I host a website that as a part of it's service the website creates cool little PNG avatars for users based on their skin in a game.
I am caching all images in a cache directory for 4 hours to prevent hitting the game's servers and to decrease loading time for the images, but after a year or two of doing this I noticed that load times of avatars increase as there are more cached images in the directory, which looks strange to me because I do not make my script iterate through the entire directorty until it finds the cached image it was looking for.
And here are some benchmarks in cURL:
First test; 400 cached images:
-------
time_namelookup: 0.000
time_connect: 0.093
time_appconnect: 0.000
time_pretransfer: 0.093
time_redirect: 0.000
time_starttransfer: 0.452
----------
time_total: 0.452
Second test; after deleting all of the cache:
time_namelookup: 0.000
time_connect: 0.093
time_appconnect: 0.000
time_pretransfer: 0.093
time_redirect: 0.000
time_starttransfer: 0.249
----------
time_total: 0.249
So, is there any specific reason why the loading time is decreased with less cache in the directory? And is there a way to optimize that?
Edit
The way the requests are made is that whenever somebody requests an avatar the script checks if there is a cached image with his username.
It does that with PHP's file_exists()
