static file performance "staircase" pattern

Dennis Jacobfeuerborn dennisml at
Sat May 9 17:37:20 UTC 2015

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?

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