[Xen-devel] RE: [PATCH][1/4] Enable 1GB for Xen HVM host page

["Huang2, Wei" <Wei.Huang2@xxxxxxx>]

The performance gain depends on applications. We have seen 5% performance 
improvement for certain benchmarks. But some have no perf. gains over 2MB (no 
performance degradation either). That is why I add an option to turn it off in 
case people don't want 1GB.

I didn't have access to my guest QEMU until applying this patch from Dongxiao. 
Dongxiao might have other comments.

-Wei

-----Original Message-----
From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx] 
Sent: Tuesday, February 23, 2010 1:57 AM
To: Huang2, Wei; 'xen-devel@xxxxxxxxxxxxxxxxxxx'; Xu, Dongxiao
Subject: Re: [PATCH][1/4] Enable 1GB for Xen HVM host page 

What's the performance gain from 1GB mappings in HAP tables like? What about
just the (possible) extra 1GB mapping from this particular patch? Is it
worth making guest-visible efforts like this (admittedly small) one? After
all, the probably most frequently accessed 1GB starting at address 0x0
cannot be done with a 1GB mapping and we live with it.

 -- Keir

On 22/02/2010 17:17, "Wei Huang" <wei.huang2@xxxxxxx> wrote:

> To support 1GB host page, this patch changes the MMIO starting address
> to 1GB boundary.
> 
> Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> Signed-off-by: Wei Huang <wei.huang2@xxxxxxx>
> 





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