Re: [Xen-users] Is NPTL in PV Xen Possible in RHEL5/CentOS 5 Distros?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I'm in a bit of a bind.  My organization is planning to move to a new
> mail system and I really want this box to be up as close to 24x7 as
> possible.  I am currently working on an HVM domain running RHEL on top
> of CentOS.  What I'm concerned about is the issue of I/O (disk and
> network) since a mail system will be very busy in that way.  The mail
> app I'm planning on running needs NPTL.  When I tried a paravirtualized
> Fedora Core a few years back, the installer for that app said it
> wouldn't install since the kernel didn't have NPTL.  So this led me to
> believe that I had to wait for HVM.

You're right that HVM ought to work for you.

> Now, I'm not so sure...  In my 
> recent searches, I've seen that all that's really required is a glibc
> that supports NPTL and that if one runs Xen this way, you wind up with
> slow performance.  I suspect this has something to do with the TLS lib
> that many Xen docs say to rename?

In the olden days, if you didn't rename the TLS lib (to disable it) then Xen 
would have to do a whole load of emulation.  Ought to be correct, but would 
cause some slowdown.

RHEL5 and CentOS 5 ship a glibc setup which is Xen aware and will do the Right 
Thing when used on a Xenified kernel.  It should Just Work for you.

>
> So has anyone made a glibc that will install on RHEL or CentOS that is
> Xen friendly at this point?  If so, I may be in much better shape than I
> thought.

RHEL and CentOS ship with Xen.  The glibc they ship ought to work (at least, 
it ought to work with their kernels, and I assume it'll work with others) 
with good performance and without you having to make any manual configuration 
changes.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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