Re: [Qemu-devel] [PATCH 14/23] memory: transaction API

[Avi Kivity]

On 07/25/2011 10:16 PM, Anthony Liguori wrote:
> On 07/25/2011 09:02 AM, Avi Kivity wrote:
> > Allow changes to the memory hierarchy to be accumulated and
> > made visible all at once.  This reduces computational effort,
> > especially when an accelerator (e.g. kvm) is involved.
> >
> > Useful when a single register update causes multiple changes
> > to an address space.
> >
> > Signed-off-by: Avi Kivity<address@hidden>
>
> What's the motivation for this?  Was this just because it seemed neat 
> to do or did you run into a performance issue you were trying to solve?

Both cirrus and 440fx need this; look at i440fx_update_memory_mappings() 
for example, it blindly updates mappings even for PAMs which haven't 
changed.

These issues can be also solved by more care on the caller's side, or by 
making the API richer, but it's good to have a no-thought-required 
solution, particularly as it's so easy to do.

--
error compiling committee.c: too many arguments to function