OK, now you confused me. By virtue of the fact that it has 2 VCPUs in
an 11 RCPU environment, would it not automatically be capped at 18.18%
because it cannot get more than two CPUs?
Or, did you mean 2.5% and not 25%?
-----Original Message-----
From: The IBM z/VM Operating System
[mailto:[EMAIL PROTECTED] On Behalf Of James Vincent
Sent: Friday, August 03, 2007 9:08 PM
To: [email protected]
Subject: Re: SET SHARE RELATIVE
I certainly did not want to cause confusion - this is why I said
" There is actually more science..." I was passing on what we learned
through trial, error and then a phone call. And blast it, you are
indeed correct Kris.
On a system with 11 IFLs and a 2 vcpu guest that we needed to
cap at 25%, we had to set its share as SET SHARE RELATIVE 200 ABSOLUTE
2.3% LIMITHARD. This is the only way we could successfully get the
server to not go over 25% cpu total.
In our case, the linux guests are all multi-processor apps and
none are multi-vcpu uniprocessor apps so the behavior was as expected,
the apps got up to 25% (and not 12.5% if they were uniprocessing)
The answer is I guess "It Depends" since you will really need to
know your applications and how they run in order to set the SHARE the
way you really need it. I was trying to keep it "simple" - ha!
Jim
On 8/3/07, Kris Buelens <[EMAIL PROTECTED]> wrote:
Jim, I'd say your append can introduce confusion.
The vcpus still count for absolute shares. But, indeed,
the number of real CPUs come into account: the % written on the SET
SHAER command is expressed as a % of the whole system.
If you have 10 CPU's, a SET SHARE ABS 5% LIMITHARD means
that a uniprocessor guest can consume 50% of one CPU. If the guest has
two virtual processors, each one can consume 25% at most. This is very
important if this guest would run one heavy uniprocessing task, this
task will have a hard time to get more than 25% of a CPU. We learned
this the hard way when installing a 6 engine 9672 ages ago (our heavy
process was a VM DB2 server)
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