Re: [Xen-devel] non-contiguous allocations

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 06.05.11 at 12:25, Olaf Hering <olaf@xxxxxxxxx> wrote:
> On Tue, Apr 26, Jan Beulich wrote:
> 
>> >>> On 18.04.11 at 20:45, Olaf Hering <olaf@xxxxxxxxx> 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.
>> > 
>> > how do I allocate a few mfns and give them a virtual address?
>> > I dont find a malloc like interface to allocate random pages.
> 
>> Otherwise I think the only option is to introduce indirection (using
>> the 1:1 mapping, and setting up an array of pointers). That may
>> however be a little difficult if (and I think that's the case) data
>> chunks aren't always of the same size (as then you need to deal
>> with the roll-over into the next page).
> 
> I'm almost done with the per-page handling in __insert_record().
> I just need to figure out the a usable address of a given mfn.
> Is the u8 *p = mfn_to_virt(mfn) the same as page_to_virt(mfn_to_page(mfn))?

Yes.

Jan

> 
> Olaf




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