Skip to main content

VMware does a performance study on AMD's RVI

Nice read, this doc.

In a native system the operating system maintains a mapping of logical page numbers (LPNs) to physical page numbers (PPNs) in page table structures. When a logical address is accessed, the hardware walks these page tables to determine the corresponding physical address. For faster memory access the x86 hardware caches the most recently used LPN->PPN mappings in its translation lookaside buffer (TLB).

In a virtualized system the guest operating system maintains page tables just like in a native system, but the VMM maintains an additional mapping of PPNs to machine page numbers (MPNs). In shadow paging the VMM maintains PPN->MPN mappings in its internal data structures and stores LPN->MPN mappings in shadow page tables that are exposed to the hardware. The most recently used LPN->MPN translations are cached in the hardware TLB. The VMM keeps these shadow page tables synchronized to the guest page tables. This synchronization introduces virtualization overhead when the guest updates its page tables.
Using RVI, the guest operating system continues to maintain LPN->PPN mappings in the guest page tables, but the VMM maintains PPN->MPN mappings in a second level of page tables, called nested page tables. When a logical address is accessed, the hardware walks the guest page tables as in the case of native execution, but for every PPN accessed during the guest page table walk, the hardware also walks the nested page tables to determine the corresponding MPN. This composite translation eliminates the need to maintain shadow page tables and synchronize them with the guest page tables. However the extra operation also increases the cost of a page walk, thereby impacting the performance of applications that stress the TLB. This cost can be
reduced by using large pages, thus reducing the stress on the TLB for applications with good spatial locality.

For optimal performance the ESX VMM and VMkernel aggressively try to use large pages for their own memory when RVI is used.


Get the Whitepaper here

Comments

Popular posts from this blog

Redhot Future Of IT Part I :Marketing yourself as IT professional

I had promised about the "RedHot IT Future Series" and so we discuss here how you should market yourself EFFECTIVELY as an IT professional in this new (and dangerous) web age! Web is the place where you're a hero today and villain tomorrow. While there are lots of professionals who are active on the web, not all are enjoying a good reputation as they got "personal" with others and got into a cockfight. The passive IT professional has nothing to lose but nothing to gain at all!

I know "marketing" might seem as a greasy term but the idea is to have the truth about you out there. You know you're a good person and your family knows that you're really smart person but the rest of the world doesn't!

So the question is how do I market myself on the web as a true "nouveau IT professional". A guy who companies will be tempted to pick up the phone as say "Hey, we wanna talk with you. Can you fly over to Palo Alto (or Guatemala or Johan…

Redhot Future Of IT Part 2 :Virtualized Workplaces

Click on the title to hear what I have to say, alternatively click here to listen to what I have to say here.

So what is a virtualized workplace? Does it mean it does not exist? That it's virtual? Well in a certain way YES. This is where the future of our workplace is going to be. Well it is already a reality in some countries.

OK lets start by asking ourselves these questions:
Do you really bond with your colleagues? (think Team cohesiveness)
Do you spend great amount of hours talking about great things that you will do together? (think collaboration)
Do you really feel that you give 100% at work? (think effectiveness)
What do you really miss at your desk? (think personalization)
Is your desk comfortable enough? (Again think optimizing personalization, OK you have done your best to make it your place)Does it really matter to your employer that you are there for him/her? (think commitment)
Or do you get micromanaged over petty issues? (think mismanagement)
Do you see your employees perfor…

Avastu Blog is migrating to IdeationCloud.com; 1st Jan 2009 live

YOU DON'T HAVE TO DO ANYTHING. WITHIN 2 SECONDS YOU WILL BE REDIRECTED TO THE NEW HOME OF AVASTU BLOG. PLEASE DO UPDATE AVASTU BLOG'S URL to : http://www.ideationcloud.com on your website.

I will send out emails personally to those who are using my link(s) on their sites.

Thanks much for your co-operation and hope you enjoy the new site and its cool new features :-)




Not like the site is unlive or something..on the contrary, its beginning to get a lot of attention already. Well most of the work is done, you don't have to worry about anything though:

What won't change

Links/Referrals: I will be redirecting the links (all links which you may have cross-posted) to IdeationCloud.com - so you don't have to do anything in all your posts and links. Although, I would urge however that you do change the permalinks, especially on your blogs etc yourselfThis blog is not going away anywhere but within a few months, I will consider discontinuing its usage. I won't obviously do …