On 2/20/22 11:37 AM, Olivier Langlois wrote: > On Sat, 2022-02-19 at 17:22 -0700, Jens Axboe wrote: >> >> Outside of this, I was hoping to see some performance numbers in the >> main patch. Sounds like you have them, can you share? >> > Yes. > > It is not much. Only numbers from my application and it is far from > being the best benchmark because the result can be influenced by > multiple external factors. > > Beside addressing the race condition remaining inside io_cqring_wait() > around napi_list for v2 patch, creating a benchmark program that > isolate the performance of the new feature is on my todo list. > > I would think that creating a simple UDP ping-pong setup and measure > RTT with and without busy_polling should be a good enough test. Yes, a separate targeted test like that would be very useful and interesting indeed! > In the meantime, here are the results that I have: > > Without io_uring busy poll: > reaction time to an update: 17159usec > reaction time to an update: 19068usec > reaction time to an update: 23055usec > reaction time to an update: 16511usec > reaction time to an update: 17604usec > > With io_uring busy poll: > reaction time to an update: 15782usec > reaction time to an update: 15337usec > reaction time to an update: 15379usec > reaction time to an update: 15275usec > reaction time to an update: 15107usec OK, that's a pretty good improvement in both latency and deviation/consistency. Is this using SQPOLL, or is it using polling off cqring_wait from the task itself? Also something to consider for the test benchmark app, should be able to run both (which is usually just setting the SETUP_SQPOLL flag or not, if done right). > Concerning my latency issue with busy polling, I have found this that > might help me: > https://lwn.net/ml/netdev/20201002222514.1159492-1-weiwan@xxxxxxxxxx/ > -- Jens Axboe
