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> There is no performance gain for most people using async/await, at all. That's simply not how it works. You have to be in a specific scenario, high load on th

> There is no performance gain for most people using async/await, at all. That's simply not how it works. You have to be in a specific scenario, high load on the server's resources, not the DB, to see any benefit. If you have two asynchronous things to do, and they are unrelated, start them both and then await Task.WhenAll(file1Download, file2Download). Look at the wall clock - it's up to twice as fast. Look ma, no threads or synchronization primitives! > And while keeping the UI thread unlocked is great, how many people are using this in C# web code instead? Where the entire web pipeline is already set up to naturally multi-thread by itself. Blocking operations ... block. Now your thread is doing nothing while your database churns/disk writes/network packet streams. As I understand it, using async/await with the SynchronizationContext in ASP.NET will yield the thread to another request. You get more requests per thread, which mitigates the problems with thread-per-request as described here [1]. Instead it's a combination of thread-based and event-driven models. [1] http://berb.github.io/diploma-thesis/original/042_serverarch.html#scalemt http://berb.github.io/diploma-thesis/original/042_serverarch...

mattmanser 10y ago
Not a lot of things need to access two files at once. You and I both know virtually all await/asyncs are doing a singular one thing like DB or emailing or a single file access. So why bring it up? And as for your condescending "Blocking operations ... block", talk about missing my entire point. IIS is the victorian sewer, your code is the hose. IIS has many threads available to it, that's my entire point. You don't need async/await to free up those threads, it's got a ton of them ready to go. Most programmers are not going to hit the thread limit, and when they do they can upgrade hardware while they figure out the tiny few high-impact async/awaits that would actually mitigate the problem. It's pointless pre-optimization. We all talk about how evil it is, so why is it suddenly not evil with async/await?
- taspeotis 10y ago
  I make plenty use of async requests to get files (images) and make web service calls at the same time. It's a Xamarin mobile application. Mobile apps are sometimes constrained by latency, so having a few requests in flight at once speeds things up. Performance is not just fewer CPU cycles. > IIS has many threads available to it, that's my entire point My web services run on a VM with four cores. That's what I get given, and there's another twenty websites on it. The less overhead my code has the better. Just because it's not 100K TPS doesn't mean there aren't benefits.

mattmanser 10y ago

Not a lot of things need to access two files at once. You and I both know virtually all await/asyncs are doing a singular one thing like DB or emailing or a single file access. So why bring it up? And as for your condescending "Blocking operations ... block", talk about missing my entire point. IIS is the victorian sewer, your code is the hose. IIS has many threads available to it, that's my entire point. You don't need async/await to free up those threads, it's got a ton of them ready to go. Most programmers are not going to hit the thread limit, and when they do they can upgrade hardware while they figure out the tiny few high-impact async/awaits that would actually mitigate the problem. It's pointless pre-optimization. We all talk about how evil it is, so why is it suddenly not evil with async/await?

taspeotis 10y ago
I make plenty use of async requests to get files (images) and make web service calls at the same time. It's a Xamarin mobile application. Mobile apps are sometimes constrained by latency, so having a few requests in flight at once speeds things up. Performance is not just fewer CPU cycles. > IIS has many threads available to it, that's my entire point My web services run on a VM with four cores. That's what I get given, and there's another twenty websites on it. The less overhead my code has the better. Just because it's not 100K TPS doesn't mean there aren't benefits.