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Message-ID: <2226e488-390d-ed64-832e-ca8e6a3a1731@linux.vnet.ibm.com>
Date: Thu, 2 Mar 2023 23:37:52 +0530
From: Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: qyousef@...alina.io, chris.hyser@...cle.com,
patrick.bellasi@...bug.net, David.Laight@...lab.com,
pjt@...gle.com, pavel@....cz, qperret@...gle.com,
tim.c.chen@...ux.intel.com, joshdon@...gle.com, timj@....org,
kprateek.nayak@....com, yu.c.chen@...el.com,
youssefesmat@...omium.org, joel@...lfernandes.org,
mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
linux-kernel@...r.kernel.org, parth@...ux.ibm.com, tj@...nel.org,
lizefan.x@...edance.com, hannes@...xchg.org,
cgroups@...r.kernel.org, corbet@....net, linux-doc@...r.kernel.org,
Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>
Subject: Re: [PATCH v12 8/8] sched/fair: Add latency list
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@...ux.vnet.ibm.com> wrote:
>>> On 3/2/23 1:20 PM, Vincent Guittot wrote:
>>>> On Wed, 1 Mar 2023 at 19:48, shrikanth hegde <sshegde@...ux.vnet.ibm.com> wrote:
>>>>> On 2/24/23 3:04 PM, Vincent Guittot wrote:
>>>>>> Add a rb tree for latency sensitive entities so we can schedule the most
>>>>>> sensitive one first even when it failed to preempt current at wakeup or
>>>>>> when it got quickly preempted by another entity of higher priority.
>>>>>>
>>>>>> In order to keep fairness, the latency is used once at wakeup to get a
>>>>>> minimum slice and not during the following scheduling slice to prevent
>>>>>> long running entity to got more running time than allocated to his nice
>>>>>> priority.
>>>>>>
>>>>>> The rb tree enables to cover the last corner case where latency
>>>>>> sensitive entity can't got schedule quickly after the wakeup.
>>>>>>
>>>>>> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
>>>>>> Tested-by: K Prateek Nayak <kprateek.nayak@....com>
>>>>>> ---
>>>>>> include/linux/sched.h | 1 +
>>>>>> kernel/sched/core.c | 1 +
>>>>>> kernel/sched/fair.c | 109 ++++++++++++++++++++++++++++++++++++++++--
>>>>>> kernel/sched/sched.h | 1 +
>>>>>> 4 files changed, 109 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>>>>>> index 38decae3e156..41bb92be5ecc 100644
>>>>>> --- a/include/linux/sched.h
>>>>>> +++ b/include/linux/sched.h
>>>>>> @@ -548,6 +548,7 @@ struct sched_entity {
>>>>>> /* For load-balancing: */
>>>>>> struct load_weight load;
>>>>>> struct rb_node run_node;
>>>>>> + struct rb_node latency_node;
>>>>> Ran pahole to see if the frequently accessed fields change across cachelines.
>>>>> There is no change in cachelines of task_struct, whereas sched_entity differs
>>>>> due to latency_node. Maybe the latency_node could be placed after
>>>>> runnable_weight as there is space available in that cacheline.
>>>> I will run some test on my system to confimr your results but we can
>>>> move latency_node field if it helps cache hit stats
>>>>
>>>>> 6.2
>>>>> #pahole sched_entity
>>>>> struct sched_entity {
>>>>> struct load_weight load; /* 0 16 */
>>>>>
>>>>> /* XXX last struct has 4 bytes of padding */
>>>>>
>>>>> struct rb_node run_node; /* 16 24 */
>>>>> struct list_head group_node; /* 40 16 */
>>>>> unsigned int on_rq; /* 56 4 */
>>>>>
>>>>> /* XXX 4 bytes hole, try to pack */
>>>>>
>>>>> u64 exec_start; /* 64 8 */
>>>>> u64 sum_exec_runtime; /* 72 8 */
>>>>> u64 vruntime; /* 80 8 */
>>>>> u64 prev_sum_exec_runtime; /* 88 8 */
>>>>> u64 nr_migrations; /* 96 8 */
>>>>> int depth; /* 104 4 */
>>>>>
>>>>> /* XXX 4 bytes hole, try to pack */
>>>>>
>>>>> struct sched_entity * parent; /* 112 8 */
>>>>> struct cfs_rq * cfs_rq; /* 120 8 */
>>>>> /* --- cacheline 1 boundary (128 bytes) --- */
>>>>> struct cfs_rq * my_q; /* 128 8 */
>>>>> long unsigned int runnable_weight; /* 136 8 */
>>>>>
>>>>> /* XXX 112 bytes hole, try to pack */
>>>>>
>>>>> /* --- cacheline 2 boundary (256 bytes) --- */
>>>>> struct sched_avg avg; /* 256 128 */
>>>>>
>>>>>
>>>>> 6.2 + V12 patch
>>>>> #pahole sched_entity
>>>>> struct sched_entity {
>>>>> struct load_weight load; /* 0 16 */
>>>>>
>>>>> /* XXX last struct has 4 bytes of padding */
>>>>>
>>>>> struct rb_node run_node; /* 16 24 */
>>>>> struct rb_node latency_node; /* 40 24 */
>>>>> struct list_head group_node; /* 64 16 */
>>>>> unsigned int on_rq; /* 80 4 */
>>>>>
>>>>> /* XXX 4 bytes hole, try to pack */
>>>>>
>>>>> u64 exec_start; /* 88 8 */
>>>>> u64 sum_exec_runtime; /* 96 8 */
>>>>> u64 vruntime; /* 104 8 */
>>>>> u64 prev_sum_exec_runtime; /* 112 8 */
>>>>> u64 nr_migrations; /* 120 8 */
>>>>> /* --- cacheline 1 boundary (128 bytes) --- */
>>>>> int depth; /* 128 4 */
>>>>>
>>>>> /* XXX 4 bytes hole, try to pack */
>>>>>
>>>>> struct sched_entity * parent; /* 136 8 */
>>>>> struct cfs_rq * cfs_rq; /* 144 8 */
>>>>> struct cfs_rq * my_q; /* 152 8 */
>>>>>
>>>>>
>>>>> 6.2 + V12 patch + Re-shuffle of latency_node
>>>>> #pahole sched_entity
>>>>> struct sched_entity {
>>>>> struct load_weight load; /* 0 16 */
>>>>>
>>>>> /* XXX last struct has 4 bytes of padding */
>>>>>
>>>>> struct rb_node run_node; /* 16 24 */
>>>>> struct list_head group_node; /* 40 16 */
>>>>> unsigned int on_rq; /* 56 4 */
>>>>>
>>>>> /* XXX 4 bytes hole, try to pack */
>>>>>
>>>>> u64 exec_start; /* 64 8 */
>>>>> u64 sum_exec_runtime; /* 72 8 */
>>>>> u64 vruntime; /* 80 8 */
>>>>> u64 prev_sum_exec_runtime; /* 88 8 */
>>>>> u64 nr_migrations; /* 96 8 */
>>>>> int depth; /* 104 4 */
>>>>>
>>>>> /* XXX 4 bytes hole, try to pack */
>>>>>
>>>>> struct sched_entity * parent; /* 112 8 */
>>>>> struct cfs_rq * cfs_rq; /* 120 8 */
>>>>> /* --- cacheline 1 boundary (128 bytes) --- */
>>>>> struct cfs_rq * my_q; /* 128 8 */
>>>>> long unsigned int runnable_weight; /* 136 8 */
>>>>> struct rb_node latency_node; /* 144 24 */
>>>>> long int latency_offset; /* 168 8 */
>>>>>
>>>>> /* XXX 80 bytes hole, try to pack */
>>>>>
>>>>> /* --- cacheline 2 boundary (256 bytes) --- */
>>>>>
>>>>>
>>>>>
>>>>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>>>>> index a2b52cf5e1bb..1e93aaaeead2 100644
>>>>> --- a/include/linux/sched.h
>>>>> +++ b/include/linux/sched.h
>>>>> @@ -548,7 +548,6 @@ struct sched_entity {
>>>>> /* For load-balancing: */
>>>>> struct load_weight load;
>>>>> struct rb_node run_node;
>>>>> - struct rb_node latency_node;
>>>>> struct list_head group_node;
>>>>> unsigned int on_rq;
>>>>>
>>>>> @@ -569,6 +568,7 @@ struct sched_entity {
>>>>> /* cached value of my_q->h_nr_running */
>>>>> unsigned long runnable_weight;
>>>>> #endif
>>>>> + struct rb_node latency_node;
>>>>> /* preemption offset in ns */
>>>>> long latency_offset;
>>>>>
>>>>>
>>>>> 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 $$,
> assign the latency nice to cgroup, and run hackbench from that bash prompt.
>
>> I haven't run test such tests in a cgroup but at least the test with
>> latency_nice == 0 should not make any noticeable difference. Does this
>> include the re-arrange patch that you have proposed previously ?
> No. This is only with V12 of the series.
>
>> Also, the tests that you did on v6, gave better result.
>> https://lore.kernel.org/lkml/34112324-de67-55eb-92bc-181a98c4311c@linux.vnet.ibm.com/
>>
>> Are you running same tests or you changed something in the mean time ?
> Test machine got changed.
> now i re-read my earlier mail. I see it was slightly different.
> I had created only one cgroup and stress-ng was run
> without any cgroup. Let me try that scenario and get the numbers.
Tried the same method of testing i had done on V7 of the series. on this
machine hackbench still regress's both on V12 as well as V7 of the series.
Created one cpu cgroup called cgroup1. created two bash prompts.
assigned "bash $$" 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 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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