[gentoo-user] How to determine 'Least Common Denominator' between Xen(Server) Hosts

[Pandu Poluan]

Hello list!

My company has 2 HP DL585 G5 servers and 5 Dell R... something servers. All
using AMD processors. They currently are acting as XenServer hosts.

How do I determine the 'least common denominator' for Gentoo VMs (running
as XenServer guests), especially for gcc flags?

I know that the (theoretical) best performance is to use -march=native ,
but since the processors of the HP servers are not exactly the same as the
Dell's, I'm concerned that compiling with -march=native will render the VMs
unable to migrate between the different hosts.

Note: Yes I know the HP servers are much older than the Dell ones, but if I
go -march=native then perform an emerge when the guest is on the Dell host,
the guest VM might not be able to migrate to the older HPs.

Rgds,
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