Re: [PATCH v12 8/8] sched/fair: Add latency list

From: Vincent Guittot
Date: Sun Mar 05 2023 - 08:04:20 EST

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On Sat, 4 Mar 2023 at 16:13, Shrikanth Hegde <sshegde@xxxxxxxxxxxxxxxxxx> wrote:
>
>
>
> On 3/3/23 10:01 PM, Vincent Guittot wrote:
> > Le jeudi 02 mars 2023 à 23:37:52 (+0530), Shrikanth Hegde a écrit :
> >>
> >> On 3/2/23 8:30 PM, Shrikanth Hegde wrote:
> >>> On 3/2/23 6:47 PM, Vincent Guittot wrote:
> >>>> On Thu, 2 Mar 2023 at 12:00, Shrikanth Hegde <sshegde@xxxxxxxxxxxxxxxxxx> wrote:
> >>>>> On 3/2/23 1:20 PM, Vincent Guittot wrote:
> >>>>>> On Wed, 1 Mar 2023 at 19:48, shrikanth hegde <sshegde@xxxxxxxxxxxxxxxxxx> wrote:
> >>>>>>> On 2/24/23 3:04 PM, Vincent Guittot wrote:
> > [...]
> >
> >>>>>>> Ran the schbench and hackbench with this patch series. Here comparison is
> >>>>>>> between 6.2 stable tree, 6.2 + Patch and 6.2 + patch + above re-arrange of
> >>>>>>> latency_node. Ran two cgroups, in one cgroup running stress-ng at 50%(group1)
> >>>>>>> and other is running these benchmarks (group2). Set the latency nice
> >>>>>>> of group2 to -20. These are run on Power system with 12 cores with SMT=8.
> >>>>>>> Total of 96 CPU.
> >>>>>>>
> >>>>>>> schbench gets lower latency compared to stabletree. Whereas hackbench seems
> >>>>>>> to regress under this case. Maybe i am doing something wrong. I will re-run
> >>>>>>> and attach the numbers to series.
> >>>>>>> Please suggest if any variation in the test i need to try.
> >>>>>> hackbench takes advanatge of a latency nice 19 as it mainly wants to
> >>>>>> run longer slice to move forward rather than preempting others all the
> >>>>>> time
> >>>>> hackbench still seems to regress in different latency nice values compared to
> >>>>> baseline of 6.2 in this case. up to 50% in some cases.
> >>>>>
> >>>>> 12 core powerpc system with SMT=8 i.e 96 CPU
> >>>>> running 2 CPU cgroups. No quota assigned.
> >>>>> 1st cgroup is running stress-ng with 48 threads. Consuming 50% of CPU.
> >>>>> latency is not changed for this cgroup.
> >>>>> 2nd cgroup is running hackbench. This cgroup is assigned the different latency
> >>>>> nice values of 0, -20 and 19.
> >>>> According to your other emails, you are using the cgroup interface and
> >>>> not the task's one. Do I get it right ?
> >>> right. I create cgroup, attach bash command with echo $$,
> >>> assign the latency nice to cgroup, and run hackbench from that bash prompt.
> >>>
> >>>> I haven't run test such tests in a cgroup but at least the test with
> >>>> latency_nice == 0 should not make any noticeable difference. Does this
> >>>> include the re-arrange patch that you have proposed previously ?
> >>> No. This is only with V12 of the series.
> >>>
> >>>> Also, the tests that you did on v6, gave better result.
> >>>> https://lore.kernel.org/lkml/34112324-de67-55eb-92bc-181a98c4311c@xxxxxxxxxxxxxxxxxx/
> >>>>
> >>>> Are you running same tests or you changed something in the mean time ?
> >>> Test machine got changed.
> >>> now i re-read my earlier mail. I see it was slightly different.
> >>> I had created only one cgroup and stress-ng was run
> >>> without any cgroup. Let me try that scenario and get the numbers.
> >>
> >> Tried the same method of testing i had done on V7 of the series. on this
> >> machine hackbench still regress's both on V12 as well as V7 of the series.
> >>
> >> Created one cpu cgroup called cgroup1. created two bash prompts.
> >> assigned "bash $$" to cgroup1 and on other bash prompt running,
> >> stress-ng --cpu=96 -l 50. Ran hackbench from cgroup1 prompt.
> >> assigned latency values to the cgroup1.
> > I have tried to reproduce your results on some of my systems but I can't see
> > the impacts that you are reporting below.
> > The fact that your other platform was not impacted as well could imply that
> > it's specific to this platform.
> > In particular, the lat nice=0 case should not show any real impact as it
> > should be similar to a nop. At least that what I can see in the tests on my
> > platforms and Prateek on his.
> >
> > Nevertheless, could you try to run your tests with the changes below ?
> > These are the only places which could have an impact even with lat nice = 0
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 8137bca80572..979571a98b28 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4991,8 +4991,7 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
> > if (delta < offset)
> > return;
> >
> > - if ((delta > ideal_runtime) ||
> > - (delta > get_latency_max()))
> > + if (delta > ideal_runtime)
> > resched_curr(rq_of(cfs_rq));
> > }
> >
> > @@ -7574,9 +7573,10 @@ static long wakeup_latency_gran(struct sched_entity *curr, struct sched_entity *
> > * Otherwise, use the latency weight to evaluate how much scheduling
> > * delay is acceptable by se.
> > */
> > - if ((latency_offset < 0) || (curr->latency_offset < 0))
> > + if ((latency_offset < 0) || (curr->latency_offset < 0)) {
> > latency_offset -= curr->latency_offset;
> > - latency_offset = min_t(long, latency_offset, get_latency_max());
> > + latency_offset = min_t(long, latency_offset, get_latency_max());
> > + }
> >
> > return latency_offset;
> > }
> > @@ -7635,7 +7635,6 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
> > * for low priority task. Make sure that long sleeping task will get a
> > * chance to preempt current.
> > */
> > - gran = min_t(s64, gran, get_latency_max());
> >
> > if (vdiff > gran)
> > return 1;
> >
>
> Above patch helps. thank you.

Great. At least we have narrow the problem to one f the 3 changes.

> Numbers are comparable to 6.2 and there is slight improvement. Much better than V12 numbers.
>
> type groups | v6.2 |v6.2 + V12| v6.2 + V12 | v6.2 + V12
> | |lat nice=0| lat nice=-20| lat nice=+19
>
> Process 10 | 0.33 | 0.37 | 0.38 | 0.37
> Process 20 | 0.61 | 0.67 | 0.68 | 0.67
> Process 30 | 0.85 | 0.95 | 0.95 | 0.96
> Process 40 | 1.10 | 1.20 | 1.20 | 1.21
> Process 50 | 1.34 | 1.47 | 1.44 | 1.45
> Process 60 | 1.57 | 1.70 | 1.71 | 1.70
> thread 10 | 0.36 | 0.40 | 0.39 | 0.39
> thread 20 | 0.65 | 0.72 | 0.71 | 0.71
> Process(Pipe) 10 | 0.18 | 0.31 | 0.31 | 0.33
> Process(Pipe) 20 | 0.32 | 0.51 | 0.50 | 0.50
> Process(Pipe) 30 | 0.43 | 0.65 | 0.67 | 0.67
> Process(Pipe) 40 | 0.57 | 0.82 | 0.83 | 0.83
> Process(Pipe) 50 | 0.67 | 1.00 | 0.97 | 0.98
> Process(Pipe) 60 | 0.81 | 1.13 | 1.11 | 1.12
> thread(Pipe) 10 | 0.19 | 0.33 | 0.33 | 0.33
> thread(Pipe) 20 | 0.34 | 0.53 | 0.51 | 0.52
>
>
>
> type groups | v6.2 |v6.2+ V12+ | v6.2 + V12+| v6.2 + V12
> | |above patch|above patch | above patch
> | |lat nice=0 |lat nice=-20| lat nice=+19
>
> Process 10 | 0.36 | 0.33 | 0.34 | 0.34
> Process 20 | 0.62 | 0.60 | 0.61 | 0.61
> Process 30 | 0.87 | 0.84 | 0.85 | 0.84
> Process 40 | 1.13 | 1.09 | 1.10 | 1.09
> Process 50 | 1.38 | 1.33 | 1.33 | 1.34
> Process 60 | 1.64 | 1.56 | 1.58 | 1.56
> thread 10 | 0.35 | 0.35 | 0.35 | 0.35
> thread 20 | 0.64 | 0.63 | 0.63 | 0.63
> Process(Pipe) 10 | 0.20 | 0.18 | 0.18 | 0.18
> Process(Pipe) 20 | 0.32 | 0.31 | 0.31 | 0.32
> Process(Pipe) 30 | 0.44 | 0.43 | 0.43 | 0.43
> Process(Pipe) 40 | 0.56 | 0.57 | 0.56 | 0.55
> Process(Pipe) 50 | 0.70 | 0.67 | 0.67 | 0.67
> Process(Pipe) 60 | 0.83 | 0.79 | 0.81 | 0.80
> thread(Pipe) 10 | 0.21 | 0.19 | 0.19 | 0.19
> thread(Pipe) 20 | 0.35 | 0.33 | 0.34 | 0.33
>
>
> Do you want me to try any other experiment on this further?

Yes, would be good to know which of the 3 changes in the patch create
the regression

I suspect the 1st change to be the root cause of your problem but It
would be good if you can confirm my assumption with some tests

Thanks

>
> >> I will try to run with only task's set with latency_nice=0 as well.
> >>
> >> type groups | v6.2 |v6.2 + V12| v6.2 + V12 | v6.2 + V12
> >> | |lat nice=0| lat nice=-20| lat nice=+19
> >>
> >> Process 10 | 0.33 | 0.37 | 0.38 | 0.37
> >> Process 20 | 0.61 | 0.67 | 0.68 | 0.67
> >> Process 30 | 0.85 | 0.95 | 0.95 | 0.96
> >> Process 40 | 1.10 | 1.20 | 1.20 | 1.21
> >> Process 50 | 1.34 | 1.47 | 1.44 | 1.45
> >> Process 60 | 1.57 | 1.70 | 1.71 | 1.70
> >> thread 10 | 0.36 | 0.40 | 0.39 | 0.39
> >> thread 20 | 0.65 | 0.72 | 0.71 | 0.71
> >> Process(Pipe) 10 | 0.18 | 0.31 | 0.31 | 0.33
> >> Process(Pipe) 20 | 0.32 | 0.51 | 0.50 | 0.50
> >> Process(Pipe) 30 | 0.43 | 0.65 | 0.67 | 0.67
> >> Process(Pipe) 40 | 0.57 | 0.82 | 0.83 | 0.83
> >> Process(Pipe) 50 | 0.67 | 1.00 | 0.97 | 0.98
> >> Process(Pipe) 60 | 0.81 | 1.13 | 1.11 | 1.12
> >> thread(Pipe) 10 | 0.19 | 0.33 | 0.33 | 0.33
> >> thread(Pipe) 20 | 0.34 | 0.53 | 0.51 | 0.52
> >>
> >>
> >>
> >> type groups | v6.2 |v6.2 + V7 | v6.2 + V7 | v6.2 + V7
> >> | |lat nice=0|lat nice=-20| lat nice=+19
> >> Process 10 | 0.33 | 0.37 | 0.37 | 0.37
> >> Process 20 | 0.61 | 0.67 | 0.67 | 0.67
> >> Process 30 | 0.85 | 0.96 | 0.94 | 0.95
> >> Process 40 | 1.10 | 1.20 | 1.20 | 1.20
> >> Process 50 | 1.34 | 1.45 | 1.46 | 1.45
> >> Process 60 | 1.57 | 1.71 | 1.68 | 1.72
> >> thread 10 | 0.36 | 0.40 | 0.40 | 0.40
> >> thread 20 | 0.65 | 0.71 | 0.71 | 0.71
> >> Process(Pipe) 10 | 0.18 | 0.30 | 0.30 | 0.31
> >> Process(Pipe) 20 | 0.32 | 0.50 | 0.50 | 0.50
> >> Process(Pipe) 30 | 0.43 | 0.67 | 0.67 | 0.66
> >> Process(Pipe) 40 | 0.57 | 0.86 | 0.84 | 0.84
> >> Process(Pipe) 50 | 0.67 | 0.99 | 0.97 | 0.97
> >> Process(Pipe) 60 | 0.81 | 1.10 | 1.13 | 1.13
> >> thread(Pipe) 10 | 0.19 | 0.34 | 0.34 | 0.33
> >> thread(Pipe) 20 | 0.34 | 0.55 | 0.53 | 0.54
> >>
> >>>>> Numbers are average of 10 runs in each case. Time is in seconds
> >>>>>
> >>>>> type groups | v6.2 | v6.2 + V12 | v6.2 + V12 | v6.2 + V12
> >>>>> | | lat nice=0 | lat nice=-20| lat nice=+19
> >>>>> | | | |
> >>>>> Process 10 | 0.36 | 0.41 | 0.43 | 0.42
> >>>>> Process 20 | 0.62 | 0.76 | 0.75 | 0.75
> >>>>> Process 30 | 0.87 | 1.05 | 1.04 | 1.06
> >>>>> Process 40 | 1.13 | 1.34 | 1.33 | 1.33
> >>>>> Process 50 | 1.38 | 1.62 | 1.66 | 1.63
> >>>>> Process 60 | 1.64 | 1.91 | 1.97 | 1.90
> >>>>> thread 10 | 0.35 | 0.41 | 0.44 | 0.42
> >>>>> thread 20 | 0.64 | 0.78 | 0.77 | 0.79
> >>>>> Process(Pipe) 10 | 0.20 | 0.34 | 0.33 | 0.34
> >>>>> Process(Pipe) 20 | 0.32 | 0.52 | 0.53 | 0.52
> >>>>> Process(Pipe) 30 | 0.44 | 0.70 | 0.70 | 0.69
> >>>>> Process(Pipe) 40 | 0.56 | 0.88 | 0.89 | 0.88
> >>>>> Process(Pipe) 50 | 0.70 | 1.08 | 1.08 | 1.07
> >>>>> Process(Pipe) 60 | 0.83 | 1.27 | 1.27 | 1.26
> >>>>> thread(Pipe) 10 | 0.21 | 0.35 | 0.34 | 0.36
> >>>>> thread(Pipe) 10 | 0.35 | 0.55 | 0.58 | 0.55
> >>>>>
> >>>>>
> >>>>>
> >>>>>>> Re-arrange seems to help the patch series by avoiding an cacheline miss.
> >>>>>>>
> >>>>>>> =========================
> >>>>>>> schbench
> >>>>>>> =========================
> >>>>>>> 6.2 | 6.2 + V12 | 6.2 + V12 + re-arrange
> >>>>>>> 1 Thread
> >>>>>>> 50.0th: 9.00 | 9.00 | 9.50
> >>>>>>> 75.0th: 10.50 | 10.00 | 9.50
> >>>>>>> 90.0th: 11.00 | 11.00 | 10.50
> >>>>>>> 95.0th: 11.00 | 11.00 | 11.00
> >>>>>>> 99.0th: 11.50 | 11.50 | 11.50
> >>>>>>> 99.5th: 12.50 | 12.00 | 12.00
> >>>>>>> 99.9th: 14.50 | 13.50 | 12.00
> >>>>>>> 2 Threads
> >>>>>>> 50.0th: 9.50 | 9.50 | 8.50
> >>>>>>> 75.0th: 11.00 | 10.50 | 9.50
> >>>>>>> 90.0th: 13.50 | 11.50 | 10.50
> >>>>>>> 95.0th: 14.00 | 12.00 | 11.00
> >>>>>>> 99.0th: 15.50 | 13.50 | 12.00
> >>>>>>> 99.5th: 16.00 | 14.00 | 12.00
> >>>>>>> 99.9th: 17.00 | 16.00 | 16.50
> >>>>>>> 4 Threads
> >>>>>>> 50.0th: 11.50 | 11.50 | 10.50
> >>>>>>> 75.0th: 13.50 | 12.50 | 12.50
> >>>>>>> 90.0th: 15.50 | 14.50 | 14.00
> >>>>>>> 95.0th: 16.50 | 15.50 | 14.50
> >>>>>>> 99.0th: 20.00 | 17.50 | 16.50
> >>>>>>> 99.5th: 20.50 | 18.50 | 17.00
> >>>>>>> 99.9th: 22.50 | 21.00 | 19.00
> >>>>>>> 8 Threads
> >>>>>>> 50.0th: 14.00 | 14.00 | 14.00
> >>>>>>> 75.0th: 16.00 | 16.00 | 16.00
> >>>>>>> 90.0th: 18.00 | 18.00 | 17.50
> >>>>>>> 95.0th: 18.50 | 18.50 | 18.50
> >>>>>>> 99.0th: 20.00 | 20.00 | 20.00
> >>>>>>> 99.5th: 20.50 | 21.50 | 21.00
> >>>>>>> 99.9th: 22.50 | 23.50 | 23.00
> >>>>>>> 16 Threads
> >>>>>>> 50.0th: 19.00 | 18.50 | 19.00
> >>>>>>> 75.0th: 23.00 | 22.50 | 23.00
> >>>>>>> 90.0th: 25.00 | 25.50 | 25.00
> >>>>>>> 95.0th: 26.50 | 26.50 | 26.00
> >>>>>>> 99.0th: 28.50 | 29.00 | 28.50
> >>>>>>> 99.5th: 31.00 | 30.00 | 30.00
> >>>>>>> 99.9th: 5626.00 | 4761.50 | 32.50
> >>>>>>> 32 Threads
> >>>>>>> 50.0th: 27.00 | 27.50 | 29.00
> >>>>>>> 75.0th: 35.50 | 36.50 | 38.50
> >>>>>>> 90.0th: 42.00 | 44.00 | 50.50
> >>>>>>> 95.0th: 447.50 | 2959.00 | 8544.00
> >>>>>>> 99.0th: 7372.00 | 17032.00 | 19136.00
> >>>>>>> 99.5th: 15360.00 | 19808.00 | 20704.00
> >>>>>>> 99.9th: 20640.00 | 30048.00 | 30048.00
> >>>>>>>
> >>>>>>> ====================
> >>>>>>> hackbench
> >>>>>>> ====================
> >>>>>>> 6.2 | 6.2 + V12 | 6.2+ V12 +re-arrange
> >>>>>>>
> >>>>>>> Process 10 Time: 0.35 | 0.42 | 0.41
> >>>>>>> Process 20 Time: 0.61 | 0.76 | 0.76
> >>>>>>> Process 30 Time: 0.87 | 1.06 | 1.05
> >>>>>>> thread 10 Time: 0.35 | 0.43 | 0.42
> >>>>>>> thread 20 Time: 0.66 | 0.79 | 0.78
> >>>>>>> Process(Pipe) 10 Time: 0.21 | 0.33 | 0.32
> >>>>>>> Process(Pipe) 20 Time: 0.34 | 0.52 | 0.52
> >>>>>>> Process(Pipe) 30 Time: 0.46 | 0.72 | 0.71
> >>>>>>> thread(Pipe) 10 Time: 0.21 | 0.34 | 0.34
> >>>>>>> thread(Pipe) 20 Time: 0.36 | 0.56 | 0.56
> >>>>>>>
> >>>>>>>
> >>>>>>>> struct list_head group_node;
> >>>>>>>> unsigned int on_rq;
> >>>>>>>>
> >>>>>>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> >>>>>>>> index 093cc1af73dc..752fd364216c 100644
> >>>>>>>> --- a/kernel/sched/core.c
> >>>>>>>> +++ b/kernel/sched/core.c
> >>>>>>>> @@ -4434,6 +4434,7 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
> >>>>>>>> p->se.nr_migrations = 0;
> >>>>>>>> p->se.vruntime = 0;
> >>>>>>>> INIT_LIST_HEAD(&p->se.group_node);
> >>>>>>>> + RB_CLEAR_NODE(&p->se.latency_node);
> >>>>>>>>
> >>>>>>>> #ifdef CONFIG_FAIR_GROUP_SCHED
> >>>>>>>> p->se.cfs_rq = NULL;
> >>>>>>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> >>>>>>>> index 125a6ff53378..e2aeb4511686 100644
> >>>>>>>> --- a/kernel/sched/fair.c
> >>>>>>>> +++ b/kernel/sched/fair.c
> >>>>>>>> @@ -680,7 +680,85 @@ struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
> >>>>>>>>
> >>>>>>>> return __node_2_se(last);
> >>>>>>>> }
> >>>>>>>> +#endif
> >>>>>>>>
> >>>>>>>> +/**************************************************************
> >>>>>>>> + * Scheduling class tree data structure manipulation methods:
> >>>>>>>> + * for latency
> >>>>>>>> + */
> >>>>>>>> +
> >>>>>>>> +static inline bool latency_before(struct sched_entity *a,
> >>>>>>>> + struct sched_entity *b)
> >>>>>>>> +{
> >>>>>>>> + return (s64)(a->vruntime + a->latency_offset - b->vruntime - b->latency_offset) < 0;
> >>>>>>>> +}
> >>>>>>>> +
> >>>>>>>> +#define __latency_node_2_se(node) \
> >>>>>>>> + rb_entry((node), struct sched_entity, latency_node)
> >>>>>>>> +
> >>>>>>>> +static inline bool __latency_less(struct rb_node *a, const struct rb_node *b)
> >>>>>>>> +{
> >>>>>>>> + return latency_before(__latency_node_2_se(a), __latency_node_2_se(b));
> >>>>>>>> +}
> >>>>>>>> +
> >>>>>>>> +/*
> >>>>>>>> + * Enqueue an entity into the latency rb-tree:
> >>>>>>>> + */
> >>>>>>>> +static void __enqueue_latency(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> >>>>>>>> +{
> >>>>>>>> +
> >>>>>>>> + /* Only latency sensitive entity can be added to the list */
> >>>>>>>> + if (se->latency_offset >= 0)
> >>>>>>>> + return;
> >>>>>>>> +
> >>>>>>>> + if (!RB_EMPTY_NODE(&se->latency_node))
> >>>>>>>> + return;
> >>>>>>>> +
> >>>>>>>> + /*
> >>>>>>>> + * The entity is always added the latency list at wakeup.
> >>>>>>>> + * Then, a not waking up entity that is put back in the list after an
> >>>>>>>> + * execution time less than sysctl_sched_min_granularity, means that
> >>>>>>>> + * the entity has been preempted by a higher sched class or an entity
> >>>>>>>> + * with higher latency constraint. In thi case, the entity is also put
> >>>>>>>> + * back in the latency list so it gets a chance to run 1st during the
> >>>>>>>> + * next slice.
> >>>>>>>> + */
> >>>>>>>> + if (!(flags & ENQUEUE_WAKEUP)) {
> >>>>>>>> + u64 delta_exec = se->sum_exec_runtime - se->prev_sum_exec_runtime;
> >>>>>>>> +
> >>>>>>>> + if (delta_exec >= sysctl_sched_min_granularity)
> >>>>>>>> + return;
> >>>>>>>> + }
> >>>>>>>> +
> >>>>>>>> + rb_add_cached(&se->latency_node, &cfs_rq->latency_timeline, __latency_less);
> >>>>>>>> +}
> >>>>>>>> +
> >>>>>>>> +/*
> >>>>>>>> + * Dequeue an entity from the latency rb-tree and return true if it was really
> >>>>>>>> + * part of the rb-tree:
> >>>>>>>> + */
> >>>>>>>> +static bool __dequeue_latency(struct cfs_rq *cfs_rq, struct sched_entity *se)
> >>>>>>>> +{
> >>>>>>>> + if (!RB_EMPTY_NODE(&se->latency_node)) {
> >>>>>>>> + rb_erase_cached(&se->latency_node, &cfs_rq->latency_timeline);
> >>>>>>>> + RB_CLEAR_NODE(&se->latency_node);
> >>>>>>>> + return true;
> >>>>>>>> + }
> >>>>>>>> +
> >>>>>>>> + return false;
> >>>>>>>> +}
> >>>>>>>> +
> >>>>>>>> +static struct sched_entity *__pick_first_latency(struct cfs_rq *cfs_rq)
> >>>>>>>> +{
> >>>>>>>> + struct rb_node *left = rb_first_cached(&cfs_rq->latency_timeline);
> >>>>>>>> +
> >>>>>>>> + if (!left)
> >>>>>>>> + return NULL;
> >>>>>>>> +
> >>>>>>>> + return __latency_node_2_se(left);
> >>>>>>>> +}
> >>>>>>>> +
> >>>>>>>> +#ifdef CONFIG_SCHED_DEBUG
> >>>>>>>> /**************************************************************
> >>>>>>>> * Scheduling class statistics methods:
> >>>>>>>> */
> >>>>>>>> @@ -4758,8 +4836,10 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> >>>>>>>> check_schedstat_required();
> >>>>>>>> update_stats_enqueue_fair(cfs_rq, se, flags);
> >>>>>>>> check_spread(cfs_rq, se);
> >>>>>>>> - if (!curr)
> >>>>>>>> + if (!curr) {
> >>>>>>>> __enqueue_entity(cfs_rq, se);
> >>>>>>>> + __enqueue_latency(cfs_rq, se, flags);
> >>>>>>>> + }
> >>>>>>>> se->on_rq = 1;
> >>>>>>>>
> >>>>>>>> if (cfs_rq->nr_running == 1) {
> >>>>>>>> @@ -4845,8 +4925,10 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> >>>>>>>>
> >>>>>>>> clear_buddies(cfs_rq, se);
> >>>>>>>>
> >>>>>>>> - if (se != cfs_rq->curr)
> >>>>>>>> + if (se != cfs_rq->curr) {
> >>>>>>>> __dequeue_entity(cfs_rq, se);
> >>>>>>>> + __dequeue_latency(cfs_rq, se);
> >>>>>>>> + }
> >>>>>>>> se->on_rq = 0;
> >>>>>>>> account_entity_dequeue(cfs_rq, se);
> >>>>>>>>
> >>>>>>>> @@ -4941,6 +5023,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
> >>>>>>>> */
> >>>>>>>> update_stats_wait_end_fair(cfs_rq, se);
> >>>>>>>> __dequeue_entity(cfs_rq, se);
> >>>>>>>> + __dequeue_latency(cfs_rq, se);
> >>>>>>>> update_load_avg(cfs_rq, se, UPDATE_TG);
> >>>>>>>> }
> >>>>>>>>
> >>>>>>>> @@ -4979,7 +5062,7 @@ static struct sched_entity *
> >>>>>>>> pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
> >>>>>>>> {
> >>>>>>>> struct sched_entity *left = __pick_first_entity(cfs_rq);
> >>>>>>>> - struct sched_entity *se;
> >>>>>>>> + struct sched_entity *latency, *se;
> >>>>>>>>
> >>>>>>>> /*
> >>>>>>>> * If curr is set we have to see if its left of the leftmost entity
> >>>>>>>> @@ -5021,6 +5104,12 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
> >>>>>>>> se = cfs_rq->last;
> >>>>>>>> }
> >>>>>>>>
> >>>>>>>> + /* Check for latency sensitive entity waiting for running */
> >>>>>>>> + latency = __pick_first_latency(cfs_rq);
> >>>>>>>> + if (latency && (latency != se) &&
> >>>>>>>> + wakeup_preempt_entity(latency, se) < 1)
> >>>>>>>> + se = latency;
> >>>>>>>> +
> >>>>>>>> return se;
> >>>>>>>> }
> >>>>>>>>
> >>>>>>>> @@ -5044,6 +5133,7 @@ static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
> >>>>>>>> update_stats_wait_start_fair(cfs_rq, prev);
> >>>>>>>> /* Put 'current' back into the tree. */
> >>>>>>>> __enqueue_entity(cfs_rq, prev);
> >>>>>>>> + __enqueue_latency(cfs_rq, prev, 0);
> >>>>>>>> /* in !on_rq case, update occurred at dequeue */
> >>>>>>>> update_load_avg(cfs_rq, prev, 0);
> >>>>>>>> }
> >>>>>>>> @@ -12222,6 +12312,7 @@ static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
> >>>>>>>> void init_cfs_rq(struct cfs_rq *cfs_rq)
> >>>>>>>> {
> >>>>>>>> cfs_rq->tasks_timeline = RB_ROOT_CACHED;
> >>>>>>>> + cfs_rq->latency_timeline = RB_ROOT_CACHED;
> >>>>>>>> u64_u32_store(cfs_rq->min_vruntime, (u64)(-(1LL << 20)));
> >>>>>>>> #ifdef CONFIG_SMP
> >>>>>>>> raw_spin_lock_init(&cfs_rq->removed.lock);
> >>>>>>>> @@ -12378,6 +12469,7 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
> >>>>>>>> se->my_q = cfs_rq;
> >>>>>>>>
> >>>>>>>> se->latency_offset = calc_latency_offset(tg->latency_prio);
> >>>>>>>> + RB_CLEAR_NODE(&se->latency_node);
> >>>>>>>>
> >>>>>>>> /* guarantee group entities always have weight */
> >>>>>>>> update_load_set(&se->load, NICE_0_LOAD);
> >>>>>>>> @@ -12529,8 +12621,19 @@ int sched_group_set_latency(struct task_group *tg, int prio)
> >>>>>>>>
> >>>>>>>> for_each_possible_cpu(i) {
> >>>>>>>> struct sched_entity *se = tg->se[i];
> >>>>>>>> + struct rq *rq = cpu_rq(i);
> >>>>>>>> + struct rq_flags rf;
> >>>>>>>> + bool queued;
> >>>>>>>> +
> >>>>>>>> + rq_lock_irqsave(rq, &rf);
> >>>>>>>>
> >>>>>>>> + queued = __dequeue_latency(se->cfs_rq, se);
> >>>>>>>> WRITE_ONCE(se->latency_offset, latency_offset);
> >>>>>>>> + if (queued)
> >>>>>>>> + __enqueue_latency(se->cfs_rq, se, ENQUEUE_WAKEUP);
> >>>>>>>> +
> >>>>>>>> +
> >>>>>>>> + rq_unlock_irqrestore(rq, &rf);
> >>>>>>>> }
> >>>>>>>>
> >>>>>>>> mutex_unlock(&shares_mutex);
> >>>>>>>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> >>>>>>>> index 9a2e71231083..21dd309e98a9 100644
> >>>>>>>> --- a/kernel/sched/sched.h
> >>>>>>>> +++ b/kernel/sched/sched.h
> >>>>>>>> @@ -570,6 +570,7 @@ struct cfs_rq {
> >>>>>>>> #endif
> >>>>>>>>
> >>>>>>>> struct rb_root_cached tasks_timeline;
> >>>>>>>> + struct rb_root_cached latency_timeline;
> >>>>>>>>
> >>>>>>>> /*
> >>>>>>>> * 'curr' points to currently running entity on this cfs_rq.
>

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