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Re: HTTP 2.0 performance is slower than HTTP 1.1 in libcurl

From: Rajiullah Shammi <>
Date: Mon, 23 May 2016 11:10:18 +0200

Just to inform, by shrinking the H2_BUFSIZE to 16K, I haven’t seen any
improvement in my test (

Mohd. Rajiullah

On Sat, May 21, 2016 at 7:49 PM, Daniel Stenberg <> wrote:

> On Thu, 19 May 2016, Ganesh Nikam wrote:
> are there any configuration changes that can improve HTTP 2.0 performance
>> in above scenarios ?
> It reminded me that we talked about HTTP/2 window handling a while ago
> (like here and I can
> measure a notable speed difference when we send much fewer window updates.
> (I could immediately cut off 13% spent time from my tests over localhost)
> I've also figure out that by shrinking H2_BUFSIZE to 16K, at least single
> stream downloads get an additional extra kick, taking me down to 71% of the
> original times I measured.
> Even with these improvements, I see my tests take about 19% longer time to
> download 512MB over HTTP/2 than HTTP/1.1. This said, I run the HTTP/1 tests
> over stunnel+apache and the HTTP/2 tests with nghttpd, so they're far from
> identical and that may also explain some of the differences. I even think
> they use different TLS ciphers right now.
> None of those changes are really certain yet, but shows there are
> improvements to do and probably more experiments to run. The window size
> thing makes us disable nhttp2's auto handling so we need to add our own
> since we can't bump up the initial value large enough. The buffer size
> needs more tests, especially when a really large amount of parallel streams.
> I made my http2 test program use CURLOPT_DEBUGFUNCTION and in the callback
> I made the 'info' type output the string, including a "delta time": number
> of microseconds since previous invoke. I hoped it would show instances
> where the value would be unusually large and hence indicate waiting or
> pausing.
> Transferring 512MB and then sorting the verbose log based on the delta
> times
> show that sometimes the time is fairly long (hundreds of microseconds,
> sometimes even more). It would indicate that there's something fishy. But
> what? More and deeper research is required.
> --
> /
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Received on 2016-05-23