Less RAM in VM than allocated RAM on host

aslbhr

Hi ,

I have installed "Oracle Linux Server release 7.9" as guest by allocating 8GB RAM

When i logged into VM, i see that fewer memory is available

[root@oelrac01n01 etc]#  grep MemTotal /proc/meminfo
MemTotal:        7839920 kB

param list on host is following

[15:43 xcp-ng-duexgxtk etc]#  xe vm-param-list uuid=1fb2e6c5-6210-92ca-f547-e1c9bbac5596| grep memory
                         memory-actual ( RO): 8589934592
                         memory-target ( RO): 0
                       memory-overhead ( RO): 77594624
                     memory-static-max ( RW): 8589934592
                    memory-dynamic-max ( RW): 8589934592
                    memory-dynamic-min ( RW): 8589934592
                     memory-static-min ( RW): 134217728
                       recommendations ( RO): <restrictions><restriction field="memory-static-max" max="137438953472"/><restriction field="vcpus-max" max="32"/><restriction field="has-vendor-device" value="false"/><restriction field="supports-bios" value="yes"/><restriction field="supports-uefi" value="yes"/><restriction field="supports-secure-boot" value="yes"/><restriction max="255" property="number-of-vbds"/><restriction max="7" property="number-of-vifs"/></restrictions>
                                memory (MRO):

any idea why i have fewer memory in VM?

olivierlambert

That memory is needed because of:

shadow copies of page tables, needed during migration or if hardware assisted paging is not available
video RAM for the virtual graphics card
records in the hypervisor describing the VM and the vCPUs

olivierlambert

Because you have 74MiB of memory overhead, as visible in memory-overhead value.

aslbhr

Hi Oliver ,

Thank you for answer. What is memory-overhead and why it is 74 Mib

olivierlambert

That memory is needed because of:

shadow copies of page tables, needed during migration or if hardware assisted paging is not available
video RAM for the virtual graphics card
records in the hypervisor describing the VM and the vCPUs

aslbhr

This post is deleted!

aslbhr

can video RAM for the virtual graphics card be set /decreased ?

Thank you.

olivierlambert

Check the Advanced tab of the VM

aslbhr

which one ?

olivierlambert

In Xen Orchestra, XCP-ng Center isn't a supported client for XCP-ng.