On 2021-12-17 09:25:25 [-0800], Song Liu wrote: > > The delay is a jiffy so it depends on CONFIG_HZ. You do benchmark for > > the best algorithm and if you get preempted during that period then your > > results may be wrong and you make a bad selection. > > With current code, the delay _should be_ 16 jiffies. However, the experiment > hits way longer latencies. I agree this may cause inaccurate benchmark results > and thus suboptimal RAID algorithm. Everything less than CONFIG_PREEMPT does not have an explicit requirement for preemption so higher latencies are not unusual. *If* this is a problem on <= PREEMPT_VOLUNTARY then a cond_resched() between loops would be the usual thing to do. But only *if* it is a real problem which I doubt. It is not a preemtible kernel after all… > I guess the key question is whether long latency at module loading time matters. > If that doesn't matter, we should just drop this. Correct. And should this be problematic on PREEMPT_RT then I would restrict CONFIG_RAID6_PQ_BENCHMARK to !PREEMPT_RT. > Thanks, > Song Sebastian
