On 01/07/2020 21:06, Valentin Schneider wrote: > I don't think it is going to change much in practice, but we were missing > those: > > o SD_BALANCE_WAKE: Used just like the other SD_BALANCE_* flags, so also > needs > 1 group. > o SD_ASYM_PACKING: Hinges on load balancing (periodic / wakeup), thus needs > > 1 group to happen > o SD_OVERLAP: Describes domains with overlapping groups; can't have > overlaps with a single group. > > SD_PREFER_SIBLING is as always the odd one out: we currently consider it > in sd_parent_degenerate() but not in sd_degenerate(). It too hinges on load > balancing, and thus won't have any effect when set on a domain with a > single group. Add it to the sd_degenerate() groups mask. > > Signed-off-by: Valentin Schneider <[email protected]> > --- > kernel/sched/topology.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index 6047d491abe9..fe393b295444 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -161,11 +161,15 @@ static int sd_degenerate(struct sched_domain *sd) > > /* Following flags need at least 2 groups */ > if (sd->flags & (SD_BALANCE_NEWIDLE | > + SD_BALANCE_WAKE | > SD_BALANCE_FORK | > SD_BALANCE_EXEC | > + SD_ASYM_PACKING | > SD_SHARE_CPUCAPACITY | > SD_ASYM_CPUCAPACITY | > - SD_SHARE_PKG_RESOURCES)) { > + SD_SHARE_PKG_RESOURCES | > + SD_OVERLAP | > + SD_PREFER_SIBLING)) {
Why do you add SD_PREFER_SIBLING here? It doesn't have SDF_NEEDS_GROUPS set in [PATCH v3 6/7]. $ cat ./include/linux/sched/sd_flags.h | grep ^SD_FLAG SD_FLAG(SD_BALANCE_NEWIDLE, 0, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) SD_FLAG(SD_BALANCE_EXEC, 1, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) SD_FLAG(SD_BALANCE_FORK, 2, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) SD_FLAG(SD_BALANCE_WAKE, 3, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) SD_FLAG(SD_WAKE_AFFINE, 4, SDF_SHARED_CHILD) SD_FLAG(SD_ASYM_CPUCAPACITY, 5, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) SD_FLAG(SD_SHARE_CPUCAPACITY, 6, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) SD_FLAG(SD_SHARE_PKG_RESOURCES, 7, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) SD_FLAG(SD_SERIALIZE, 8, SDF_SHARED_PARENT) SD_FLAG(SD_ASYM_PACKING, 9, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) SD_FLAG(SD_PREFER_SIBLING, 10, 0) <-- !!! SD_FLAG(SD_OVERLAP, 11, SDF_SHARED_PARENT |SDF_NEEDS_GROUPS) SD_FLAG(SD_NUMA, 12, SDF_SHARED_PARENT)
