* Mel Gorman <mgorman@xxxxxxx> wrote: > > Whatever we did right in v3.4 we want to do in v3.13 as well - or > > at least understand it. > > Also agreed. I started a bisection before answering this mail. It > would be cooler and potentially faster to figure it out from direct > analysis but bisection is reliable and less guesswork. Trying to guess can potentially last a _lot_ longer than a generic, no-assumptions bisection ... The symptoms could point to anything: scheduler, locking details, some stupid little change in a wakeup sequence somewhere, etc. It might even be a non-deterministic effect of some timing change causing the workload 'just' to avoid a common point of preemption and not scheduling as much - and become more unfair and thus certain threads lasting longer to finish. Does the benchmark execute a fixed amount of transactions per thread? That might artificially increase the numeric regression: with more threads it 'magnifies' any unfairness effects because slower threads will become slower, faster threads will become faster, as the thread count increases. [ That in itself is somewhat artificial, because real workloads tend to balance between threads dynamically and don't insist on keeping the fastest threads idle near the end of a run. It does not invalidate the complaint about the unfairness itself, obviously. ] Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>