On Wed, Aug 14, 2013 at 12:18:41PM +0700, Pandu Poluan wrote: > 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.
To check what options CFLAGS set as -march=native would use: gcc -march=native -E -v - </dev/null 2>&1 | sed -n 's/.* -v - //p' (the first thing in the output is what CPU -march=native would enable) Then you can run: diff -u <(gcc -Q --help=target) <(gcc -march=native -Q --help=target) to display target-specific options, versus native ones. Assuming the 2 HP servers are identical, and the 5 Dell servers are identical, you then only need to get the commonality of two processors (HP and Dell). Since they're both AMD, you should have a good set of common features to help you determine that "least common denominator", or target. -- Happy Penguin Computers >') 126 Fenco Drive ( \ Tupelo, MS 38801 ^^ supp...@happypenguincomputers.com 662-269-2706 662-205-6424 http://happypenguincomputers.com/ A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? Don't top-post: http://en.wikipedia.org/wiki/Top_post#Top-posting
