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Nine memory management techniques for virtual servers


VMs are able to share content with transparent page sharing

Source:  TechTarget and iStock
Designer: Megan Cassello

VMs that run the same OS, applications or data sets can often have identical memory pages. Compared to the traditional approach of allocating memory to each VM, transparent page sharing allows VMs to share memory pages. This hypervisor uses hash values for each memory page and compares them to find matches. When the hash values line up, the hypervisor checks the pages at the byte level. In the event that there is an exact match, the duplicate memory page is reclaimed. Using transparent page sharing allows you to free up memory for other VMs. The benefits of transparent page sharing are fully realized in virtual environments where VM density is high. A duplicate page will be created if a VM tries to make changes, so the other VMs using that data aren't affected. In Linux KVM, this feature is called kernel samepage merging.

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