Originally posted by: Viditor
Originally posted by: jones377
Common sense works if you know a bit of the things you talk about. I had never even heard of VMMark before a while back when it was shown with various configs. But it has been known for a long time that Opterons have had much lower virtualisation overhead than contemporary Xeons.
Thing is though, VMMark measures the performance of the various virtual servers running on the machine. So even if Nehalem-EX does nothing to reduce the virtualisation overhead compared with Dunnington (something I find very hard to believe since Intel has improved it in every processor update before) it will STILL perform better in VMMark because the apps within the virtual enviroments will see the improvements brought by the Nehalem architecture, including HT. Don't you agree?
Right now Shanghai is only a hair ahead of Dunnington in VMMark. Will Istanbul improve more over Shanghai than Nehalem-EX over Dunnington? I really doubt it. Again no ultimate proof, just an educated guess...
We're getting into areas that are murky again...and believe me, I'm not just saying that to be obstinate (though I don't blame you for thinking so).
Here are some of the questions I have...
1. It's evident that i7's HT has an issue when 4 threads are running. Are there other times (say at 3, 5, 10, or 12 threads) that those issues crop up?
2. How much does virtualization effect the i7's performance?
3. Is there a number of VMs that is affected by HT more than others (say 4 VMs per core)?
4. Is there a change in HT performance when used in multisocket? (by that I mean does an 8 thread program on dual socket i7 have the same problem that a 4 thread program does on single socket?)
5. Are virtual processors effected more than virtual machines?
We've seen enough exceptions that (at least for me) I can't really invest myself in a common sense explanation...there are too many possible variables that wouldn't show up except in hindsight.
For example, common sense would not have shown the problem at 4 threads...
The reason I focus on VMMark is that I know of no other virtualization benchmark that is acceptable. Virtualization (at least with the majority of my clients) is by far the biggest buzz word going right now...especially as a cost cutting effort.