Re: [patch 04/41] cpu ops: Core piece for generic atomic per cpu operations

Rusty Russell
2008-06-12T02:44:33Z

On Thursday 12 June 2008 10:58:01 Nick Piggin wrote:
> On Thursday 12 June 2008 09:39, Christoph Lameter wrote:
> > On Wed, 11 Jun 2008, Rusty Russell wrote:
> > > > 4. The modeling of local_t on atomic_t limits it to 32bit!
> > >
> > > Again wrong. And adding an exclamation mark doesn't make it true.
> >
> > Ewww ... Its atomic_long_t ahh. Ok then there no 32 bit support. What
> > about pointers?
>
> sizeof(long) == sizeof(void *) in Linux, right?
>
> If you were to support just a single data type, long would probably
> be the most useful. Still, it might be more consistent to support
> int and long, same as atomic.

Sure, but in practice these tend to be simple counters: that could well change
when dynamic percpu allocs become first class citizens, but let's not put the
cart before the horse...

Per-cpu seems to be particularly prone to over-engineering: see commit
7ff6f08295d90ab20d25200ef485ebb45b1b8d71 from almost two years ago. Grepping
here reveals that this infrastructure is still not used.

Cheers,
Rusty.