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Re: [Xen-devel] non-contiguous allocations

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] non-contiguous allocations
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Fri, 6 May 2011 12:25:57 +0200
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>
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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))?


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