Alan:
Thanks for your input, but in re-reading my post, I phrased it incorrectly; the question (which I think you really answered in the affirmative) was: will placing the present 2nd-level VMs (and their current 3rd-level guests) in a separate LPAR help my throughput? I believe you answered "yes" - but should I push for a Z9 instead? I assume the Z800 cannot be upgraded. I need to find a solution that will be viable for future hardware/software combinations also, if possible. If different hardware is the solution, then that is what I must suggest. And if different hardware COUPLED with moving all present 2nd-level VMs to their own LPAR, then I need to suggest that!
I am not relishing the administrative headaches, but right now, we have a bigger problem with the clients' throughput!
David Wakser
InfoCrossing
-----Original Message-----
From: Alan Altmark [mailto:[EMAIL PROTECTED]]
Sent: Friday, July 28, 2006 6:01 PM
To: IBMVM@LISTSERV.UARK.EDU
Subject: Re: Performance under z/VM 5.1
On Friday, 07/28/2006 at 11:47 AST, "Wakser, David"
<[EMAIL PROTECTED]> wrote:
> You have asked the correct question, since I am pretty certain
> that
the SIE
> is the problem (older VMs had 3, and that was reduced). Any answers to
the
> question: will replacing a single LPAR running z/VM (and 2nd level
> z/VMs
with
> 3rd level guests) have any advantage?
There will be performance advantages, yes. There will be administrative disadvantages. This is the trade-off.
vSIE (the thing invoked when the 2nd level system issues a SIE instruction to dispatch a 3rd-level guest) is slower than the real SIE instruction.
Further the SIE instruction the 1st level VM system ultimately issues on behalf of that 3rd-level guest has so many provisos, advisories, and limits, that it will exit at the slightest provocation. And the time slice for a 3rd-level guest is a fraction of the 2nd level time slice. The 3rd level guest just doesn't typically get to spend much quality time alone with the CPU (relative to all that's happening in the 1st level system).
You can see, I hope, why it can be difficult to maintain production performance levels for 3rd level guests. You can do it, but it's labor and resource intensive. For development, testing, and QA, 2nd level VM systems are the bee's knees, but my preference is to put production VM systems in LPARs. The z9 EC has 60 LPARs, in case you were wondering. Do you want one? I know people.....
And because this is a discussion about performance, my attorney advices the following disclaimers:
- It depends(sm)
- YMMV
:-)
Alan Altmark
z/VM Development
IBM Endicott
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