This article is a follow-up to Red Hat Enterprise Linux 5.1 utilizes nested paging on AMD Barcelona Processor to improve performance of virtualized guests.
With new hardware releases, customers are faced with situations in which they want to take advantage of increased speeds but are forced to stay on older hardware because their operating environments are not supported on the newer hardware. Virtualizing their operating environment helps them get past this issue. Virtualization also helps them:
RHEL 5 virtualization lets customers virtualize their existing systems and take advantage of the benefits mentioned above. » Read more
by Sanjay Rao
Red Hat® Enterprise Linux® (RHEL) 5.1 provides paravirtualized (PV) drivers for guest operating systems to improve I/O performance for I/O intensive disk or network applications.
In addition, RHEL 5.1 supports a feature called “nested paging,” available on AMD Barcelona processors, that translates guest virtual memory addresses to machine physical addresses using two-level translation in the hardware. Without nested paging, the hypervisor marks all page table pages as read only. So whenever the guest tries to update a page table, the call is trapped by the hypervisor that does the update. The shadow page tables on the guest are refreshed on a context switch, resulting in TLB misses on the guest. With nested paging, page tables are not refreshed with context switches, lowering the TLB miss count. The hypervisor also does not need to trap the updates to the page tables, since the hardware does the translation. » Read more
