On Mon, Aug 29, 2022 at 04:36:40PM -0400, Joel Fernandes wrote: > On Mon, Aug 29, 2022 at 3:46 PM Frederic Weisbecker <frederic@xxxxxxxxxx> wrote: > > On Mon, Aug 29, 2022 at 12:45:40PM -0400, Joel Fernandes wrote: > > > On 8/29/2022 9:40 AM, Frederic Weisbecker wrote: [ . . . ] > > > > 2) NOCB implies performance issues. > > > > > > Which kinds of? There is slightly worse boot times, but I'm guessing that's do > > > with the extra scheduling overhead of the extra threads which is usually not a > > > problem except that RCU is used in the critical path of boot up (on ChromeOS). > > > > I never measured it myself but executing callbacks on another CPUs, with > > context switches and locking can only involve significant performance issues if callbacks > > are frequent. So it's a tradeoff between power and performance. > > In my testing of benchmarks on real systems with 8-16 CPUs, the > performance hit is down in the noise. It is possible though that maybe > one can write a non-realistic synthetic test to force the performance > issues, but I've not seen it in the real world. Maybe on > networking-heavy servers with lots of cores, you'll see it but their > batteries if any would be pretty big :-). To Frederic's point, if you have enough servers, even a 1% decrease in power consumption is a very big deal. ;-) Thanx, Paul
