static file performance "staircase" pattern

Paul Smith paul.j.smith0 at
Sat May 9 18:03:59 UTC 2015

On Sat, May 9, 2015 at 11:37 AM, Dennis Jacobfeuerborn
<dennisml at> wrote:
> Hi,
> I'm trying to find out how to effectively deliver pages with lots of
> images on a page. Attached you see opening a static html page that
> contains lots of img tags pointing to static images. Please also note
> that all images are cached in the browser (hence the 304 response) so no
> actual data needs to be downloaded.
> All of this is happening on a CentOS 7 system using nginx 1.6.
> The question I have is why is it that the responses get increasingly
> longer? There is nothing else happening on that server and I also tried
> various optimizations like keepalive, multi_accept, epoll,
> open_file_cache, etc. but nothing seems to get rid of that "staircase"
> pattern in the image.
> Does anybody have an idea what the cause is for this behavior and how to
> improve it?
> Regards,
>   Dennis

I am not an expert but I believe that most browsers only make between
4 to 6 simultaneous connections to a domain. So the first round of
requests are sent and the response received and then the second round
go out and are received back and so forth. Doing a search for
something like "max downloads per domain" may bring you better


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