* Peter Zijlstra <[email protected]> [2018-07-23 17:21:47]: > On Mon, Jul 23, 2018 at 08:09:55AM -0700, Srikar Dronamraju wrote: > > > > > sched/numa: Stop multiple tasks from moving to the cpu at the same > > > > time > > > > This patch has go-ahead from Mel and Rik and no outstanding comments. > > I left it out because it's part of the big xchg() mess. > > In particular: > > + if (xchg(&rq->numa_migrate_on, 1)) > + return; > + > + if (env->best_cpu != -1) { > + rq = cpu_rq(env->best_cpu); > + WRITE_ONCE(rq->numa_migrate_on, 0); > + } > > I'm again confused by clearing numa_migrate_on at this point..
First task choose a cpu to swap/migrate, sets the cpu to best_cpu and also numa_migrate_on. Next it finds a better cpu to swap/move. Now if the task is able to move to the better cpu, then it should clear numa_migrate_on on the previous best_cpu. If we dont reset numa_migrate_on on finding a better cpu, the numa_migrate_on stays set for the previous cpu, causing previous cpu to never be a target of numa balance. > > > > > sched/numa: Updation of scan period need not be in lock > > > > I didnt see any comments for this apart from an ack from Rik. > > + It thought it was trivial and shouldnt have any side-effect. > > Oh, my bad I actually have this one. >
