do Socket.Receive/SendAsync(Memory<byte>) allocate memory on each call?

[freddyrios]

Specifically I am referring to allocating new AwaitableSocketAsyncEventArgs.

When I read this in the Socket.Tasks file it looked like there would be some reuse:

runtime/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Tasks.cs

Lines 18 to 19 in 8bcbe18

	/// <summary>Cached instance for receive operations that return <see cref="ValueTask{Int32}"/>. Also used for ConnectAsync operations.</summary>
	private AwaitableSocketAsyncEventArgs? _singleBufferReceiveEventArgs;

However, It seems every use sets it to null and do nothing with the previous value (as its null).

This pattern in ConnectAsync is the same in multiple places, including ReceiveAsync. Sets it to null and if the previous value was null creates a new instance (but does not set the field):

runtime/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Tasks.cs

Lines 93 to 96 in 8bcbe18

	// Use _singleBufferReceiveEventArgs so the AwaitableSocketAsyncEventArgs can be re-used later for receives.
	AwaitableSocketAsyncEventArgs saea =
	Interlocked.Exchange(ref _singleBufferReceiveEventArgs, null) ??
	new AwaitableSocketAsyncEventArgs(this, isReceiveForCaching: true);

Sets it to null and if the previous was not null dispose it:

runtime/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Tasks.cs

Line 956 in 8bcbe18

Interlocked.Exchange(ref _singleBufferReceiveEventArgs, null)?.Dispose();

Sets it to null if the previous value matched the current instance + disposes the current instance:

runtime/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Tasks.cs

Lines 1032 to 1036 in 8bcbe18

	ref AwaitableSocketAsyncEventArgs? cache = ref _isReadForCaching ? ref _owner._singleBufferReceiveEventArgs : ref _owner._singleBufferSendEventArgs;
	if (Interlocked.CompareExchange(ref cache, this, null) != null)
	{
	Dispose();
	}

Copies the existing value of the field to another instance:
https://github.com/dotnet/runtime/blob/main/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Unix.cs#L281

[elgonzo]

Sets it to null if the previous value matched the current instance + disposes the current instance:

You did read the Interlocked.CompareExchange wrong. The last parameter in Interlocked.CompareExchange(ref cache, this, null) is the value compared against. Therefore, it sets cache to this if the value of cache is null (and disposes the current instance if there is already some non-null instance in cache).

[freddyrios]

Thanks, that makes more sense, sry for the noise 😅