That seems to be the opposite of what USAGE NOTE 6 states for HELP CPSE
SHARE:
"When setting SHARE RELATIVE on a userid that has multiple CPUs, the
minimum share that the system will assign is one per virtual CPU. For
example, if you SET SHARE MAINT RELATIVE 1 and MAINT has five virtual
CPUs, the resulting SHARE will be set to five."
By the above, setting RELATIVE 100 with 2 CPUs you get an effective
RELATIVE 200.
-----Original Message-----
From: The IBM z/VM Operating System
[mailto:[EMAIL PROTECTED] On Behalf Of Schuh, Richard
Sent: Friday, March 23, 2007 2:59 PM
To: [email protected]
Subject: Re: CPU usage -- virtual or dedicated ?
The Relative 100 applies to the overall virtual machine. If you
define each with 2 cpus, each cpu would be competing at a Relative 50
when the system is busy. That may be an inhibiting factor. With our TPF
systems, each normally running with 3 CPUs - sometimes more, sometimes
fewer, we multiply the number of cpus by 100 to arrive at a relative
share value for the virtual machine. This seems to solve a lot of
slowdown issues that our testers encounter.
Regards,
Richard Schuh
_____
From: The IBM z/VM Operating System
[mailto:[EMAIL PROTECTED] On Behalf Of Kris Buelens
Sent: Friday, March 23, 2007 11:41 AM
To: [email protected]
Subject: Re: CPU usage -- virtual or dedicated ?
As the first share setting is "REL 100" they get the same
priority as any other VM user that wants to run.
So, if you want to give them a favor you should e.g. set the
first share to REL 1000, or maybe ABS 30%
2007/3/23, Stracka, James (GTI) <[EMAIL PROTECTED]>:
I am not in favor of dedicating virtual CPUs as this restricts
the other
users of the system and is a potential waste of resources and
money.
Since the CP Scheduler does an excellent job of distribution of
the
resources, then using the SHARE command might be better.
Assuming there are more than two VSE machines of which two
really need
to use two virtual CPUs each and there are four real CPUs, then
if I am
correct issue two SET SHARE commands:
set share vseguest1 relative 100 absolute 49% limithard
set share vseguest2 relative 100 absolute 49% limithard
Okay, it could be absolute 50% but if both VSE guests wanted the
maximum
resources at the same time, no other work would get done.
My understanding of those two commands is that they would allow
either
VSE guest to get almost the full usage of two real CPUs each any
time
they need them. Stated another way, either could at most get
49% of the
box leaving the remaining 51% for all the other users of the
four CPUs.
If both wanted the maximum at the same time it would be 49% for
vseguest1, 49% for vseguest2 and 2% for the remaining users.
Any other
time, the workload would be spread evenly among all the guests
in the
box given QUICKDSP and other SHARE settings.
Am I correct?
--
Kris Buelens,
IBM Belgium, VM customer support
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