>>> On Fri, Sep 14, 2007 at 6:48 AM, in message <[EMAIL PROTECTED]>, "Evans, Kevin R" <[EMAIL PROTECTED]> wrote: > Rob, > > As we are just switching to Omegamon and almost up to implementation of > our first user to come into a new zLinux front end, can you give ant > further details on your comment below?
Prior to the kernels used in SLES10 and RHEL5, the way CPU consumption was tracked by the Linux kernel didn't take into account that the system may be running in a shared/virtualized environment. The (valid until LPARs, z/VM, VMware, and Xen) assumption in place was that the kernel was in complete control of the hardware, so any passage of time between the last clock value taken, and the current one, was assigned to whatever process was dispatched in the interval. The problem being, of course, that the virtual machine/LPAR might not have been running at all during that time. So, Linux could report that the CPU was 100% busy, when in fact it was only being dispatched, for example, 3% of the time. Of the various performance monitors that were being marketed for mainframe Linux, only Velocity Software's product combined the Linux data with the z/VM monitor data, and normalized the Linux values to be correct. (Obviously this only worked in an environment where z/VM was being used as the hypervisor.) This was a big factor in many cases of which monitor to choose. Since the release of the "cpu accounting" patches, and incorporation into SLES and RHEL, that's no longer the case, unless you're still running SLES8 (Hi, Marcy!) and SLES9 (Hi, almost everyone else!), or RHEL3 or 4. Now the decision is based on more traditional criteria, as opposed to being right or very wrong. If you have a userid and password to access the SHARE proceedings, you can see Martin Schwidefsky's presentation on this at http://www.share.org/member_center/open_document.cfm?document=proceedings/SHARE_in_Seattle/S9266XX172938.pdf (I have no idea why I didn't ask Martin for a copy of that for the linuxvm.org web site. Rats.) Mark Post ---------------------------------------------------------------------- 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
