Task.WhenAll - async a bit slower than sync

Question

I'm very new to threads. I'm making about 50 OAuth2Client Http calls (implemented as Thread.Wait for simplicity). Method pull_NN_async is not faster than pull_NN. After increasing number of iterations async version time lowered 10% below that of sync version. Still not as expected. Please guide me.

using System.Threading.Tasks;
using System.Collections.Generic;
                    
public class Program
{
internal static List<Task> tasks_list = new List<Task>();   
internal static void Main()
{
   System.Diagnostics.Debug.WriteLine(read_json_and_pull_NN_Async());
   System.Diagnostics.Debug.WriteLine(read_json_and_pull_NN_sync());
}    
internal static long read_json_and_pull_NN_Async()
{
    var watch = System.Diagnostics.Stopwatch.StartNew();
    for (int i=0;i<10;i++)
    {
           Task x = pull_NN_async();
           tasks_list.Add(x);
    }
    await Task.WhenAll(tasks_list);
    watch.Stop();
    return watch.ElapsedMilliseconds;
 }       

internal static long read_json_and_pull_NN_sync()
{
    var watch = System.Diagnostics.Stopwatch.StartNew();
    for (int i=0;i<10;i++)
    {
           pull_NN();
    }
    watch.Stop();
    return watch.ElapsedMilliseconds;
 }       

 private static async Task<int> pull_NN_async() 
 {
    await pull_NN();
    return 0;
 }

 private static Task pull_NN()
 {
     System.Threading.Thread.Sleep(1000); //simulated http OAuth2Client request
     return null;
 }
}

Answer 1

You have a fire and forget task and you have a poorly created async method.

Here's your code written properly:

public class Program
{
    internal static List<Task> tasks_list = new List<Task>();
    internal static async Task Main()
    {
        System.Diagnostics.Debug.WriteLine(await read_json_and_pull_NN_Async());
        System.Diagnostics.Debug.WriteLine(read_json_and_pull_NN_sync());
    }
    internal static async Task<long> read_json_and_pull_NN_Async()
    {
        var watch = System.Diagnostics.Stopwatch.StartNew();
        for (int i = 0; i < 10; i++)
        {
            Task x = pull_NN_async();
            tasks_list.Add(x);
        }
        await Task.WhenAll(tasks_list);
        watch.Stop();
        return watch.ElapsedMilliseconds;
    }

    internal static long read_json_and_pull_NN_sync()
    {
        var watch = System.Diagnostics.Stopwatch.StartNew();
        for (int i = 0; i < 10; i++)
        {
            pull_NN();
        }
        watch.Stop();
        return watch.ElapsedMilliseconds;
    }

    private static async Task pull_NN_async()
    {
        await Task.Delay(TimeSpan.FromSeconds(1.0));
    }

    private static void pull_NN()
    {
        System.Threading.Thread.Sleep(1000);
    }
}