On Wed, Aug 16, 2023 at 09:27:06AM +0800, Yu Kuai wrote: > From: Yu Kuai <yukuai3@xxxxxxxxxx> > > carryover_ios/bytes[] can be negative in the case that ios are > dispatched in the slice in advance, and then configuration is updated. > For example: > > 1) set iops limit to 1000, and slice start is 0, slice end is 100ms; > 2) current time is 0, and 100 ios are dispatched, those ios will not be > throttled, hence io_disp is 100; > 3) still at current time 0, update iops limit to 100, then carryover_ios > is (0 - 100) = -100; > 4) then, dispatch a new io at time 0, the expected result is that this > io will wait for 1s. The calculation in tg_within_iops_limit: > > io_disp = 0; > io_allowed = calculate_io_allowed + carryover_ios > = 10 + (-100) = -90; > io won't be throttled if (io_disp + 1 < io_allowed) passed. > > Before this patch, in step 4) (io_disp + 1 < io_allowed) is passed, > because -90 for unsigned value is very huge, and such io won't be > throttled. > > Fix this problem by checking if 'io/bytes_allowed' is negative first. > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun
