Hello, Yu Kuai. On Mon, Apr 22, 2024 at 11:47:41AM +0800, Yu Kuai wrote: > Hi! > > 在 2024/04/22 11:33, 周泰宇 写道: > > What I want to do here was to set an easy to reach value to BPS_LIMIT (10M/s in this example) and an unable to reach value to IOPS_LIMIT (100000 in this example). > > > > > > Under this setting, the iostat shows that the bps is far less than 10M/s and sometimes is far larger than 10M/s. > > Yes, I know this behaviour, and this is because blk-throttle works > before IO split, and io stats is accounting bps for rq-based disk after > IO split, if you using Q2C for bps you'll see that bps is stable as > limit. > > Hi, Tejun！ > > Do you think this *phenomenon* need to be fixed? If so, I don't see a > easy way other than throttle bio after *IO split*. Perhaps ohter than > bio merge case, this can be another motivation to move blk-throttle to > rq_qos_throttle(). Yeah, blk-throtl is sitting too early in the pipeline to easily track how the bios actually get issued. However, given that it's been available for bio-based drivers for a really long time, I don't think it'd be a good idea to move it, so iops limit is always going to be a bit unreliable w.r.t. what actually get issued to the device. So, IMHO, if the oddity is just about how IOs are counted, I don't think it's a critical problem on its own. Thanks. -- tejun
