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

[Andrew Ross <aross@xxxxxxxxxx>]

Angel de Vicente wrote:

>  > > until now I have run Xen with /lib/tls out of the way for both dom0 and 
> domU's,
>  > > but now I'm trying to install OpenLDAP in a domU, which requires TLS as
>  > > default. So now I have at least three options ahead of me:
>  > 
>  > I doubt, those two TLSs are the same:
>  > 
>  >  TLS[OpenLDAP]: Transport Layer Security
>  >  TLS[!XEN]: Transaction Local Storage
>  >  
>  > You can safely compile openldap with tls.
> 
> Ah, OK, I got confused about this (never compiled OpenLDAP before). So I guess
> from my original post then I only get the first and the third options left
> (i.e. either to restore /lib/tls or to get a xen-friendly glibc). The first
> option works OK (as can seen below), but I guess the customary warning on
> performance. I will try a xen-friendly glibc as well, but I wonder if anyone 
> can
> shed some light on what the performance hit will be?

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.

Cheers

Andrew Ross

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