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Re: [Xen-devel] page ref/type count overflows


  • To: Jan Beulich <jbeulich@xxxxxxxxxx>
  • From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Date: Mon, 26 Jan 2009 17:01:42 +0000
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 26 Jan 2009 09:02:03 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acl/xfRBkJKnJktJZ0mYMPoY9oAMngAEc6T+
  • Thread-topic: [Xen-devel] page ref/type count overflows

On 26/01/2009 14:54, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

>> The count_info one only, or are you also intending to change _domain?
>> With struct page_info pretty large already, I'd want to avoid growing it
>> needlessly.
> 
> I'm going to change both and do it the easy way, growing the structure from
> 40 to 48 bytes. You can shrink it again with the tricks you describe if
> you're keen. I'm not sure how ugly the list stuff would end up, which would
> be my main concern, but I suppose you can hide it behind list.h-style
> macros. I don't see there's much duplication of effort to phase the work
> like this.

By the way, unless you can see some really clever way to shrink page_info to
32 bytes then I think it is only worth doing compression tricks on the
list_head field, to save 8 bytes (struct becomes 40 bytes). Compressing the
domain field won't get you down to another multiple-of-eight size. It may be
a trick to keep in mind for future though...

And all my stuff is in, as of changeset 19093.

 -- Keir



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