This indeed performs excessively poorly, the background GC is not doing you favor here. First thing I noted is that Parallel.ForEach() is using too many tasks. The threadpool manager misinterprets the thread behavior as “bogged down by I/O” and starts extra threads. This makes the problem worse. Workaround for that is: var options = new … Read more
Short version – no, that isn’t possible via an iterator block; the longer version probably involves synchronized queue/dequeue between the caller’s iterator thread (doing the dequeue) and the parallel workers (doing the enqueue); but as a side note – logs are usually IO-bound, and parallelising things that are IO-bound often doesn’t work very well. If … Read more
You can use ParallelEnumerable.WithDegreeOfParallelism: Sets the degree of parallelism to use in a query. Degree of parallelism is the maximum number of concurrently executing tasks that will be used to process the query. var result = Tabel.AsEnumberable() .AsParallel() .WithDegreeOfParallelism(number) .Where(/* predicate */); Edit: @svick provided an excellent on ParallelOptions.MaxDegreeOfParallelism vs PLINQ’s WithDegreeOfParallelism which emphasizes the … Read more
Suppose you have a task to perform. Let’s say you’re a math teacher and you have twenty papers to grade. It takes you two minutes to grade a paper, so it’s going to take you about forty minutes. Now let’s suppose that you decide to hire some assistants to help you grade papers. It takes … Read more
async/await is about asynchrony, whereas Parallel.ForEach is about parallelism. They’re related concepts, but not the same. Parallel.ForEach is used when you want to execute the same operation on all the items in a collection, in parallel, blocking the current thread until all operations have completed. async/await is used when the current operation can’t make any … Read more
The answer is that it is the upper limit for the entire parallel operation, irrespective of the number of cores. So even if you don’t use the CPU because you are waiting on IO, or a lock, no extra tasks will run in parallel, only the maximum that you specifiy. To find this out, I … Read more
async doesn’t work well with ForEach. In particular, your async lambda is being converted to an async void method. There are a number of reasons to avoid async void (as I describe in an MSDN article); one of them is that you can’t easily detect when the async lambda has completed. ASP.NET will see your … Read more
This looks like an ok use of ConcurrentBag. The thread local variables are members of the bag, and will become eligible for garbage collection at the same time the bag is (clearing the contents won’t release them). You are right that a simple List with a lock would suffice for your case. If the work … Read more