Monday, March 30, 2009

How many heaps does the .NET Compact framework use


While discussing the memory architecture with an internal customer, he inquired about how many heaps .NETCF creates. I’m not sure how it might be helpful to users, but the answer is 5. This has been touched upon in some blogs and presentations (e.g. MEDC 2005) but I thought I’d put up a handy list.

Heap Description
JIT heap This is the heap where the buffers of jitted code is placed. Unlike the desktop CLR under some circumstances the CLR does free jitted code by a processed named code-pitching (which I will cover in a later blog post)
GC heap This is where all the managed objects resides. The garbage collector is responsible for managing all objects on this heap including compacting it when it gets fragmented.
Short-term heap This is used for short-lived objects. E.g. while doing a number conversion for the System.Convert methods if temporary space is required by the underlying CLR native code then it is allocated from this heap only to be freed soon.
App-domain This is used by the CLR to place things like assembly meta-data, application/appdomain/thread state information.
Process heap This is the default heap where rest of the stuff goes in

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