For shared-mem/mmap operations, you can't rely on ps, as every process that mmap's a file will have it included in it's total memory usage. There is really only a single copy in RAM for the OS -- it is simply mapped into different locations of different processes. When a given process munmaps a file, its 'ps' memory usage will say it is smaller, but the memory is still in use in the other processes. Only if it is the last process to have the file mapped will the memory actually be 'returned' to the OS. And, again, mmap is generally only used for shared libraries.

In reply to Re^3: demonstrate that perl can give back memory to the OS by Illuminatus
in thread demonstrate that perl can give back memory to the OS by perl5ever

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