Re: [Xen-devel] [PATCH v2 0/4] xen: enable EPT A/D bit feature

["Hao, Xudong" <xudong.hao@xxxxxxxxx>]

> -----Original Message-----
> From: Tim Deegan [mailto:tim@xxxxxxx]
> Sent: Monday, June 25, 2012 5:02 PM
> To: Hao, Xudong
> Cc: xen-devel@xxxxxxxxxxxxx; Shan, Haitao; keir@xxxxxxx; Zhang, Xiantao;
> JBeulich@xxxxxxxx
> Subject: Re: [Xen-devel] [PATCH v2 0/4] xen: enable EPT A/D bit feature
> 
> At 09:57 +0800 on 20 Jun (1340186263), Xudong Hao wrote:
> > Changes from v1:
> > - Move hap_has_dirty_bit and hap_has_access_bit definition from patch 3 to
> patch2.
> > - define them as bool_t instead of int.
> >
> > Extended Page Tables introduce two bit: access bit and dirty bit, A/D bits
> > enable VMMs to efficiently implement memory management and page
> classification
> > algorithms to optimize VM memory operations.
> >
> > This series of patches enable EPT dirty bit feature for guest live 
> > migration.
> 
> Thanks for this.  I have a few high-level questions:
> 
> - You're proposing this for after 4.2, right?
> 

Yes, they are not targeted to 4.2.

> - Have you measured what difference this makes?  I take it it improves
>   performance during live migration but it would be good to know how much
>   before taking on extra code.
> 

We did live migration performance testing with patches, it's embarrassed to say 
but the result show there is no performance gain and no performance loss indeed.

> - Is this intended to replace the old log-dirty mechanism for vram
>   tracking as well?  It looks like it does that, but the description
>   doesn't mention it.
> 

Yes, it changes log-dirty mechanism for vram tracking when EPT dirty bit 
support, but it does not replace old log-dirty if no EPT dirty bit feature.
I'll add description after you further review.

> I'll be reviewing te patches in more detail later in the week.
> 

Thanks.


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