Re: [RFC PATCH 1/6] kernel: implement queue spinlock API

[John Stultz]

On 02/07/2013 02:34 PM, Paul E. McKenney wrote:
> On Tue, Jan 22, 2013 at 03:13:30PM -0800, Michel Lespinasse wrote:
> > Introduce queue spinlocks, to be used in situations where it is desired
> > to have good throughput even under the occasional high-contention situation.
> >
> > This initial implementation is based on the classic MCS spinlock,
> > because I think this represents the nicest API we can hope for in a
> > fast queue spinlock algorithm. The MCS spinlock has known limitations
> > in that it performs very well under high contention, but is not as
> > good as the ticket spinlock under low contention. I will address these
> > limitations in a later patch, which will propose an alternative,
> > higher performance implementation using (mostly) the same API.
> >
> > Sample use case acquiring mystruct->lock:
> >
> >    struct q_spinlock_node node;
> >
> >    q_spin_lock(&mystruct->lock, &node);
> >    ...
> >    q_spin_unlock(&mystruct->lock, &node);
> It is possible to keep the normal API for MCS locks by having the lock
> holder remember the parameter in the lock word itself.  While spinning,
> the node is on the stack, is not needed once the lock is acquired.
> The pointer to the next node in the queue -is- needed, but this can be
> stored in the lock word.
>
> I believe that John Stultz worked on something like this some years back,
> so added him to CC.
Oh yea, its been quite awhile.

Here are some of the discussion threads google remembers for me:

http://marc.info/?l=lse-tech&m=101227079817027&w=2

http://marc.info/?l=lse-tech&m=101380783015065&w=2  (missing the patch)
    http://marc.info/?l=lse-tech&m=101380783615084&w=2 (patch for above)


thanks
-john


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