[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Proposed new "memory capacity claim" hypercall/feature



> From: Tim Deegan [mailto:tim@xxxxxxx]
> Subject: Re: Proposed new "memory capacity claim" hypercall/feature

Oops, missed an important part of your response... I'm glad
I went back and reread it...
 
> The claim hypercall _might_ fix (c) (if it could handle allocations that
> need address-width limits or contiguous pages).

I'm still looking into this part.

It's my understanding (from Jan) that, post-dom0-launch, there are
no known memory allocation paths that _require_ order>0 allocations.
All of them attempt a larger allocation and gracefully fallback
to (eventually) order==0 allocations.  I've hacked some code
in to the allocator to confirm this, though I'm not sure how
to test the hypothesis exhaustively.

For address-width limits, I suspect we are talking mostly or
entirely about DMA in 32-bit PV domains?  And/or PCI-passthrough?
I'll look into it further, but if those are the principal cases,
I'd have no problem documenting that the claim hypercall doesn't
handle them and attempts to build such a domain might still
fail slowly.  At least unless/until someone decided to add
any necessary special corner cases to the claim hypercall.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.