* Ingo Molnar <mingo@xxxxxxx> [2009-03-04 18:33:21]: > > * Arun R Bharadwaj <arun@xxxxxxxxxxxxxxxxxx> wrote: > > > $taskset -c 4,5,6,7 make -j4 > > > > my_driver queuing timers continuously on CPU 10. > > > > idle load balancer currently on CPU 15 > > > > > > Case1: Without timer migration Case2: With timer migration > > > > -------------------- -------------------- > > | Core | LOC Count | | Core | LOC Count | > > | 4 | 2504 | | 4 | 2503 | > > | 5 | 2502 | | 5 | 2503 | > > | 6 | 2502 | | 6 | 2502 | > > | 7 | 2498 | | 7 | 2500 | > > | 10 | 2501 | | 10 | 35 | > > | 15 | 2501 | | 15 | 2501 | > > -------------------- -------------------- > > > > --------------------- -------------------- > > | Core | Sleep time | | Core | Sleep time | > > | 4 | 0.47168 | | 4 | 0.49601 | > > | 5 | 0.44301 | | 5 | 0.37153 | > > | 6 | 0.38979 | | 6 | 0.51286 | > > | 7 | 0.42829 | | 7 | 0.49635 | > > | 10 | 9.86652 | | 10 | 10.04216 | > > | 15 | 0.43048 | | 15 | 0.49056 | > > --------------------- --------------------- > > > > Here, all the timers queued by the driver on CPU10 are moved to CPU15, > > which is the idle load balancer. > > The numbers with this automatic method based on the ilb-cpu look > pretty convincing. Is this what you expected it to be? Yes Ingo, this is the expected results and looks pretty good. However there are two parameters controlled in this experiment: 1) The system is moderately loaded with kernbench so that there are some busy CPUs and some idle cpus, and the no_hz mask is does not change often. This leads to stable ilb-cpu selection. If the system is either completely idle or loaded too little leading to ilb nominations, then timers keep following the ilb cpu and it is very difficult to experimentally observe the benefits. Even if the ilb bounces, consolidating timers should increase overlap between timers and reduce the wakeup from idle. Optimising the ilb selection should significantly improve experimental results for this patch. 2) The timer test driver creates quite large timer load so that the effect of migration is observable as sleep time difference on the expected target cpu. This kind of timer load may not be uncommon with lots of application stack loaded in an enterprise system --Vaidy _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
