Xen users - Mar 2006 - /lib/tls.disable vs. software requiring tls

On Monday 13 March 2006 18:05, Mathias Diehl wrote:
> Hi List,
>
> maybe a very stupid question - but according to the xen developers you
> shoudl disable tls. Beeing not that familiar with this stuff I would like
> to know who software will work that requires tls... (like
MTA''s...)
>
> thanx for a short reply

I think you confused TLS (Thread Local Storage, a technique to implement 
per-thread data) with TLS (Transport Layer Security, a encryption technique 
on TCP-Sockets).

in short, your MTA won''t be affected.

/Ernst

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Hi List,

maybe a very stupid question - but according to the xen developers you shoudl
disable tls. Beeing not that familiar with this stuff I would like to know who
software will work that requires tls... (like MTA''s...)

thanx for a short reply

mat

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On Tuesday 14 March 2006 20:11, you wrote:
> Hi,
>
> but what about tomcat ? I use jre (java binary) which is linked to tls
> (thread local storage) :
>
> ldd /opt/jre/bin/java
>          linux-gate.so.1 =>  (0xffffe000)
>          libpthread.so.0 => /lib/tls/libpthread.so.0 (0xb7f34000)
>          libdl.so.2 => /lib/tls/libdl.so.2 (0xb7f30000)
>          libc.so.6 => /lib/tls/libc.so.6 (0xb7df9000)
>          /lib/ld-linux.so.2 (0xb7f4b000)
>
> when i start a tomcat instance in a xen domU, i get lot of processes
> instead a single (but multi-threaded) process ?
>
Thats because in the old thread library each thread got its own process ID, 
the kernel had only little support for threads, so it had to be done that 
way.
(With nptl, they still have an own PID, but its hidden from the userspace 
better)

Without xen, nptl provides a huge speed boost to threaded applications (esp 
Java), so you really should try to get a xen-compilant NPTL glibc running.
=> no speed loss from xen emulating TLS, but all the benefits from futexes, 
fast context switch between threads, ...

So, moving /lib/tls away is just a quick workarround, installing a
"fixed"
glibc is a solution.

/Ernst

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Ernst Bachmann wrote:
> On Tuesday 14 March 2006 20:11, you wrote:
>> Hi,
>>
>> but what about tomcat ? I use jre (java binary) which is linked to tls
>> (thread local storage) :
>>
>> ldd /opt/jre/bin/java
>>          linux-gate.so.1 =>  (0xffffe000)
>>          libpthread.so.0 => /lib/tls/libpthread.so.0 (0xb7f34000)
>>          libdl.so.2 => /lib/tls/libdl.so.2 (0xb7f30000)
>>          libc.so.6 => /lib/tls/libc.so.6 (0xb7df9000)
>>          /lib/ld-linux.so.2 (0xb7f4b000)
>>
>> when i start a tomcat instance in a xen domU, i get lot of processes
>> instead a single (but multi-threaded) process ?
>>
> Thats because in the old thread library each thread got its own process ID,
> the kernel had only little support for threads, so it had to be done that 
> way.
> (With nptl, they still have an own PID, but its hidden from the userspace 
> better)
> 
> Without xen, nptl provides a huge speed boost to threaded applications (esp
> Java), so you really should try to get a xen-compilant NPTL glibc running.
> => no speed loss from xen emulating TLS, but all the benefits from
futexes,
> fast context switch between threads, ...
> 
> So, moving /lib/tls away is just a quick workarround, installing a
"fixed"
> glibc is a solution.
> 
> /Ernst
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
Thanks for your answer Ernst,

Do you know where could i get a fixed glibc ? any project ?


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