Ming Lei <ming.lei@xxxxxxxxxx> writes: > From: David Jeffery <djeffery@xxxxxxxxxx> > > Current code supposes that it is enough to provide forward progress by just > waking up one wait queue after one completion batch is done. > > Unfortunately this way isn't enough, cause waiter can be added to > wait queue just after it is woken up. > > Follows one example(64 depth, wake_batch is 8) > > 1) all 64 tags are active > > 2) in each wait queue, there is only one single waiter > > 3) each time one completion batch(8 completions) wakes up just one waiter in each wait > queue, then immediately one new sleeper is added to this wait queue > > 4) after 64 completions, 8 waiters are wakeup, and there are still 8 waiters in each > wait queue > > 5) after another 8 active tags are completed, only one waiter can be wakeup, and the other 7 > can't be waken up anymore. > > Turns out it isn't easy to fix this problem, so simply wakeup enough waiters for > single batch. yes, I think this makes sense. When working on this algorithm I remember I considered it (thus wake_up_nr being ready), but ended up believing it wasn't needed. please take: Reviewed-by: Gabriel Krisman Bertazi <krisman@xxxxxxx> I wonder how likely it is to reach it. Did you get a bug report? Thanks, -- Gabriel Krisman Bertazi
