in your application are "stuck" waiting on other threads.

Rather than re-iterate what has already been said quite well - look here

Be aware that if you have worker threads blocking on queues, or waiting for some form of I/O they will show up as "concurrency problems" - ie threads that are blocked.

For your first pass, pretty much ignore these points in your code, the threads are supposed to be blocked there. Focus on the points where you do not expect threads to be blocked.

For you second pass, you may want to consider if you need to think about how many threads you have "waiting" for things to happen. Do you end up loosing too much of you CPU to swapping threads in and out?
Once you get to that level, a short blog post is not going to help you much though.

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