I’m working with the .NET 4.0 MemoryCache class in an application and trying to limit the maximum cache size, but in my tests it does not appear that the cache is actually obeying the limits.

I'm using the settings which, according to MSDN, are supposed to limit the cache size:

  1. CacheMemoryLimitMegabytes: The maximum memory size, in megabytes, that an instance of an object can grow to."
  2. PhysicalMemoryLimitPercentage: "The percentage of physical memory that the cache can use, expressed as an integer value from 1 to 100. The default is zero, which indicates that MemoryCache instances manage their own memory1 based on the amount of memory that is installed on the computer." 1. This is not entirely correct-- any value below 4 is ignored and replaced with 4.

I understand that these values are approximate and not hard limits as the thread that purges the cache is fired every x seconds and is also dependent on the polling interval and other undocumented variables. However even taking into account these variances, I'm seeing wildly inconsistent cache sizes when the first item is being evicted from the cache after setting CacheMemoryLimitMegabytes a

c# .net caching memorycache
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