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Re: [Xen-devel] New heap API and scrubbing

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>
Subject: Re: [Xen-devel] New heap API and scrubbing
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Tue, 10 Feb 2009 08:22:27 +0000
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>>> Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> 10.02.09 01:24 >>>
>So in the new (soon-to-be 3.4) heap API, are
>
>alloc_domheap_pages(NULL,order,flags)
>
>and
>
>alloc_xenheap_pages(order,flags)
>
>synonomous on 64-bit hypervisors?  I.e. they
>are allocating from the same pool of pages?

I thought thee was a small difference, but in looking at the code it seems
there isn't at present. The difference I though would be there was that
alloc_xenheap_pages() should be allowed to access MEMZONE_XEN,
while alloc_domheap_pages() should only start allocating at MEMZONE_XEN+1.
That way, by default Xen heap allocations would eat from the domain heap,
but if that's empty would be allowed to fall back to the low memory portion.
Keir?

>And if so are the matching free routines
>synonomous?

No, because PGC_xen_heap must be cleared on pages allocated through
alloc_xenheap_pages().

Jan


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