Static file performance "staircase" pattern

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

On Sat, May 9, 2015 at 11:37 AM, Dennis J.
[email protected] wrote:

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
information.

Paul

What you should do, to increase the concurrent amount of requests, is to
use domain-sharding, since as Paul mentioned, browsers have between 4
and 8 (actually) simultaneous connections per domain, meaning if you
introduce static1,2,3.domain.com, you will increase your concurrency.

But at same time you also need to be aware, that this can have a
negative effect on your performance if you put too many domains, there’s
no golden rule on how many you need, it’s all a site by site case, and
it differs.
Also take into account your end-users connection can be limiting things
heavily as well if you put too much concurrency (thus negative effect) -
if you have a high number of concurrent requests being processed it will
slow down the download time of each, meaning the perceived performance
that the user see might get worse because it feels like the page is
slower.

  • Lucas

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It’s not really required to serve it from the same sub-domain always.
The most optimal solution would be to add the canonical link header when
serving using domain sharding.

But from a caching perspective, keeping the sharding consistent is
indeed beneficial (you can use crc32 on the image name e.g. this will
always return the same hash, and based on this do the domain sharding),
but from a SEO perspective, it doesn’t matter if you just do it right
with canonical link.


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