Hi, Terry.
z/VM is built to do "a lot of paging"....:-) Are you having a performance problem of some
sort that you suspect might be related to paging? Or are the paging rates larger than you
feel comfortable with? You did specify any actual numbers, but it's not unusual for a
large z/VM system to page at several thousand pages a second.
Any good VM performance monitor (Velocity, PerfKit) can tell you which guests are paging
and by how much. You'll need one of those if you suspect that you do indeed have a
performance problem related to paging. If you are interested in seeing which specific
Linux process, running inside a Linux virtual machine, is causing the paging, you're going
to have to use some tools that understand how Linux manages it's virtual memory, and
that's another issue.
CP can make very effective use of expanded storage as a page cache area. You do have some
of the memory in the z/VM LPAR defined as expanded storage, right?
Kris Buelens wrote:
As for the selection of "good old data" to be thrown out by CP:
- Linux can tell CP that it no longer needs certain storage pages
using a diagnose code. If it does ???
- CRM 2 is a Linux/CP co-operative feature by which CP would know what
kind of data resides in which Linux pages. For example: if CP knows a
page is used to cache disk data, it doesn't need to page it out, Linux
can read it back in from its disks.
- Apart from that, CP's selection of candidates to page out from
central storage is not as clever is in z/OS: it only uses the last
reference bit. That is why a z/VM installation would be configured
with some amount of expanded storage, because there is a timestamp for
each expanded storage page that allows CP to select old pages for
pageout.
2009/2/10 Barton Robinson <[email protected]>:
In ESALPS, ESAUSPG shows by user. ESAUCD2 shows if you have extra cache or
buffer. If you can send your reports, we will analyze it at no charge.
Martin, Terry R. (CMS/CTR) (CTR) wrote:
Hi
I seem to be doing a lot of paging currently on my z/VM 5.3 system I am
running multiple Linux guests including a large Oracle guest (40 GB memory
size). How can I find out 1) who is doing the majority of the paging and
along with that 2) I believe that some of the paging slots are old data in
other words the pages are not going away after a task is complete how can I
research this. The Linux guests have not been recycled but I thought if they
had allocated the slots that after a task within the Linux guest completed
that the slots would be reclaimed. Any thoughts on all of this would be
appreciated.
//Thank You,//
//Terry Martin//
//Lockheed Martin - Information Technology//
//z/OS & z/VM Systems - Performance and Tuning//
//Cell - 443 632-4191//
//Work - 410 786-0386//
//[email protected] <mailto:[email protected]>//
--
DJ
V/Soft
z/VM and mainframe Linux expertise, training,
consulting, and software development
www.vsoft-software.com
