That would be a useful capability, especially for those of us who cannot
spend the resources (LPAR Profile changes, deactivation/activation of
LPAR, etc.) to fine tune the ratio of main to expanded storage. Being
able to tweak a value in the SYSTEM CONFIG or, better yet, dynamically
at IPL time would be nice. I presume that making all memory main storage
and setting aside some amount to use as the intermediate buffer would
not be too onerous a task. One benefit that would accrue from doing so
would be that pages could be written directly from the buffer. There
would be no need to move them to main storage before writing them. This
could be a good thing, lessening the time and overhead to perform the
page-out.
Regards,
Richard Schuh
________________________________
From: The IBM z/VM Operating System
[mailto:[email protected]] On Behalf Of James Stracka (DHL US)
Sent: Thursday, March 05, 2009 6:58 AM
To: [email protected]
Subject: Re: XSTORE
I agree. Then we would not have to reconfigure LPAR storage
definitions when testing OS/390 and z/VM.
________________________________
From: The IBM z/VM Operating System
[mailto:[email protected]] On Behalf Of Huegel, Thomas
Sent: Wednesday, March 04, 2009 4:05 PM
To: [email protected]
Subject: Re: XSTORE
Understanding that CP uses an algorithm that handles XSTORE as a
preferred paging area the question arises as to why?
Since XSTORE is just a piece of main memory the reason for it's
existence is no longer that it is some cheaper slower memory that can be
used for paging.
I think we all look at setting up the hardware and defining
XSTORE as a permanent definition.
Is it time to change CP, perhaps adding a parm to SYSTEM CONFIG
that says OK CP use 500 meg of main storage for paging etc.? In other
words instead of making a hard configuration change lets just tell CP
how much memory to 'treat' as XSTORE.
-----Original Message-----
From: The IBM z/VM Operating System
[mailto:[email protected]]on Behalf Of Kris Buelens
Sent: Wednesday, March 04, 2009 1:43 PM
To: [email protected]
Subject: Re: XSTORE
Attaching XSTORE to a user: you can, but it is up to the
user to do something with it, CMS doesn't use it at all, z/OS no longer
supports it, and I don't know about Linux.
To define some XSTORE fo CP is still a good thing if VM
starts paging: XSTORE is managed differently than central storage. With
some XSTORE CP has a better chance to select the best pages to page out.
2009/3/4, Michael Coffin <[email protected]>:
Hi Folks,
What value is there in defining XSTORE these days?
Aside from the ability to attach XSTORE to specific virtual machines,
wouldn't it be best to just make it all DPA and let CP manage it?
Also, assuming you aren't paging much - is attaching
XSTORE to a userid going to provide a VERY noticable improvement in
performance (at the expense of taking it away from all other virtual
machines, of course)?
-Mike
--
Kris Buelens,
IBM Belgium, VM customer support
