I run simulations on a Windows 64bit-computer with 64 GB RAM. Memory use reaches 55% and after a finished simulation run I remove all objects in the working space by rm(list=ls()), followed by a gc().

I supposed that this would free enough memory for the next simulation run, but actually memory usage drops by just 1%. Consulting a lot of different fora I could not find a satisfactory explanation, only vague comments such as:

"Depending on your operating system, the freed up memory might not be returned to the operating system, but kept in the process space."

I'd like to find information on:

  1. which OS and under which conditions freed memory is not returned to the OS, and
  2. if there is any other remedy than closing R and start it again for the next simulation run?
r garbage-collection
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