On 06/22/2015 05:26 PM, Paul E. McKenney wrote: > OK, here is an experimental patch that provides a fast-readers variant > of RCU, forward-ported from v3.3. Because we didn't have call_srcu() > and srcu_barrier() back then, it is not a drop-in replacement for SRCU, > so you need to adapt the code to the API, which means putting an "fr" > in front of the "srcu" in the API members. > > Understood on the overhead of the memory-barrier instruction showing > up consistently. My point was instead that getting rid of this > memory-barrier instruction does not come for free, as it greatly > increases the latency of synchronize_frsrcu(). In a real workload, > it is entirely possible that the savings from eliminating the memory > barrier are overwhelmed by the increased grace-period latency. > > Anyway, the patch is below. Very lightly tested.
This does give a very similar performance boost as the other optimization I posted. I measured this patch to boost the writes/second by 11.0% while my previous optimization did 10.8%. I don't think this workload will see any of the overhead of the synchronize_frsrcu(), though, but this helps confirm the source of the overhead. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
