Tejun Heo wrote on 2021/7/27 5:46: > Hello, > > On Tue, Jul 20, 2021 at 12:35:54AM +0800, brookxu wrote: >> In order to avoid code duplication and IOPS stability problems caused by estimating >> the equivalent number of IOs, and to avoid potential deadlock problems caused by >> synchronization through queue_lock. I tried to count the number of splited IOs in >> the current window through two atomic counters. Add the value of the atomic variable >> when calculating io_disp[rw], which can also avoid the problem of inaccurate IOPS in >> large IO scenarios. How do you think of this approach? Thanks for your time. > > I guess it's okay but am still not a big fan of adding another hook. This is > primarily because blk-throtl is sitting too early in the stack - e.g. rq_qos > is doing the same thing but sits after the split path - and it's a bit nasty > to add an additional hook for it. > > Do you think it can be an option to relocate the blk-throtl hooks to the > same spots as rq-qos or, even better, make it use rq-qos? Make blk-throttle use rq-qos may be more elegant. But I found that there may be at least one problem that is difficult to solve. blk-throttle supports separate throttle for read and write IOs, which means that we cannot suspend tasks during throttle, but rq-qos throttle IOs by suspending tasks. We may be able to relocate the blk-throttle hooks to the rq-qos hooks. Since we may not be able to replace the throttle hook, in this case, if we register a rq-qos to the system, part of the blk-throttle hooks is in rq-qos and part hooks not, which feels a bit confusing. In addition, we may need to implement more hooks, such as IO merge hook. Thanks for you time. > Thanks. >
