Increase workerThreads and completionPortThreads defaults for Helios

[kevinchalet]

The default values for the thread pool seem really low under Helios. I personally get workerThreads = completionPortThreads = 16 on a Core i7 machine with 4 cores and hyper-threading enabled (= 8 cores).

An ASP.NET Web Forms app running IIS Express on the same machine comes with far higher default values: workerThreads = 4096 and completionPortThreads = 1000.

You should consider increasing these values to get rid of these weird exceptions:

InvalidOperationException: There were not enough free threads in the ThreadPool to complete the operation.

In the meantime, manually calling ThreadPool.SetMaxThreads with higher values will do the trick.

[Eilon]

@GrabYourPitchforks / @Tratcher thoughts?

[Tratcher]

I'd guess this is not Helios specific, but regarding KRE and how it sets (or doesn't set) defaults when it spins up the CLR.

[kevinchalet]

@pksorensen on JabbR had similar issues with the "Katana version" of Helios and that's why I immediately thought it was Helios and not KRE. I'll ask him to check his TP values.

[Tratcher]

The OWIN/Katana Helios starts the CLR itself, so yes it would be responsible for setting these kinds of defaults.

[davidfowl]

@GrabYourPitchforks This is an issue with Helios specifically. WebEngine4 sets the limits to 2 * cpuCount and normally System.Web sets the limits to 1000 and 4096 (basically the autoConfig settings in web.config).

[Tratcher]

@davidfowl Wouldn't we want to do the same thing in Hosting?

[cdeutsch]

I've been running into the "There were not enough free threads in the ThreadPool to complete the operation" error a lot on a project at work.

This is likely the culprit: workerThreads = completionPortThreads = 4

Is there a recommendation for how to calculate those two values until a fix lands?

Thanks

[kevinchalet]

@crdeutsch you can simply add ThreadPool.SetMaxThreads(4096, 1000) at the top of your Startup.Configure method to fix this issue (these are the default values used by System.Web, as said earlier by @davidfowl).

If you find these values a bit high, you can also limit the worker threads to 100 * cpu-count (that's how ProcessModelSection.DefaultMaxWorkerThreadsForAutoConfig computes the default value)

[pranavkm]

@davidfowl @yishaigalatzer says they also saw this being set in the machine.config. Presumably this is equivalent to setting this in root web.config.

[danroth27]

See https://github.com/aspnet/Helios/commit/c9be2ee17fd53d81ae75147046306d20cd1aea39 for the new defaults.

[kevinchalet]

@danroth27 this repository is not public yet. That would be cool if you could directly share some of the details here.