Fw: bigphysarea patch on xen capable linux

Fw: bigphysarea patch on xen capable linux

[Kashmira. K.]

Forwarding to xen-devel

--- On Tue, 1/5/10, Kashmira. K. <chimnee@yahoo.com> wrote:

> From: Kashmira. K. <chimnee@yahoo.com>
> Subject: bigphysarea patch on xen capable linux
> To: xen-users@lists.xensource.com
> Date: Tuesday, January 5, 2010, 1:31 PM
> Hello Xen Experts
> 
> I am trying to port a linux application or rather a user
> mode linux driver (not built into the kernel) to Xen capable
> linux. This will be running in Dom0. This user mode driver
> used the linux pigphysarea patch to allocate large (over
> 1Gig) physically contiguous memory.
> 
> I have two questions:
> 
> 1. Is the bigphysarea patch supported on Xen capable
> linux?  If not what is the maximum physically
> contiguous memory Xen provides.
> 
> 2. If I were to run my application in DomU instead of Dom0,
> can the bigphysarea patch  be used then.
> 
> Thanks in advance.
> Kashmira
> 
> 
> 
>       
> 

Re: Fw: bigphysarea patch on xen capable linux

[Jan Beulich]

>>> "Kashmira. K." <chimnee@yahoo.com> 08.01.10 02:10 >>>
> 1. Is the bigphysarea patch supported on Xen capable
> linux?  If not what is the maximum physically
> contiguous memory Xen provides.

2Mb is the maximum you can create.
 
> 2. If I were to run my application in DomU instead of Dom0,
> can the bigphysarea patch  be used then.

In a fully virtualized DomU this should be possible (unless you imply to
be able to use 1G pages).

Jan

Re: Fw: bigphysarea patch on xen capable linux

[Kashmira. K.]

Hi Jan,

I looked at the linux code xen_create_contiguous_region(). It appears the 2MB limit comes from the #define MAX_CONIG_ORGER 9. Could that be modified to get more than 2MB. 

If not would you have other suggestions of how I can I get around 500M or more of physically contiguous memory on Xen in Dom0 linux. 

Thanks
Kashmira

--- On Tue, 1/12/10, Jan Beulich <JBeulich@novell.com> wrote:

> From: Jan Beulich <JBeulich@novell.com>
> Subject: Re: [Xen-devel] Fw: bigphysarea patch on xen capable linux
> To: "Kashmira. K." <chimnee@yahoo.com>
> Cc: xen-devel@lists.xensource.com
> Date: Tuesday, January 12, 2010, 12:53 AM
> >>> "Kashmira. K." <chimnee@yahoo.com>
> 08.01.10 02:10 >>>
> > 1. Is the bigphysarea patch supported on Xen capable
> > linux?  If not what is the maximum physically
> > contiguous memory Xen provides.
> 
> 2Mb is the maximum you can create.
>  
> > 2. If I were to run my application in DomU instead of
> Dom0,
> > can the bigphysarea patch  be used then.
> 
> In a fully virtualized DomU this should be possible (unless
> you imply to
> be able to use 1G pages).
> 
> Jan
> 
> 

Re: Fw: bigphysarea patch on xen capable linux

[Keir Fraser]

You can increase MAX_CONTIG_ORDER and then it could work. The cost is a
larger kernel image size for the enlarged static arrays defined immediately
above xen_create_contiguous_region().

 -- Keir

On 12/01/2010 20:49, "Kashmira. K." <chimnee@yahoo.com> wrote:

> 
> Hi Jan,
> 
> I looked at the linux code xen_create_contiguous_region(). It appears the 2MB
> limit comes from the #define MAX_CONIG_ORGER 9. Could that be modified to get
> more than 2MB. 
> 
> If not would you have other suggestions of how I can I get around 500M or more
> of physically contiguous memory on Xen in Dom0 linux.
> 
> Thanks
> Kashmira
> 
> --- On Tue, 1/12/10, Jan Beulich <JBeulich@novell.com> wrote:
> 
>> From: Jan Beulich <JBeulich@novell.com>
>> Subject: Re: [Xen-devel] Fw: bigphysarea patch on xen capable linux
>> To: "Kashmira. K." <chimnee@yahoo.com>
>> Cc: xen-devel@lists.xensource.com
>> Date: Tuesday, January 12, 2010, 12:53 AM
>>>>> "Kashmira. K." <chimnee@yahoo.com>
>> 08.01.10 02:10 >>>
>>> 1. Is the bigphysarea patch supported on Xen capable
>>> linux?  If not what is the maximum physically
>>> contiguous memory Xen provides.
>> 
>> 2Mb is the maximum you can create.
>>  
>>> 2. If I were to run my application in DomU instead of
>> Dom0,
>>> can the bigphysarea patch  be used then.
>> 
>> In a fully virtualized DomU this should be possible (unless
>> you imply to
>> be able to use 1G pages).
>> 
>> Jan
>> 
>> 
> 
> 
>       
> 
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