Question

What is the difference between using a new thread and using a thread from the thread pool? What performance benefits are there and why should I consider using a thread from the pool rather than one I’ve explicitly created? I’m thinking specifically of .NET here, but general examples are fine.

Answer 1

Thread pool will provide benefits for frequent and relatively short operations by

• Reusing threads that have already been created instead of creating new ones (an expensive process)
• Throttling the rate of thread creation when there is a burst of requests for new work items (I believe this is only in .NET 3.5)

  • If you queue 100 thread pool tasks, it will only use as many threads as have already been created to service these requests (say 10 for example). The thread pool will make frequent checks (I believe every 500ms in 3.5 SP1) and if there are queued tasks, it will make one new thread. If your tasks are quick, then the number of new threads will be small and reusing the 10 or so threads for the short tasks will be faster than creating 100 threads up front.

  • If your workload consistently has large numbers of thread pool requests coming in, then the thread pool will tune itself to your workload by creating more threads in the pool by the above process so that there are a larger number of threads available to process requests

  • check Here for more in depth info on how the thread pool functions under the hood

Creating a new thread yourself would be more appropriate if the job were going to be relatively long running (probably around a second or two, but it depends on the specific situation)

@Krzysztof – Thread Pool threads are background threads that will stop when the main thread ends. Manually created threads are foreground by default (will keep running after the main thread has ended), but can be set to background before calling Start on them.