x/net/http2: Ability to set initial flow control in transport.

[yonderblue]

What version of Go are you using (go version)?

Go 1.11

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

linux + darwin on amd64 and android on arm.

What did you do?

Made an http2 request.

What did you expect to see?

This is a feature request.

What did you see instead?

Configurable values such as in the Server but for thetransport would be great :D
As the latency gets higher this has a sizable effect.
Currently it is at some huge value for connection and 4MB for stream. In a server that does lots of calls out that might want to be reduced, and in known high latency cases it may go up.

[dmitshur]

/cc @bradfitz @tombergan

[bradfitz]

How does increasing latency affect this?

If anything I'd expect this to increase latency (while reducing CPU / increasing throughput).

Have you run any numbers?

[yonderblue]

@bradfitz Sorry I meant the flow settings that are on the server.

[bradfitz]

I think we have an existing bug open about auto-tuning the various buffers to the calculated bandwidth delay product somewhere. We try to avoid having too many knobs when possible.

[yonderblue]

That would certainly be nice :) for both transport and server. However for servers especially (but might as well both), I would imagine many would still want to cap max memory and therefore even if BDP shows higher is better, a knob would be needed.