On Wed, Oct 21, 2020 at 05:19:53PM +0200, Vincent Guittot wrote: > On Wed, 21 Oct 2020 at 17:08, Mel Gorman <mgorman@xxxxxxx> wrote: > > > > On Wed, Oct 21, 2020 at 03:24:48PM +0200, Julia Lawall wrote: > > > > I worry it's overkill because prev is always used if it is idle even > > > > if it is on a node remote to the waker. It cuts off the option of a > > > > wakee moving to a CPU local to the waker which is not equivalent to the > > > > original behaviour. > > > > > > But it is equal to the original behavior in the idle prev case if you go > > > back to the runnable load average days... > > > > > > > It is similar but it misses the sync treatment and sd->imbalance_pct part of > > wake_affine_weight which has unpredictable consequences. The data > > available is only on the fully utilised case. > > In fact It's the same because runnable_load_avg was null when cpu is idle, so > if prev_cpu was idle, we were selecting prev_idle > Sync wakeups may only consider this_cpu and the load of the waker but in that case, it was probably selected already by the sync check in wake_affine_idle which will pass except when the domain is overloaded. Fair enough, I'll withdraw any concerns. It could have done with a comment :/ -- Mel Gorman SUSE Labs
