On Mon, May 30, 2016 at 03:37:48PM +0200, Sebastian Andrzej Siewior wrote: > Yes, I did not try to discuss the hash collision away. From RT's point > of view the problems I am aware are of the following scenario: > Task #1 pinned to CPU1 task #2 pinned to CPU2 but share the same > bucket. Task #2 got a wakeup and should run but is blocked on the > bucket lock - otherwise it could run. Usually it would PI-boost task#1 > but task#1 got preempted itself by task and since task#1 prio is lower > it can't boost its way free towards the lock and so so CPU #2 may > remain idle for some time. > > The same thing can happen within a Task if you take my story from above > and replace task with thread. Completely understood.
Right; so I don't see the point of PREALLOCATE_HASH to cater for RT workloads if it still doesn't guarantee anything, esp. if the failure case is silent and obscure.
