HttpClient use ValueTask internally

[benaadams]

Test code for HttpClient with http

master (Task)

Threads: 1, Request/s: 11,478.0, Time: 87,122 ms, Allocated/Request: 3,200
Threads: 2, Request/s: 24,753.7, Time: 40,398 ms, Allocated/Request: 3,200
Threads: 3, Request/s: 40,130.3, Time: 24,918 ms, Allocated/Request: 3,200
Threads: 4, Request/s: 50,418.6, Time: 19,833 ms, Allocated/Request: 3,199

PR (ValueTask) SET DOTNET_SYSTEM_THREADING_POOLASYNCVALUETASKS=0

Threads: 1, Request/s: 11,308.8, Time: 88,426 ms, Allocated/Request: 3,200
Threads: 2, Request/s: 24,235.0, Time: 41,262 ms, Allocated/Request: 3,200
Threads: 3, Request/s: 39,305.8, Time: 25,441 ms, Allocated/Request: 3,200
Threads: 4, Request/s: 50,888.5, Time: 19,650 ms, Allocated/Request: 3,199

PR (ValueTask) SET DOTNET_SYSTEM_THREADING_POOLASYNCVALUETASKS=1

Threads: 1, Request/s: 11,424.4, Time: 87,531 ms, Allocated/Request: 3,024
Threads: 2, Request/s: 25,417.1, Time: 39,343 ms, Allocated/Request: 3,024
Threads: 3, Request/s: 41,144.7, Time: 24,304 ms, Allocated/Request: 3,024
Threads: 4, Request/s: 52,013.2, Time: 19,225 ms, Allocated/Request: 3,025

"configProperties": {
  "System.GC.Server": true,
  "System.GC.HeapHardLimit": 20971520
}

[stephentoub]

still seems bucket loads.

Having trouble parsing this... bucket?

[stephentoub]

Testing SET DOTNET_SYSTEM_THREADING_POOLASYNCVALUETASKS=1

👍

[benaadams]

still seems bucket loads.

Having trouble parsing this... bucket?

A large amount; requiring several buckets; might be a British colloquialism 😄

[stephentoub]

Oh! :-) I thought you were saying something was loading.

[stephentoub]

Can you share the code you're using?

[benaadams]

Can you share the code you're using?

Still playing with it, aside from memory, bit of a (small) gain when single threaded, looking at multithreaded bit of a (small) loss when mutli-threaded (assume contention) https://gist.github.com/benaadams/cd2969e13c582ab4070489b5c585024e (client and server)

I thought HttpClient was a good sample candidate (being not propriety, easy to share results) since it has many StateMachineBoxes

However, the allocations are still heavy from elsewhere

And can't get rid of all of them due to the public api being Task based :-/

Going to see what happens when going a bit deeper e.g. requesting https so including sslstream in the pipeline

[benaadams]

@stephentoub current code for HttpClient with http

master (Task)

Threads: 1, Request/s: 11,478.0, Time: 87,122 ms, Allocated/Request: 3,200
Threads: 2, Request/s: 24,753.7, Time: 40,398 ms, Allocated/Request: 3,200
Threads: 3, Request/s: 40,130.3, Time: 24,918 ms, Allocated/Request: 3,200
Threads: 4, Request/s: 50,418.6, Time: 19,833 ms, Allocated/Request: 3,199

PR (ValueTask) SET DOTNET_SYSTEM_THREADING_POOLASYNCVALUETASKS=0

Threads: 1, Request/s: 11,308.8, Time: 88,426 ms, Allocated/Request: 3,200
Threads: 2, Request/s: 24,235.0, Time: 41,262 ms, Allocated/Request: 3,200
Threads: 3, Request/s: 39,305.8, Time: 25,441 ms, Allocated/Request: 3,200
Threads: 4, Request/s: 50,888.5, Time: 19,650 ms, Allocated/Request: 3,199

PR (ValueTask) SET DOTNET_SYSTEM_THREADING_POOLASYNCVALUETASKS=1

Threads: 1, Request/s: 11,424.4, Time: 87,531 ms, Allocated/Request: 3,024
Threads: 2, Request/s: 25,417.1, Time: 39,343 ms, Allocated/Request: 3,024
Threads: 3, Request/s: 41,144.7, Time: 24,304 ms, Allocated/Request: 3,024
Threads: 4, Request/s: 52,013.2, Time: 19,225 ms, Allocated/Request: 3,025

"configProperties": {
  "System.GC.Server": true,
  "System.GC.HeapHardLimit": 20971520
}

[stephentoub]

test code

Can you:

• set HttpClient.Timeout to infinite
• pass ResponseHeadersRead to SendAsync

That should reduce some of the noise.

On top of that, you could use the base HttpMessageInvoker instead of the derived HttpClient.

[benaadams]

On top of that, you could use the base HttpMessageInvoker instead of the derived HttpClient.

Changing to
new HttpMessageInvoker(new SocketsHttpHandler(), disposeHandler: false) drops allocs by about 1Kb but also throughput for some reason. Also I'm right in thinking the other changes don't apply as with the Invoker they are HttpClient only?

Will reboot and restart, just incase its caused overnight detritus

[stephentoub]

also throughput for some reason

I'd guess because you're doing 14 1-byte reads on the response stream. Previously HttpClient was buffering the whole response, so your 1-byte reads were all against a memory stream.

[stephentoub]

@benaadams, thanks for this. I'm going to close this for now. Given that there's a small regression when the environment variable isn't set, we should wait to do something like this until it's clearer what the future of the setting will be.