Greetings, my first try with this patch did not draw any comment. So lets try again, this time with linux-arch on CC. I've been working on the cpu idle/wakeup path to improve the performance of some ping-pong workloads. This patch is the latest idea and proved rather effective. The idea is that the timer tick is not switched off if the cpu did some work in the last tick period. This will add an unnecessary tick interrupt if the cpu goes truly idle but will save some cycles for the nohz reprogramming if the cpu wakes up again for more work. For ping-pong like workload this is an overall win. Currently only s390 has a non-zero arch_needs_cpu. It will be true if there has been any other interrupt than timer interrupts in the last tick period. I think this could be improved with an explicit call to request a nohz delay. The call should be added to selective points in the code, e.g. whenever a process != idle is scheduled, whenever a bottom half is run, and so on. It works well enough on s390 as it is though. Does anyone have a problem with the patch? Otherwise I would like to push it upstream as it gives us a nice improvement for s390. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
