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xen-ia64-devel
Re: [Xen-devel] [PATCH 1/5 TAKE 2] xenoprof: split xen x86 xenoprof code
On Fri, Nov 17, 2006 at 01:26:04PM -0600, Santos, Jose Renato G wrote:
> > > QUESTIONS for Isaku:
> > >
> > > patch 4/5:
> > > ==========
> > >
> > > > +struct xenoprof_shared_buffer {
> > > > + char *buffer;
> > > > + struct xenoprof_arch_shared_buffer arch;
> > > > +};
> > >
> > > The arch field has no extra info for x86. Why do you need this?
> >
> > On IA64 it is defined as
> > struct xenoprof_arch_shared_buffer {
> > struct resource* res;
> > };
> >
> > On IA64, auto translated mode feature is enabled.
> > It means that page mapping from xen is based on pseudo
> > physical address, not virtual address. Pseudo physical
> > address used to map pages must be recorded somewhere in order
> > to unmap.
> > I guess, if xenoprof/x86 supported auto translated guest mode
> > something similar structure would be necessary.
> >
> >
> Isaku
>
> I am still not convinced that we need this. Since this in the kernel
> you can always get the pseudo physical address from the virtual address,
> right? Am I missing something?
Yes, the pseudo physical address itself can be get.
The point is that the pseudo physical addresses aren't always
backed by struct page.
In such a case alloc_pages()/free_pages() can't be used, another structure
is necessary.
In fact Xen/IA64 allocates the pseudo physical address resion by
allocate_resource(&iomem_resource, ...). Not by alloc_pages().
Why doesn't Xen/IA64 use alloc_pages()?
Because it is also used for grant table foreign domain page mapping
and its size is very large sometimes. Using alloc_pages() results in OOM.
Xen/PPC seems to adopt another approach, though.
> I applied your patches to changeset 12446 but they are failing to
> compile. I have attached the make output below
>
> Could you please fix this and resend?
Sorry for that.
It should compile with CONFIG_PROFILING=y and CONFIG_OPORIFLE=y.
Anyway I'll fix and resend.
--
yamahata
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