Would IBM care to comment to this group concerning CMMA? I am about to embark on a benchmark of CMM and CMMA. During my initial playing with setup of CMM and CMMA, I have found CMMA to be much easier. Being lazy I like the Ronco oven approach ( sorry if you don't watch infomercials) of "set it and forget it". I too want performance data so don't misinterpret the previous sentence. I like the idea of linux checking/setting extended hardware bits and then DIAG 10 RELPAGing. CMMA is just CMS on steroids. With the ballooning approach of CMM there is more work to do, plus I wouldn't rush into using production servers on the shared memory pool. I want favored nation status for production servers. Something appeals to me about the intrinsic nature of having the kernel decide which page to DIAG 10 when CMMA is used. I realize that there are implications of doing this for System z far beyond our mainframe shores but frankly I don't care. We need all the help we can get managing our expensive memory plus we have to deal with our naughty WAS children that never drop from queue. I'm expecting big things from CMM and/or CMMA. David Kreuter
________________________________ From: Linux on 390 Port on behalf of Rob van der Heij Sent: Wed 12/17/2008 11:16 AM To: [email protected] Subject: Re: Over Committing Storage in z/VM 2008/12/17 ???? ???? <[email protected]>: > Anyone here using CMM for over committing? It sounds great! is it working > great as well? It's so great there are even two of them ;-) CMM-1 (also called ballooning) is to temporarily take away memory from Linux when it should not be using it. Can be used if you understand the application requirements in Linux, for example with a TSM backup that should have memory over night but not during daytime. Or when you have an external process that can take VM performance data and decide how much Linux can have or needs. CMM-2 (or CMMA - requires adequate hardware and software) This is supposed to happen all automatic with no tuning options and no instrumentation on what it does... Current software levels don't enable it per default, and future levels may not include the full feature anymore. For CMMA, I used to say "It is a very cool research item. In lab environment, an artificial workload could be constructed that takes advantage of it." Any performance data I have seen from IBM confirms this status. And for completeness, there is CMM-0 ;-) Make sure your virtual machines drop from queue when idle, so z/VM can do memory management. Tune the ratio between high-performance swap and virtual machine memory based on the workload characteristics and business justification (so a test server has higher latency and lower cost). Look for my post on Nov 27th: www.mail-archive.com/[email protected]/msg50668.html (Google found it searching for ""real disks for swap is only good for slowing down Linux") Rob Rob van der Heij Velocity Software http://www.velocitysoftware.com/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
