How many threads can I run concurrently?

Question

A comment to another of my questions says that I can only run \"so many\" threads concurrently, a notion which I have seen elsewhere.

As a threading novice, how can

Answer 1

Typically, the number of threads the run truly concurrently is determined by the number of CPUs and CPU cores (including hyper threading) you have. That is to say that at any given time the number of threads running (in the operating system) is equal to the number of "cores".

How many threads you can run concurrently in your app depends on a large number of factors. The best (lay man's) number would be the number of cores on the machine but of course that's like pretending no one (no other application) else exists :).

Frankly, I'd say do a lot more study on multi-threading in .NET/Windows because one tends to do more "damage" than good when one doesn't have a really solid understanding. .NET has the concept of a thread pool and you need to know how that works in addition to Windows.

In .NET 3.5/4.0 you should be looking at Tasks (Task Parallel Library) as the library does a much better job of determining how many threads (if at all) to spawn. With the TPL the threadpool gets a major overhaul and it is a lot smarter about spawning threads and task stealing etc. But you typically work with Tasks and not threads.

This is a complex area and as a result, the .NET framework introduced Tasks so as to abstract programmers from threads and therefore allowing the runtime to be smart about this while the programmer just say what she wants and not so much about how to do it.