Hello Dave,
In either case, if a linux (zlinux or intel) gets 768M it will
eventually allocate all storage it can get. If not for applications it
will use the 'free' memory for datacache. So in that repect, yes, the
linux will use the storage you assign to the guest. But as for if the
image really needs the storage, that will depend on the application you
are running in the guest. In some cases you really need the storage but
some applications offer the requirements to be set. Oracle for example
can set buffersizes.
I always try to convince the linux and/or application owners to request
less storage for their linux image. Try, but not always successfull. Our
zLinux machines run from 200M up to about 6000M. The first are small
machines such as installation and SSL, the latter are large oracle
machines. We run the linux images in two VM's of 10G each.
At least you're not the only one who has seen this. We also have found
the situation where we over allocated the VM image. That's not bad, in
fact it is our unique selling point, but if SRM is not set accordingly
you'll find guests in the E-list and start to wonder why a guest will
stop processing. Evaluate your LDUBUF and STORBUF and also make sure you
will have enough page space to hold all of your (vitual) storage needs.
Regards, Berry.
O'Brien, David W. (NIH/CIT) [C] schreef:
Thanks John
cp q srm
IABIAS : INTENSITY=90%; DURATION=2
LDUBUF : Q1=100% Q2=75% Q3=60%
STORBUF: Q1=300% Q2=200% Q3=200%
DSPBUF : Q1=32767 Q2=32767 Q3=32767
DISPATCHING MINOR TIMESLICE = 5 MS
MAXWSS : LIMIT=9999%
...... : PAGES=999999
XSTORE : 0%
Just got the following from one of the other techs (non-VM)
We were able to diagnose the problem and make the necessary correction.
The problem was z/VM has a total 768m of central available. The Linux guests (3
total) each had 768m of central allocated, therefore contention.
The Linux guests are over allocated and are storage constrained with 768m of
central.
Understanding the Linux guests would be in contention with each other for this
storage VM time sliced what it could for each
guest, therefore the symptoms we experienced.
My question to this group - Does a Linux quest really require 768MB of Central?
Regards,
Dave O'Brien
________________________________
From: Romanowski, John (OFT) [mailto:[EMAIL PROTECTED]
Sent: Thu 3/20/2008 1:45 PM
To: IBMVM@LISTSERV.UARK.EDU
Subject: Re: Performance problem Linux under Zvm
If CP INDICATE QUEUES shows an En (like E3)
in the 2nd column for one or more userids
try CP QUERY SRM (write down response for reviewing )
and do this quick fix
CP SET SRM STORBUF 300% 300% 300%
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-----Original Message-----
From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On
Behalf Of O'Brien, David W. (NIH/CIT) [C]
Sent: Thursday, March 20, 2008 1:37 PM
To: IBMVM@LISTSERV.UARK.EDU
Subject: Performance problem Linux under Zvm
Our shop is new to Zvm and Linux. We have a very small number of Linux
users who are reporting significant response time problems. It almost
seems as if each stops running for a period of time and is then
re-dispatched.
Is there a VM parameter that we might have taken the default on that
needs tweaking?
Any help or advice appreciated as this is a proof of concept endeavour
and we would like not to turn off prospective users from the start.
Thank you,
Dave O'Brien
National Institutes of Health
