Hi Paolo, On 18/4/27 01:27, Paolo Valente wrote: > > >> Il giorno 25 apr 2018, alle ore 14:13, Joseph Qi <jiangqi903@xxxxxxxxx> ha scritto: >> >> Hi Paolo, >> > > Hi Joseph > >> ... >> Could you run blktrace as well when testing your case? There are several >> throtl traces to help analyze whether it is caused by frequently >> upgrade/downgrade. > > Certainly. You can find a trace attached. Unfortunately, I'm not > familiar with the internals of blk-throttle and low limit, so, if you > want me to analyze the trace, give me some hints on what I have to > look for. Otherwise, I'll be happy to learn from your analysis. > I've taken a glance at your blktrace attached. It is only upgrade at first and then downgrade (just adjust limit, not to LIMIT_LOW) frequently. But I don't know why it always thinks throttle group is not idle. For example: fio-2336 [004] d... 428.458249: 8,16 m N throtl avg_idle=90, idle_threshold=1000, bad_bio=10, total_bio=84, is_idle=0, scale=9 fio-2336 [004] d... 428.458251: 8,16 m N throtl downgrade, scale 4 In throtl_tg_is_idle(): is_idle = ... || (tg->latency_target && tg->bio_cnt && tg->bad_bio_cnt * 5 < tg->bio_cnt); It should be idle and allow run more bandwidth. But here the result shows not idle (is_idle=0). I have to do more investigation to figure it out why. You can also filter these logs using: grep throtl trace | grep -E 'upgrade|downgrade|is_idle' Thanks, Joseph
