Re: [Xen-devel] RFC: [0/2] Remove netloop by lazy copying in netback

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 27/3/07 11:15, "Herbert Xu" <herbert@xxxxxxxxxxxxxxxxxxx> wrote:

>> Could we shatter the ia64 guest large mappings easily? They have no benefit
>> on Xen anyway apart from some inconsequential memory saving.
> 
> I think large pages are needed in general not to reduce memory usage,
> but to reduce TLB usage.  I'm not sure about ia64, but for other
> architectures it's quite important.
> 
> So getting rid of them will add a non-trivial cost.

Is this a virtual TLB we're talking about? Xen will already have to
implicitly shatter the large mappings before updating the real TLB, since
guest machine memory map is not contiguous at the scale of large pages (even
if we tried at domain build time, it certainly wouldn't be the case when
foreign grant mappings are scattered all over the place).

 -- Keir


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