Recenly faced iis related memory leakage, To investigate its happen application level or system level.
Application level
i. Check DB - costly query and DB performance
ii. outputcache
iii. third-party dll and excel macro relate application used
System level
i. To reduce number application pool (each application pool allocating memory, so allocate static site are to defaultapppool)
ii. check system configuration (RAM and C drive space)
I referred below links,
IIS - Output cache: https://serverfault.com/questions/557920/iis-memory-management-thresholds-with-potential-leaks
Memory: https://forums.iis.net/t/1230103.aspx?Windows+Server+2012+IIS+8+0+IIS+Worker+Process+Consumes+more+memory
Recycling: http://www.bursky.net/index.php/2013/03/managing-iis-server-memory-usage/
https://stackoverflow.com/questions/16162524/how-to-increase-memory-and-cache-size-for-application-pool-in-iis-7-efficiently
https://serverfault.com/questions/598672/app-pool-doesnt-respect-memory-limits
