Belkin XM Commander Manuel d'utilisateur télécharger pdf (Page 26)

4.4 Managing Domain Memory

XenLinux domains have the ability to relinquish / reclaim machine memory at the

request of the administrator or the user of the domain.

4.4.1 Setting memory footprints from dom0

The machine administrator can request that a domain alter its memory footprint using

the xm set-mem command. For instance, we can request that our example ttylinux

domain reduce its memory footprint to 32 megabytes.

# xm set-mem ttylinux 32

We can now see the result of this in the output of xm list:

# xm list

Name Id Mem(MB) CPU State Time(s) Console

Domain-0 0 251 0 r---- 172.2

ttylinux 5 31 0 -b--- 4.3 9605

The domain has responded to the request by returning memory to Xen. We can restore

the domain to its original size using the command line:

# xm set-mem ttylinux 64

4.4.2 Setting memory footprints from within a domain

The virtual ﬁle /proc/xen/balloon allows the owner of a domain to adjust their

own memory footprint. Reading the ﬁle (e.g. cat /proc/xen/balloon) prints out

the current memory footprint of the domain. Writing the ﬁle (e.g. echo new target

> /proc/xen/balloon) requests that the kernel adjust the domain’s memory foot-

print to a new value.

4.4.3 Setting memory limits

Xen associates a memory size limit with each domain. By default, this is the amount

of memory the domain is originally started with, preventing the domain from ever

growing beyond this size. To permit a domain to grow beyond its original allocation

or to prevent a domain you’ve shrunk from reclaiming the memory it relinquished, use

the xm maxmem command.

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Belkin XM Commander Manuel d'utilisateur Page 26