Re: [PATCH] memory: transaction API

Avi Kivity
2011-07-21T12:07:40Z

On 07/21/2011 02:04 PM, Ferry Huberts wrote:
> On 07/21/2011 12:21 PM, 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.
> >
> >
> > +void memory_region_transaction_begin(void)
> > +{
> > + ++memory_region_transaction_depth;
> > +}
> > +
>
> wouldn't you rather keep it safe by doing either here
>
> if (!memory_region_transaction_depth)
> memory_region_transaction_depth++;
>

Why? I want to allow nesting transactions (not that I anticipate such a
case).

> > +void memory_region_transaction_commit(void)
> > +{
> > + if (!memory_region_transaction_depth) {
> > + abort();
> > + }
>
>
> > + --memory_region_transaction_depth;
> > + memory_region_update_topology();
> > +}
> > +
>
> or by doing here
>
> while (!memory_region_transaction_depth)
> memory_region_transaction_depth--;
>
>
> with your setup nesting transactions will not work correctly I think.
> You seem to have designed it to not do nesting, so it's safer to make
> that explicit in your code imho

Nesting should work just fine.

> therefore I'd go for the change in _begin
>
> also, wouldn't you rather rename memory_region_transaction_depth to
> memory_region_transaction_pending?

The existing name works for me, but if people want it changed, that's
fine too.

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