On Wed, Jul 11, 2018 at 10:43:28AM +0200, Dietmar Eggemann wrote: > On 07/11/2018 01:09 AM, Joel Fernandes wrote: > > On Mon, Jul 09, 2018 at 05:47:53PM +0100, Dietmar Eggemann wrote: > > > A CFS (SCHED_OTHER, SCHED_BATCH or SCHED_IDLE policy) task's > > > se->runnable_weight must always be in sync with its se->load.weight. > > > > > > se->runnable_weight is set to se->load.weight when the task is > > > forked (init_entity_runnable_average()) or reniced (reweight_entity()). > > > > > > There are two cases in set_load_weight() which since they currently only > > > set se->load.weight could lead to a situation in which se->load.weight > > > is different to se->runnable_weight for a CFS task: > > > > > > (1) A task switches to SCHED_IDLE. > > > > > > (2) A SCHED_FIFO, SCHED_RR or SCHED_DEADLINE task which has been reniced > > > (during which only its static priority gets set) switches to > > > SCHED_OTHER or SCHED_BATCH. > > > > > > Set se->runnable_weight to se->load.weight in these two cases to prevent > > > this. This eliminates the need to explicitly set it to se->load.weight > > > during PELT updates in the CFS scheduler fastpath. > > > > Looks good to me. By the way just asking, is there a chance where > > se_weight(se) and se_runnable(se) can ever be different? > > Yes they can be different, not for a task though but for se's representing > task groups. It got introduced to be able to propagate load and runnable > load independently through the task groups hierarchies.
I know that task-group se has different values. I was saying for task ses, the extra division can be skipped possibly improving performance (if at all). thanks, - Joel