Re: [PATCH] New operation for kref to help avoid locks

[Nick Piggin]

Corey Minyard wrote:
> Arjan van de Ven wrote:
>
> > > Just doing an atomic operation is not faster than doing a lock, an 
> > > atomic operation, then an unlock?  Am I missing something?
> > >   
> >
> >
> > if the lock and the atomic are on the same cacheline they're the same
> > cost on most modern cpus...
> >  
> Ah, I see.  Not likely to ever be the case with this.  The lock will 
> likely be with the main data structure (the list, or whatever) and the 
> refcount will be in the individual item in the main data structure (list 
> entry).

Is get_with_check actually going to be useful for anything? It
seems like it promotes complex and potentially unsafe schemes.

eg. In your queue example, it would usually be better to have
a refcount for being on queue, and entry_completed would remove
the entry from the queue and accordingly drop the refcount. The
release function would then just free it.

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