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Memory management for virtualizationMemory management for virtualizationPosted Apr 8, 2010 21:31 UTC (Thu) by avik (guest, #704)In reply to: Memory management for virtualization by anton Parent article: Memory management for virtualization
Nested paging actually makes things worse: the cache footprint of the page table doubles, and a tlb fill needs 24 memory accesses instead of 4. Large pages are a way to reduce the cache footprint and tlb fill cost to something tolerable.
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Memory management for virtualization Posted Apr 9, 2010 10:36 UTC (Fri) by anton (guest, #25547) [Link] Nested paging makes things worse than what? If it's worse than whatever they do in virtualization without them, why were they introduced?
Memory management for virtualization Posted Apr 9, 2010 10:43 UTC (Fri) by avik (guest, #704) [Link]
Nested paging has worse cache footprint and tlb fill latency than shadow paging. However shadow paging is a lot worse in terms of scalability and mmu operation costs, so nested paging is an overall win (by a large margin).
So, nested paging is overall much better than shadow paging (but worse in some aspects), large pages bridge the gap and make nested paging better overall.
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