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

From: Shrikanth Hegde
Date: Sat Mar 04 2023 - 10:13:43 EST

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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.
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?

>> 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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