CODEWITHSUNDEEP
c#.netmultithreadingasync-await
axk
axk

Reputation: 5394

Continuation on multiple concurrent threads in async method after async IO API call

If I have this

static void Main(string[] args)
{
    var tasks = new List<Task>();
    for (int i = 0; i < 10; i++)
    {
        tasks.Add(AsyncWithBlockingIO(i));
    }

    Task.WaitAll(tasks.ToArray());
}

private static async Task AsyncWithBlockingIO(int fileNum)
{
    var result = await File.ReadAllTextAsync($"File{fileNum}").ConfigureAwait(false);
    //will the below run concurrently on multiple threads?
    CpuNoIOWork(result);
}

Will CpuNoIOWork() run concurrently on multiple threads (using the thread pool) as the IO calls complete or will it only use 1 thread at a time?

Upvotes: 0

Views: 313

Answers (1)

Stephen Cleary
Stephen Cleary

Reputation: 456687

Will CpuNoIOWork() run concurrently on multiple threads (using the thread pool) as the IO calls complete or will it only use 1 thread at a time?

It will run concurrently, on thread pool threads.

However, depending on the internals of what you're awaiting, it might continue on an I/O thread pool thread, which is not desirable. If you have CPU-bound work, I recommend wrapping that in Task.Run, which will ensure the work will be run on a worker thread pool thread:

var result = await File.ReadAllTextAsync($"File{fileNum}").ConfigureAwait(false);
await Task.Run(() => CpuNoIOWork(result));

Upvotes: 7

Related Questions