Processor Affinity and why you don’t need it on Hyper-V

re: Processor Affinity and why you don’t need it on Hyper-V

Libor — Thu, 19 May 2011 12:26:05 GMT

There actually might be a situation where setting the affinity could improve the performance. In case of processes that heavily utilize resource sharing (cache, process synchronization) hard-coding the physical(logical) CPU might be beneficial.

What do you think guys?

Libor

re: Processor Affinity and why you don’t need it on Hyper-V

Rick — Tue, 27 Jul 2010 16:12:27 GMT

So you say we never need affinity. What about cases where software needs to be licensed and uses processor, hard drive and NIC? The CPU ID keeps changing and so the license will always FAIL.

re: Processor Affinity and why you don’t need it on Hyper-V

rkc iain jamican homebread ma bredda — Wed, 07 Oct 2009 12:02:28 GMT

i saw the cat and i said you cant just go where you want and he said meow then i said breeahhh

re: Processor Affinity and why you don’t need it on Hyper-V

Josh — Fri, 02 Oct 2009 16:57:15 GMT

@Ravi

Thanks. I looked through that, and it stated a license is required for each virtual processor, which is what I've seen elsewhere as well (I've also seen that each virtual processor is considered to have the same number of cores as the physical processor). The licensing guide here says differently (on page 27 of the PDF it gives a scenario where I would need a single license only, for FOUR virtual processors):

http://www.microsoft.com/sqlserver/2008/en/us/licensing.aspx

This makes much more sense, given that I can licenses multiple physical cores with one SQL license. I wonder which document is accurate, and what I am bound to legally? They are both clearly contradicting papers. Any ideas would be great!!

re: Processor Affinity and why you don’t need it on Hyper-V

Ravi — Thu, 01 Oct 2009 08:00:58 GMT

@Josh

Check this doc on Hyper-V Hosting Guidance. This gives you details on SQL licensing inside Hyper-V guests

http://download.microsoft.com/download/F/5/8/F58E786D-529D-438A-8625-4948205D8BA5/Windows_Hyper_V_Licensing_Whitepaper_v2_0.docx

-Ravi

re: Processor Affinity and why you don’t need it on Hyper-V

Josh — Tue, 29 Sep 2009 22:26:49 GMT

Ben-

If I gather correctly, for SQL licensing, MS licenses by physical processor (not core). A virtual processor ALSO counts as a single processor for licensing purposes. But with the way Hyper-V currently works, isn't the virtual processor basically equivalent to a physical core? So: in a two quad-core processor setup: in order to utilize all 8 of my cores in a virtual environment, I would need to use 8 virtual processors, and pay for 8 SQL processor licenses rather than two (if I installed on the host it would simply be two processor licenses). Another way of stating the same problem: if I create a single VM on my two-processor machine, and assign it four virtual processors, I've just doubled my SQL licensing costs. Is this something that would be simplified with processor affinity options?

Please let me know if I'm looking at it all wrong! I'm very confused.

re: Processor Affinity and why you don’t need it on Hyper-V

Roger Pan — Thu, 24 Sep 2009 22:51:14 GMT

What about the caching benefits you get with hard affinity?

re: Processor Affinity and why you don’t need it on Hyper-V

Philip Lippard — Wed, 23 Sep 2009 21:52:52 GMT

I am having problems with Windows Virtual PCs consuming 100% CPU time after I try to convert over my VPC 2007 VPCs. I have made a blog entry at http://blog.plippard.com/post/2009/09/23/Windows-7-64-bit-Extending-T61p-life-and-improving-performance.aspx

Best to simply skip to the last couple of paragraphs.

Can you advise how to report this problem to MSFT.

There is no appropriate MSDN Newsgroup I can find.

re: Processor Affinity and why you don’t need it on Hyper-V

Peter — Wed, 23 Sep 2009 11:08:26 GMT

What I wonder is that since Hyper-V is limited to a 4 core guest the rest of the available cores on a dual-quad might be getting bored.

Setting it to 100 gives me Just 25%? of total system resources.

re: Processor Affinity and why you don’t need it on Hyper-V

Jason Stevens — Tue, 22 Sep 2009 02:49:11 GMT

Where as say, Virtual PC some tasks will completly become unusable if they don't have their affinity bound to a single cpu core...

But I digress, i know those of use using Virtual PC to maintain legacy OS's are not the focus, nor concern anymore.