Re: [Xen-devel] [PATCH 1 of 4 RFC] xen, p2m: get_entry returns level of entry as well

[Tim Deegan <tim@xxxxxxx>]

At 17:39 +0100 on 14 Jun (1339695541), George Dunlap wrote:
> On Thu, Jun 14, 2012 at 4:01 PM, George Dunlap
> <george.dunlap@xxxxxxxxxxxxx> wrote:
> > On 14/06/12 11:21, Tim Deegan wrote:
> >> This looks broadly correct, but it's a bit invasive.  If there's any way
> >> to rework patch 2 not to need it that would be helpful.  It looks like
> >> the main use is for detecting and removing superpage PoD entries; maybe
> >> that could be done with a sweep like you have in the non-PoD case?
> >
> > You mean the non-balloon case?  I forget why I thought that was a bad idea,
> > exactly.  Let me think about that.
> 
> I think I basically didn't want to have to do the full check of each
> of the 512 individual entries of the p2m in the case that it wasn't,
> in fact, a superpage; but I think in the common case it should either
> be a full superpage, or the check at the beginning of
> p2m_pod_zero_check_superpage() should fail out relatively early.  So
> we could probably get away without it.
> 
> Why don't I re-write patch 2 of this series to not require patch 1,
> and include it in my other series.  If there's a performance gain to
> be had by avoiding the check, we can discuss that post-4.2.

That sounds ideal.  Thanks,

Tim.

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