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RE: Massive HTTP/2 parallel requests

From: Lucas Pardue <>
Date: Fri, 11 Mar 2016 14:46:56 +0000

On Fri, 11 Mar 2016, Molina wrote:

> After a deep search and a parallel email chain with the mod_http2 developers I think found the solution for this:
> The problem was in the window sizes and tcp buffers
> ...
> However, when performing both tests it was necessary to use the nghttp utility to increase the per-connection window size to 16MB and the per-stream window size to 1MB, having 16 parallel streams.

The discussion sounds interesting, is the email chain available on public archives? I'm a little confused how the original issue of a 64 stream limit has ended up as an issue related to TCP buffers. Or did you solve that one and move onto performance tuning?

I could guess that the libcurl window size defaults mean than streams receiving data at an equal rate eventually fill the client connection window and block the server from sending more data. But that would suggest that the clients are not sending WINDOW_UPDATE frames in a timely manner. Can you shed any more light on the process of coming to this solution?


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Received on 2016-03-11