virt May 2011

virt@lists.centos.org

14 participants
12 discussions

Re: [CentOS-virt] A question about memory ballooning
by carlopmart 07 May '11

07 May '11

> And the opposite question, can memory balloon be deallocated?? And is > it possible to do this automatically or is an error to do this?? I think your understanding of ballooning may be backwards. The purpose of the balloon driver is to give the host system a way of recovering memory from the guest when the demands on the host's physical memory exceed the amount available. The balloon inflates within the guests forcing them to swap or take other memory management measures. When the pressure on the host eases the balloon deflates automatically. Sorry Drew, but I don't understand the use of balloon driver like you explains. According to RedHat's docs: "The balloon driver allows guests to express to the hypervisor how much memory they require. The balloon driver allows the host to efficiently allocate memory to the guest and allow free memory to be allocated to other guests and processes. Guests using the balloon driver can mark sections of the guest's RAM as not in use (balloon inflation). The hypervisor can free the memory and use the memory for other host processes or other guests on that host. When the guest requires the freed memory again, the hypervisor can reallocate RAM to the guest (balloon deflation). " http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualiz… (The balloon driver) I don't see in this doc any reference to "balloon driver is to give the host system a way of recovering memory from the guest when the demands on the host's physical memory exceed the amount available" -- CL Martinez carlopmart {at} gmail {d0t} com

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Package updates and "required" reboots
by Ben M. 06 May '11

06 May '11

I still operate under the assumption that glibc and kernel updates "require" a reboot to be prudent on a Linux OS. With CentOS Xen 5.6 (standard installation, SELinux enabled) is there an FAQ or general user consensus as to when to do a reboot after what updates?

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virt May 2011