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

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Mon, Mar 26, 2007 at 12:19:47PM +1000, Herbert Xu wrote:
> This is actually one of the reasons I picked the grant tables interface
> originally in that we could unmap it at the same time rather than doing
> a full swap followed by an unmap.
> 
> So are you OK with adding underlying operations that allows a full swap
> of two p2m entries? This would then be used as follows in translated mode:
> 
>       a) new_addr = alloc_page
>       b) memcpy(new_addr, addr, len)
>       c) p2m_swap(__pa(new_addr), __pa(addr))
>       d) grant_unmap(__pa(new_addr))

Swaping the p2m entry on ia64 is easy.
However the following tlb flush cost for the newly allocated page
is extremly high on ia64.
Can alloc_page() at step a) be avoided?
For example batched page allocation and reusing allocated pfns by setting
PG_foreign. And I want arch hook before use/release those pages to
reduce tlb flush cost.
-- 
yamahata

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