Traditionally in hypervised systems, an operating system manages storage (e.g. maintains the page table, etc.) using service calls to the hypervisor. In environments which set up and tear down huge numbers of short-lived applications (e.g. some types of web serving applications, etc.), the overhead of hypervisor intervention is costly in terms of performance. One approach used by some architectures (e.g. IA32, etc.) has been to create a second level of translation so that the operating system can maintain the first level of page translation, while the hypervisor continues to maintain the actual mapping to real address space. This approach can be costly both in terms of hardware lookaside resources and storage footprint for the tables (and resulting cache pressure). Traditionally, the hypervisor prevents the OS from accessing page tables using conventional storage protection mechanisms that are part of most memory management architectures.
USPTO Backgrounds
USPTO Backgrounds