On Aug 29, 2006, at 11:13 PM, Marshall T. Vandegrift wrote: > At least on Linux, the allocation pattern used by these scripts > never causes > the heap implementation to get system memory via m/unmap() (as you > can see > visually in my graphs by how the amount ruby allocates using malloc > () never > goes beyond the size of the heap, even during peak allocation > periods). Right, so brk/sbrk, but in the environment you are testing, the process never actually gives memory back to the kernel. So even if the memory isn't used (i.e. it isn't part of the working set of the process), from the point of view of the kernel it is allocated to the process and so occupies various tables and swap/paging space within the kernel. Gary Wright