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Re: [Xen-devel] Re: non-contiguous allocations

  • To: Olaf Hering <olaf@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <keir.xen@xxxxxxxxx>
  • Date: Fri, 06 May 2011 19:46:54 +0100
  • Cc:
  • Delivery-date: Fri, 06 May 2011 11:47:50 -0700
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
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  • Thread-topic: [Xen-devel] Re: non-contiguous allocations

On 06/05/2011 19:12, "Olaf Hering" <olaf@xxxxxxxxx> wrote:

> On Mon, Apr 18, Olaf Hering wrote:
>> On Fri, Apr 01, George Dunlap wrote:
>>> On Wed, 2011-03-30 at 19:04 +0100, Olaf Hering wrote:
>>>> Using the u16 means each cpu could in theory use up to 256MB as trace
>>>> buffer. However such a large allocation will currently fail on x86 due
>>>> to the MAX_ORDER limit.
>>> FWIW, I don't believe that there's any reason the allocations have to be
>>> contiguous any more.  I kept them contiguous to minimize the changes to
>>> the moving parts near a release.  But the new system has been pretty
>>> well tested now, so I think looking at non-contiguous allocations may be
>>> worthwhile.
> Is there a way to allocate more than 128mb with repeated calls to
> alloc_xenheap_page()?

Yes it should just work. Are you sure you actually have more than 128MB
available (not all allocated to dom0 for example)?

>  From which pool should the per-cpu tracebuffers
> get allocated?  alloc_domheap_page() wants a domain, so I think thats
> the wrong interface.

Yes, sticking with alloc_xenheap_pages() is good.

 -- Keir

> Olaf
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