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What is the purpose of page table?

What is the purpose of page table?

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses.

What is a shadow page table?

The shadow page table is a data structure that is actively maintained and re-filled by the VMM. The shadow page table mirrors what the guest is doing in terms of its own page tables and in terms of what the VMM translates the guest physical address to the host physical address.

Is page A table process?

Each process has its own page table in the kernel. Having a separate page table for each process is necessary for process isolation as they should not be allowed to stomp on each others memory. Since each process has a different page table, there is not one pmap that will work for every process.

What are extended page tables?

“Extended page tables” are Intel’s implementation of Second Level Address Translation (SLAT), also known as nested paging, which is used to more efficiently virtualize the memory of guest VMs.

What is a KVM image?

Overview. Kernel-based Virtual Machine (KVM) is an open source virtualization technology built into Linux®. Specifically, KVM lets you turn Linux into a hypervisor that allows a host machine to run multiple, isolated virtual environments called guests or virtual machines (VMs).

How does a shadow page table work?

Shadow page tables are used by the hypervisor to keep track of the state in which the guest “thinks” its page tables should be. The guest can’t be allowed access to the hardware page tables because then it would essentially have control of the machine.

What is Hyper-V Smart paging?

Smart paging is an advanced version of memory paging in Windows Server 2012 Hyper-V. Smart paging allows a virtual machine (VM) to temporarily use hard disk space to supplement shortages of non-volatile memory. Smart paging is only used during VM restarts when there is no available physical memory.

How many pages in a shadow page table?

Page table has n entries – one for each database page. Each contain pointer to a page on disk (1 to 1st page on database and so on…). The idea is to maintain 2 pages tables during the life of transaction. The shadow page table is never changed over the duration of the transaction.

What’s the point of shadow paging in SQL?

The key idea behind the shadow-paging technique is to maintain two page tables during the life of a transaction: the current page table and the shadow page table. When the transaction starts, both page tables are identical. The shadow page table is

How are pages mapped in shadow paging technique?

In this recovery technique, database is considered as made up of fixed size of logical units of storage which are referred as pages. pages are mapped into physical blocks of storage, with help of the page table which allow one entry for each logical page of database. This method uses two page tables named current page table and shadow page table.

What happens to shadow page table after transaction?

After this, shadow page table gets saved on disk and current page table is going to be used for transaction. Entries present in current page table may be changed during execution but in shadow page table it never get changed. After transaction, both tables become identical. This technique is also known as Cut-of-Place updating.