Messages in this thread | | | Subject | Re: [RFC PATCH] sched: fix the nonsense shares when load of cfs_rq is too, small | From | 王贇 <> | Date | Thu, 5 Mar 2020 09:14:47 +0800 |
| |
On 2020/3/5 上午2:47, bsegall@google.com wrote: [snip] >> Argh, because A->cfs_rq.load.weight is B->se.load.weight which is >> B->shares/nr_cpus. >> >>> While the se of D on root cfs_rq is far more bigger than 2, so it >>> wins the battle. >>> >>> This patch add a check on the zero load and make it as MIN_SHARES >>> to fix the nonsense shares, after applied the group C wins as >>> expected. >>> >>> Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com> >>> --- >>> kernel/sched/fair.c | 2 ++ >>> 1 file changed, 2 insertions(+) >>> >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>> index 84594f8aeaf8..53d705f75fa4 100644 >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -3182,6 +3182,8 @@ static long calc_group_shares(struct cfs_rq *cfs_rq) >>> tg_shares = READ_ONCE(tg->shares); >>> >>> load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg); >>> + if (!load && cfs_rq->load.weight) >>> + load = MIN_SHARES; >>> >>> tg_weight = atomic_long_read(&tg->load_avg); >> >> Yeah, I suppose that'll do. Hurmph, wants a comment though. >> >> But that has me looking at other users of scale_load_down(), and doesn't >> at least update_tg_cfs_load() suffer the same problem? > > I think instead we should probably scale_load_down(tg_shares) and > scale_load(load_avg). tg_shares is always a scaled integer, so just > moving the source of the scaling in the multiply should do the job. > > ie > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index fcc968669aea..6d7a9d72d742 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3179,9 +3179,9 @@ static long calc_group_shares(struct cfs_rq *cfs_rq) > long tg_weight, tg_shares, load, shares; > struct task_group *tg = cfs_rq->tg; > > - tg_shares = READ_ONCE(tg->shares); > + tg_shares = scale_load_down(READ_ONCE(tg->shares)); > > - load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg); > + load = max(cfs_rq->load.weight, scale_load(cfs_rq->avg.load_avg)); > > tg_weight = atomic_long_read(&tg->load_avg);
Get the point, but IMHO fix scale_load_down() sounds better, to cover all the similar cases, let's first try that way see if it's working :-)
Regards, Michael Wang
> > >
| |