[CentOS-virt] kvm guest ram

Tue May 24 13:53:59 UTC 2011
Markus Falb <markus.falb at fasel.at>


On a 4gb 64 bit centos kvm guest per libvirt


but in dmesg of the guest I find

Memory: 4039712k/5242880k available (2592k kernel code, 154076k
reserved, 1653k data, 224k init)

Why is dmesg reporting 5g of ram ? Or am I reading wrong ?
How much memory on the Host is necessary on the kvm host for this "4g"
machine in the worst case (I try to not overcommit for now). I want to
avoid the situation that this "4g" machine requires "5g".

A 4gb 32 bit machine is reporting expected values

Memory: 3102712k/4194304k available (2190k kernel code, 41592k reserved,
911k data, 228k init, 2228160k highmem)

All of the above lead to the following more generic question:
How many percent of the Host RAM may I safely give to guests (without
overcommiting) ?

Kind Regards, Markus Falb

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