HttpRequestStream & DuplexPipeStream don't amortize their ValueTask ReadAsync calls
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affected-very-few
area-networking
enhancement
Perf
severity-nice-to-have
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- C#
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Description
In usage a HttpRequestStream & DuplexPipeStream normally has very many ReadAsync calls made on them. (Use case WebSockets/SignalR over TLS)
Using the ValueTask overloads for these Streams read allocates a AsyncStateMachineBox per read (when data is not immediately available)
However it could use `TryRead` for the sync-path and allocating a IValueTaskSource object the first time that fails to back the async read, and then reuse it each time the read needs to go async again.
Related https://github.com/dotnet/corefx/issues/39258
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