Async vs Sync Benchmarks on MVC Controller with Questions

Question

I have set-up the examples from this MSDN article Using Asynchronous Methods in ASP.NET MVC 4 and have done some benchmarking to see what I come up with.

Server Configuration:

• Windows 7 Professional (x64)
• IIS 7.5
• Intel Core i7-2600S @ 2.80HGz
• 8GB Memory
• AppPool > Maximum Worker Processes: 10

I set-up 2 controllers Sync and Async and did some testing using a loader tool for benchmarking. The loader tool just sends 50-60 constant requests for one minute. Each controller is calling the same webservice 3 times. The code for each is below:

---

SYNC:

public ActionResult Sync()
{
    var g1 = GetGizmos("url1");
    var g2 = GetGizmos("url2");
    var g3 = GetGizmos("url3");
    return Content("");
}
    
public object GetGizmos(string uri)
{
    using (WebClient webClient = new WebClient())
    {
        return JsonConvert.DeserializeObject(
         webClient.DownloadString(uri)
        );
    }
}

ASYNC:

public async Task<ActionResult> Async()
{
    var g1 = GetGizmosAsync("url1");
    var g2 = GetGizmosAsync("url2");
    var g3 = GetGizmosAsync("url3");
    var a1 = await g1;
    var a2 = await g2;
    var a3 = await g3;  
    return Content("");
}


public async Task<object> GetGizmosAsync(string uri)
{            
    using (HttpClient httpClient = new HttpClient())
    {
        var response = await httpClient.GetAsync(uri);
        return (await response.Content.ReadAsAsync<object>());
    }
}
    

First question, does anyone know why Async is taking longer, running less and causing timeouts, whereas sync version isn't? I would think using Async for this would be faster, no timeouts, etc. Just doesn't seem right, am I doing something wrong here? What can be done to improve/fix it?

Second question, Using WebRequests in general, is there a way to speed that up? I have set the following in my global.asax but still unsure if the usage is correct:

System.Net.ServicePointManager.DefaultConnectionLimit = 1000;

Also, any other suggestions to help speed up an application performing these types of tasts will be very helpful.

Answer 1

I think the clue is in your comparison

webClient.DownloadString(uri)

to

var response = await httpClient.GetAsync(uri);
return (await response.Content.ReadAsAsync<object>());

maybe you can try

webclient.DownloadStringAsync(uri)

and you could optimize your async code to

await Task.Run(() => {
    // just run your sync code here
    var g1 = GetGizmos("url1");
    var g2 = GetGizmos("url2");
    var g3 = GetGizmos("url3");
    return Content("");
});

It is enough to have one async yielding point here.

Refer to this answer for details about async: Do you have to put Task.Run in a method to make it async?