RE: [Xen-ia64-devel] Shortage of Xen heap problem

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

I am mistaken... it's been a long time since I looked at this code.
The VHPT has its own DTR.  So expanding the Xen heap size should
work.  However the Xen 4GB memory limit (which may make as little
as 1GB of populated memory visible) may make increasing the Xen heap
size difficult until this limit is fixed.

For now, you may just want to configure a smaller VHPT size (which is
I think what Tristan did when he ran 48 processors).  Except for
when doing performance analysis or running large applications,
a smaller VHPT may not make a noticable difference.

Dan

> -----Original Message-----
> From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf 
> Of Masaki Kanno
> Sent: Thursday, December 22, 2005 2:21 AM
> To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-ia64-devel] Shortage of Xen heap problem
> 
> Hi,
> 
> Sorry, I forgot that. To map extended heap pages, assuming 64MB page, 
> I need 1 TR entry/4CPU. Is it OK to consume that much of TR 
> entries? or
> Should I use 256MB page ?
> 
> Best Regards,
>  Kan
> 
> Magenheimer, Dan (HP Labs Fort Collins) wrote:
> >Is it assumed that the entire Xen heap is mapped by
> >a TR?   If so, expanding the Xen heap size might
> >cause problems. 
> >
> >> -----Original Message-----
> >> From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> >> [mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf 
> >> Of Masaki Kanno
> >> Sent: Tuesday, December 20, 2005 1:11 AM
> >> To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >> Subject: [Xen-ia64-devel] Shortage of Xen heap problem
> >> 
> >> Hi,
> >> 
> >> When Xen SMP is supported, it becomes Xen heap shortage with 
> >> 3 CPUs or more.
> >> Because Xen heap is required 16MB per CPU for VHPT. 
> >> (Refer to attached file Xenheapshortage.txt)
> >> 
> >> I think that I will expand the size of Xen heap according to 
> >> the value of NR_CPUS. 
> >> I have the idea as follows.
> >> 
> >> #ifdef CONFIG_SMP
> >>   Xen heap size = 63MB(default) + 16MB * NR_CPUS;
> >> #else
> >>   Xen heap size = 63MB(default);
> >> #endif
> >> 
> >> Any idea and comment?
> >> 
> >> Best Regards,
> >>  Kan
> >> 
> >> 
> 
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