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[Xen-users] When should I use '-mno-tls-direct-seg-refs' ?

To: Xen-Users <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-users] When should I use '-mno-tls-direct-seg-refs' ?
From: Pandu Poluan <pandu@xxxxxxxxxxx>
Date: Mon, 13 Jun 2011 13:56:47 +0700
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Hello list!

I'm trying to create a VM (Gentoo x86) on an x86_64 platform, but will
later be migrated to a Pentium4 platform.

When I was compiling glibc on the VM, I got the following warning
(please excuse the Gentoo-ism, if any):

 * You are using Xen but don't have -mno-tls-direct-seg-refs in your CFLAGS.
 * This will result in a 50% performance penalty when running with a 32bit
 * hypervisor, which is probably not what you want.

I'm not really sure what that means, or what I'm supposed to do. So
I'll really appreciate your confirmation of my thoughts:

1. If I want to run Gentoo x86 on a 32-bit platform (i.e., Pentium4
physical processor), I need -mno-tls-direct-seg-refs in my CFLAGS

2. If I want to run Gentoo x86 on a 64-bit platform, I don't need
-mno-tls-direct-seg-refs

3. If I want to run Gentoo amd64 on a 64-bit platform, the
-mno-tls-direct-seg-refs arg is not relevant

Am I getting those right?


TIA for your assistance.

Rgds,

-- 
Pandu E Poluan
~ IT Optimizer ~
Visit my Blog: http://pepoluan.posterous.com
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