On Tue, Dec 08, 2020 at 05:03:21PM +0100, Vincent Guittot wrote: > On Tue, 8 Dec 2020 at 16:35, Mel Gorman <mgor...@techsingularity.net> wrote: > > > > As noted by Vincent Guittot, avg_scan_costs are calculated for SIS_PROP > > even if SIS_PROP is disabled. Move the time calculations under a SIS_PROP > > check and while we are at it, exclude the cost of initialising the CPU > > mask from the average scan cost. > > > > Signed-off-by: Mel Gorman <mgor...@techsingularity.net> > > --- > > kernel/sched/fair.c | 14 ++++++++------ > > 1 file changed, 8 insertions(+), 6 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index ac7b34e7372b..5c41875aec23 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -6153,6 +6153,8 @@ static int select_idle_cpu(struct task_struct *p, > > struct sched_domain *sd, int t > > if (!this_sd) > > return -1; > > Just noticed while reviewing the patch that the above related to > this_sd can also go under sched_feat(SIS_PROP) >
Technically yes but I also decided against it. It's a functional difference depending on whether SIS_PROP is set in the highly unlikely case that this_sd == NULL. I was also thinking in terms of what happens if SIS_PROP was disabled and enabled while a search is in progress even if it's very unlikely. In that case, this_sd would be uninitialised. That might be impossible in practice depending on how static branching is implemented but I don't think we should rely on the internals of jump labels and play it safe. I can move it in if you feel strongly about it but I think the disable/enable race is enough of a concern to leave it alone. -- Mel Gorman SUSE Labs