On Mon, Dec 19, 2016 at 2:40 PM, Samuel Thibault <[email protected]> wrote: > 2159197d6677 ("sched/core: Enable increased load resolution on 64-bit > kernels") > > exposed yet another miscalculation in calc_cfs_shares: MIN_SHARES is unscaled, > and must thus be scaled before being manipulated against "shares" amounts.
It's actually intentional that MIN_SHARES is un-scaled here, this is necessary to support the goal of sub-partitioning groups with small shares. E.g. A group with shares=2 and 5 threads will internally provide 2048 units of weight for the load-balancer to account for their distribution. > > Signed-off-by: Samuel Thibault <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: [email protected] > Fixes: 2159197d6677 ("sched/core: Enable increased load resolution on 64-bit > kernels") > > --- > This should be backported to 4.7 and 4.8 to fix scheduling priorities > miscalculations > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 6559d19..be84f72 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2657,8 +2657,8 @@ static long calc_cfs_shares(struct cfs_rq *cfs_rq, > struct task_group *tg) > if (tg_weight) > shares /= tg_weight; > > - if (shares < MIN_SHARES) > - shares = MIN_SHARES; > + if (shares < scale_load(MIN_SHARES)) > + shares = scale_load(MIN_SHARES); > if (shares > tg->shares) > shares = tg->shares; >
