On 6/15/13 10:47 AM, "Jim Dinan" <[email protected]<mailto:[email protected]>> wrote: Can you elaborate on the source of performance loss from operations between Iflush and its completion? With the current semantics of flush, a valid implementation is a counter of number of operations started, another of operations completed, wait until they're equal. On an unordered channel (and acks are usually on an unordered channel), this mode won't work and you either have to have multiple counters or start tracking events in some per-event way, neither of which are going to be as performant. Brian -- Brian W. Barrett Scalable System Software Group Sandia National Laboratories