Steps to reproduce:
1. Download Unity5_3Project.zip
2. Build for Linux Standalone
3. Run the build
4. Go to: http://localhost:9921/start/0/100
4. Wait for the downloading process to complete
5. Refresh the page (so the assets are loaded from cache)
6. Observe the average load time
7. Repeat steps 4-6, but change the link to: http://localhost:9921/start/0/1000
8. Repeat steps 4-6, but change the link to: http://localhost:9921/start/0/2000

Expected results: the average load time is the same in all 3 cases
Actual results (5.6): When 100 assets are cached average load time is 120ms. 1000 - 200ms, 2000 - 250ms

Reproduced on: 5.6.4p1, 2017.3.0f1
Did not reproduce on (same average load time regardless of the cache size): 5.3.8p2 (~130ms), 5.4.6f2(~100ms), 5.5.5f1 (~190ms)

Notes:
* After testing with a version I cleared the cache folder before testing with another one
* Does not reproduce on macOS
* You can check all the results of the session by going to http://localhost:9921/report/all