We just ipled a new VM4.3 cp load module to install VM63282. We currently have 7 Linux guests (SLES8 Kernel 2.4.19-3suse-SMP (ttyS0)) that are always in Q3. After VM63282, they are still in Q3. No change. I noticed that Bill mentioned a timer patch for the Linux guests. Is this included in the Service Pack 2 for the SuSE Linux Enterprise Server 8 for IBM Mainframes? Where can I direct our Linux sysadmins to get this patch, and will it allow the guests to go idle and drop out of Q3?
The modern kernels like you get in SLES8 includes the timer patch but it is not enable by default. In these kernels you have /proc/sys/kernel/hz_timer that you can 'cat' to display the current setting. I expect you see a '1' there. An 'echo 0 > /proc/sys/kernel/hz_timer' should make a difference for you.
If it still does not, you could follow the recipe from the Performance and Tuning Redbook to determine which process is asking for frequent wakeup, if any.
We are about to bring up 100+ Linux guests for student use, but are concerned about the Q3 problem and its implications. Should we be worried about the Linux guests staying in Q3?
I would be worried. Obviously it depends, among others on the amount of storage and the size of the virtual machines, and on the level of z/VM. You may even need to educate the students (is that possible?) not to waste the resources.
Rob
