On 05/05/2017 12:02 AM, Huang, Ying wrote: >> The hybrid polling could help. The default hybrid polling poll half >> the average IO latency. But it will not work very well if the latency >> becomes very big. The hybrid polling has an interface to allow >> userspace to configure the poll threshold, but since the latency >> varies from time to time, it would be very hard to set a single >> threshold for all workloads. > > If my understanding were correct, the hybrid polling will insert some > sleep before the polling, but will not restrict the duration of the > polling itself. This helps CPU usage, but may not help much for very > long latency. How about add another threshold to restrict the max > polling time? For example, the sleep time + max polling time could be > 1.5 * mean latency. So that most IO requests could be serviced by > polling, and for very long latency, polling could be restricted to > reduce CPU usage. I don't think that's a bad idea at all, there's definitely room for improvement on how long to sleep and when to completely stop. The stats track min/avg/max for a given window of time, so it would not be too hard to implement an appropriate backoff as well. -- Jens Axboe -- 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>
