[Xen-ia64-devel] Re: SMP patch

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Jeudi 13 Octobre 2005 14:56, Magenheimer, Dan (HP Labs Fort Collins) a 
écrit :
> > > 2) Is there a reason you reduced the VHPT size 4x?  It
> > >    appears to have slowed performance down noticably
> > >    (about 1%).
> >
> > I tried to boot with 6 procs, and the boot failed because the
> > xenheap is to
> > small.  Please, restore the VHPT size.
>
> I see.  The early physical memory allocation for Xen was
> written long ago and is probably still very primitive and
> restrictive. It definitely needs some work to handle
> new demands such as more CPUs and more domains.
>
> It would be useful to understand how much physical memory
> is needed per processor (and also per domain).  Shrinking
> the VHPT is just a short-term solution; you will just run
> out of xenheap when you add a few more processors, correct?
Yes, this is correct.
I will try to figure out how much memory is required per proc and per domain.

> Perhaps a better short-term solution (than hard-coding a
> smaller VHPT) would be to use a xen command-line flag
> "vhptsize=24" so this can be changed at boot-time?
In fact, I have just reduced the VHPT size to see how Xen boots on more than 2 
procs.  It was a quick & dirty modification I forgot to remove.

> Anyone want to generate a patch for this?
I think this is a good idea.  I will add this on my todo list.

Tristan.


_______________________________________________
Xen-ia64-devel mailing list
Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ia64-devel