Xen users - Mar 2006 - how to find out whether glibc is XEN-ready or not

According to their instructions the glibc coming with SuSE 10.0 should 
be patched in a way that /lib/tls can be used. I enabled /lib/tls again 
and it worked - but how can I be sure that xen is really running in an 
efficient mode not using wrap-around segments?

regards,
ulf behrens

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On Fri, Mar 31, 2006 at 05:49:41PM +0200, Ulf Behrens wrote:
> According to their instructions the glibc coming with SuSE 10.0 should 
> be patched in a way that /lib/tls can be used.
  I''ve had problems compiling and running some application with TLS
enabled
  (in dom0; domU was OK) - it just hung (somewhere in syscall). The problem
  was reproducible. Disabling tls solved this issue.
  
Regards,
/Al

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> I can''t speak for the SuSE package, but on FC5 glibc picks up the
right
> TLS version automatically too.  You can check it''s working with
>
> 	$ cat /proc/self/maps
>
> which on my local i386 dom0 shows:
>
>                 /lib/i686/nosegneg/libc-2.4.so
>
> as the libc in use, showing it is detecting and using the
"nosegneg"
> Xen-friendly version automatically.  SuSE may well be using a similar
> scheme.
IIRC, SuSE''s TLS just never uses negative segment references, even on
native -
I understood they didn''t find the performance advantages justified the
extra
complexity switching for Xen-vs-native.

Cheers,
Mark

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Hi,

On Fri, 2006-03-31 at 17:49 +0200, Ulf Behrens wrote:
> According to their instructions the glibc coming with SuSE 10.0 should 
> be patched in a way that /lib/tls can be used. I enabled /lib/tls again 
> and it worked - but how can I be sure that xen is really running in an 
> efficient mode not using wrap-around segments?
I can''t speak for the SuSE package, but on FC5 glibc picks up the right
TLS version automatically too.  You can check it''s working with

	$ cat /proc/self/maps

which on my local i386 dom0 shows:

                /lib/i686/nosegneg/libc-2.4.so

as the libc in use, showing it is detecting and using the "nosegneg"
Xen-friendly version automatically.  SuSE may well be using a similar
scheme.

--Stephen



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