Re: [PATCH][RFC]Provide fast write emulation path to release shadow lock

[Tim Deegan <Tim.Deegan@citrix.com>]

At 10:20 +0800 on 22 Jan (1200997253), Tian, Kevin wrote:
> We also did series of tests on 32/32pae/32e: (host is 32e)
>                    32       32pae       32e
> ----Linux----
> kernel build   +1%    +0.86%    +1.9%
> Specjbb        +0.9% +1.61%    +0.32%
> 
> ----XP----
> Sysbench     N/A     -0.05%     -0.32%(*)
> 
> * Sysbench score is not very stable on 32e guest, with up
> to 6% variation observed in 5 rounds running. 32pae is
> stable. 32 XP image was unfortunately corrupted at test 
> cycle, so not test yet. Don't want to hold here from getting
> early comments. :-)
> 
> I thought the performance gain should be straightforward
> with this patch, and thus would like to know comment
> like:
> 	- Is it a right direction?

Looks good to me! 

> 	- Is there anything wrong or missed in patch?

Nothing fundamental that I can see by reading through it.  One thing I'd
change is to avoid introducing "vfn": a virtual address >> PAGE_SIZE is
just a "page number".

> 	- Any more benchmarks should we test?

Anything and everything. :)  Specially multi-vcpu mixed operations
(e.g. kernel compile + ltp + network traffic) while doing live migrate.
Even when they look as clean as this one, changes in the shadow fault
handler tend to chase out implicit/forgotten assumptions.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@citrix.com>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]