Hello, On Thu, May 26, 2022 at 09:35:54PM +0800, Chengming Zhou wrote: > I found many false positive lagging during iocost test. > > Since iocg->vtime will be advanced to (vnow - margins.target) > in hweight_after_donation(), which called throw away excess, > the iocg->done_vtime will also be advanced that much. > > period_at_vtime <--period_vtime--> vnow > | | > ---------------------------------------------------> > |<--->| > margins.target > |-> > vtime, done_vtime All it does is shifting the vtime (and done_vtime) within the current window so that we don't build up budget too lage a budget possibly spanning multiple periods. The lagging detection is supposed to detect IOs which are issued two+ periods ago which didn't finish in the last period. So, I don't think the above sliding up the window affects that detection given that the lagging detection is done before the window sliding. All it's checking is whether there still are in-flight IOs which were issued two+ windows ago, so how the last window has been fast forwarded shouldn't affect the detection, no? Thanks. -- tejun
