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Re: [Xen-users] /lib/tls.disabled or xen-friendly glibc?

To: Andrew Ross <aross@xxxxxxxxxx>
Subject: Re: [Xen-users] /lib/tls.disabled or xen-friendly glibc?
From: Angel de Vicente <angelv@xxxxxx>
Date: Tue, 29 Aug 2006 09:55:42 +0100
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Hi Andrew,

Andrew Ross writes:
 > I recall reading that the performance hit from using a Xen-friendly
 > glibc (ie. one compiled with the -mno-tls-direct-seg-refs CFLAG) over a
 > regular TLS-enabled glibc is less than the performance penalty of having
 > Xen emulate the TLS negative segment offsets, and presumably also less
 > than the performance penalty of using LinuxThreads instead of TLS.
 > 
 > Thus, it would be my recommendation that you switch to a Xen-friendly
 > glibc - you haven't mentioned your distribution, but I'll assume it's
 > not Gentoo.

Thanks for the tip. No, my distribution(s) are not Gentoo. I use Ubuntu 5.10 as
dom0 and CentOS4.3 as domU. Now, for the domU's I have a precompiled
xen-friendly glibc which I have already used, but not so for Ubuntu. So, my next
question was whether it makes any sense to have TLS disabled/"unfriendly glibc"
in dom0 and TLS enabled/xen-friendly glibc in domU. Would domU benefit or would
I have to have a xen-friendly glibc in dom0 as well?

Any suggestions on what benchmarks would be useful to test this? I would gladly
perform them and report back to the list (time permitting, of course)...

Cheers,
Ángel de Vicente
-- 
----------------------------------
http://www.iac.es/galeria/angelv/

PostDoc Software Support
Instituto de Astrofisica de Canarias


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