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Monday, March 17, 2008

RAM Optimizers/Defragmenters

Myth - "Increasing the amount of available RAM using RAM Optimizers/Defragmenters improves performance."

Reality - "RAM Optimizers have no effect, and at worst, they seriously degrade performance. Although gaining more available memory might seem beneficial, it isn't. As RAM Optimizers force the available-memory counter up, they force other processes' data and code out of memory. Say that you're running Word, for example. As the optimizer forces the available-memory counter up, the text of open documents and the program code that was part of Word's working set before the optimization (and was therefore present in physical memory) must be reread from disk as you continue to edit your document. The act of allocating, then freeing a large amount of virtual memory might, as a conceivable side effect, lead to blocks of contiguous available memory. However, because virtual memory masks the layout of physical memory from processes, processes can't directly benefit from having virtual memory backed by contiguous physical memory. As processes execute and undergo working-set trimming and growth, their virtual-memory-to-physical-memory mappings will become fragmented despite the availability of contiguous memory.

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