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description/scheduler: Capacity Aware Scheduling
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Cheng Jian
@@ -1230,7 +1230,7 @@ Mike Galbraith 调试发现, 触发这个问题的原因是因为 wake_affine_we
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>
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>[Another attempt at power-aware scheduling](https://lwn.net/Articles/600419)
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### 7.2.2 IKS -> HMP -> EAS
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### 7.2.2 IKS -> HMP -> EAS & CAS
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@@ -1249,32 +1249,63 @@ ARM 的 Morten Rasmussen 一直致力于ANDROID 调度器优化的:
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5. EAS 带来了划时代的想法, 最终 [Quentin Perret](http://www.linux-arm.org/git?p=linux-qp.git;a=summary) 接手了 Morten Rasmussen 的工作, 最终在 2018/10/03 v10 版本将 EAS 合入主线 [https://lore.kernel.org/patchwork/cover/1020432/](https://lore.kernel.org/patchwork/cover/1020432)
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### 7.2.3 异构调度优化
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6. EAS 并不适用于所有场景,
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### 7.2.3 EAS(Energy Aware Scheduling)
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-------
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后续基于 EAS 还做了很多优化
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| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
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|:----:|:----:|:---:|:---:|:----------:|:----:|
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| 2018/12/03 | Quentin Perret | [Energy Aware Scheduling](https://lore.kernel.org/patchwork/cover/1020432) | 能效感知的调度器 EAS | v10 ☑ 5.0-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1020432) |
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| 2019/08/22 | Patrick Bellasi | [Add utilization clamping support (CGroups API)](https://lore.kernel.org/patchwork/cover/1118345) | TASK util clamp(Android schedtune 的主线替代方案) | v14 ☑ 5.4-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1118345) |
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| 2021/12/20 | Vincent Donnefort <vincent.donnefort@arm.com> | [Fix stuck overutilized](https://lkml.kernel.org/lkml/20211220114323.22811-1-vincent.donnefort@arm.com) | NA | v1 ☐ | [LORE 0/3](https://lkml.kernel.org/lkml/20211220114323.22811-1-vincent.donnefort@arm.com) |
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### 7.2.4 CAS(Capacity Aware Scheduling)
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-------
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在支持 misfit task 的过程中, [commit df054e8445a4 ("sched/topology: Add static_key for asymmetric CPU capacity optimizations")](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=df054e8445a4011e3d693c2268129c0456108663) 引入了 sched_asym_cpucapacity static_key, 来控制 CAS(Capacity Aware Scheduling).
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在整个调度域过载(sd->overutilized) 的时候, 内核将禁用 EAS, 选择使用 CAS 来作为异构平台的首选调度器. CAS 的思路很简单, 通过 task_fits_capacity() 判断当前调度域或者 CPU 的 capacity 是否能满足当前进程的要求, 然后尽可能为进程选择 capacity 满足要求的 CPU.
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* capacity asymmetry detection
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| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
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|:----:|:----:|:---:|:---:|:----------:|:----:|
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| 2016/10/14 | Vincent Guittot | [sched: Clean-ups and asymmetric cpu capacity support](https://lore.kernel.org/patchwork/cover/725608) | 调度程序目前在非对称计算能力的系统上没有做太多的工作来提高性能(读ARM big.LITTLE). 本系列主要通过对任务唤醒路径进行一些调整来改善这种情况, 这些调整主要考虑唤醒时的计算容量, 而不仅仅考虑cpu对这些系统是否空闲. 在部分使用的场景中, 这为我们提供了一致的、可能更高的吞吐量. SMP的行为和性能应该是不受影响. <br>注意这组补丁是分批合入的 | v1 ☑ 4.10-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/725608) |
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| 2018/03/15 | Morten Rasmussen | [sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems](https://lore.kernel.org/patchwork/cover/933989) | 异构 CPU 上 wakeup 路径倾向于使用 prev CPU | v1 ☑ 4.20-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/933989) |
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| 2018/12/03 | Quentin Perret | [Energy Aware Scheduling](https://lore.kernel.org/patchwork/cover/1020432) | 能效感知的调度器 EAS | v10 ☑ 5.0-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1020432) |
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| 2019/08/22 | Patrick Bellasi | [Add utilization clamping support (CGroups API)](https://lore.kernel.org/patchwork/cover/1118345) | TASK util clamp(Android schedtune 的主线替代方案) | v14 ☑ 5.4-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1118345) |
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| 2020/02/06 | Vincent Guittot | [sched/fair: Capacity aware wakeup rework](https://lore.kernel.org/patchwork/cover/1190300) | 异构 CPU 上 wakeup 路径优化 | v4 ☑ 5.7-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1190300) |
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| 2020/05/20 | Dietmar Eggemann | [Capacity awareness for SCHED_DEADLINE](https://lore.kernel.org/patchwork/cover/1245028) | DEADLINE 感知 Capacity | v3 ☐ 5.9-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1245028) |
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| 2020/12/19 | Vincent Guittot | [sched/fair: prefer prev cpu in asymmetric wakeup path](https://lore.kernel.org/patchwork/cover/1329119) | 异构 CPU 上 wakeup 路径倾向于使用 prev CPU | v1 ☑ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1308748) |
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| 2021/03/11 | Valentin Schneider | [sched/fair: misfit task load-balance tweaks](https://lore.kernel.org/patchwork/cover/1393531) | 优化 misfit task 的一些逻辑 | v3 ☐ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1393531) |
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| 2021/04/07 | Valentin Schneider | [sched/fair: load-balance vs capacity margins](https://lore.kernel.org/patchwork/cover/1409479) | misfit task load-balance tweaks 的补丁被拆分重构, 这个是 Part 1 | v3 ☐ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1409479) |
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| 2021/04/16 | Valentin Schneider | [sched/fair: (The return of) misfit task load-balance tweaks](https://lore.kernel.org/patchwork/cover/1414181) | misfit task load-balance tweaks 的补丁被拆分重构, 这个是 Part 2 | v1 ☐ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1414181) |
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| 2021/06/03 | Valentin Schneider | [Rework CPU capacity asymmetry detection](https://lore.kernel.org/patchwork/cover/1424708) | 当前版本 asym_cpu_capacity_level 存在几个问题.<br>1. 只能支持到最低的拓扑级别, 对全局的拓扑域不可见.<br>2. 不支持 NUMA 级别的异构, 因为初始化 NUMA 级别的 sd_numa_mask 中不包含其他 NODE, 最终 sched_domain_span 是在构建调度域的时候进行的更新的.<br>这对于大多数现有的不对称设计很实用, 但是却不支持普适的性能异构架构.这可能不是最好的方法, 在一些领域可能看不到任何不对称. 这对于不合适的迁移和能量感知的安置可能会有问题. 因此, 对于受影响的平台, 它可能导致对唤醒和 CPU 选择路径的自定义更改.<br>这组补丁修改了执行非对称检测的方式, 允许将非对称拓扑级别固定在最低的拓扑级别上, 在最低的拓扑级别上, 给定调度域中的所有 CPU 都可以看到整个 CPU 容量范围. asym_cpu_capacity_level 还将跟踪那些观察到任何非对称范围的级别, 以使用 SD_ASYM_CPUCAPACITY 标志表示相应的调度域, 并为这些域启用不匹配迁移. 为了区分局部和全范围 CPU 容量不对称的调度域, 引入了新的调度域标志: SD_ASYM_CPUCAPACITY_FULL. | v7 ☑ 5.14-rc1 | [PatchWork v1](https://lore.kernel.org/patchwork/cover/1414557)<br>*-*-*-*-*-*-*-* <br>[PatchWork v7](https://lore.kernel.org/all/20210603140627.8409-1-beata.michalska@arm.com) |
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异构拓扑优化
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* capacity aware wakeup
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| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
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|:----:|:----:|:---:|:---:|:----------:|:----:|
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| 2021/05/17 | Beata Michalska <beata.michalska@arm.com> | [Rework CPU capacity asymmetry detection](https://lore.kernel.org/patchwork/cover/1429483) | NA | v3 ☐ | [PatchWork v4](https://lore.kernel.org/patchwork/cover/1429483) |
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| 2020/02/06 | Vincent Guittot | [sched/fair: Capacity aware wakeup rework](https://lore.kernel.org/patchwork/cover/1190300) | 异构 CPU 上 wakeup 路径优化. 实现了 select_idle_capacity(), wakeup 进程时, 为进程选择 capacity 更合适的 CPU. | v4 ☑ 5.7-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1190300) |
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| 2020/12/19 | Vincent Guittot | [sched/fair: prefer prev cpu in asymmetric wakeup path](https://lore.kernel.org/patchwork/cover/1329119) | 异构 CPU 上 wakeup 路径倾向于使用 prev CPU | v1 ☑ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1308748) |
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* misfit task
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| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
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|:----:|:----:|:---:|:---:|:----------:|:----:|
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| 2018/03/15 | Morten Rasmussen | [sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems](https://lore.kernel.org/patchwork/cover/933989) | 实现 misfit, 可以理解为 asymmetric aware 的 load balance, 在进程运行过程中, 如果当前 CPU capacity 已经不能满足当前进程, 则将进程迁移到拥有更合适 capacity 的 CPU 上. | v1 ☑ 4.20-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/933989) |
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| 2021/03/11 | Valentin Schneider | [sched/fair: misfit task load-balance tweaks](https://lore.kernel.org/patchwork/cover/1393531) | 优化 misfit task 的一些逻辑 | v3 ☐ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1393531) |
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| 2021/04/07 | Valentin Schneider | [sched/fair: load-balance vs capacity margins](https://lore.kernel.org/patchwork/cover/1409479) | misfit task load-balance tweaks 的补丁被拆分重构, 这个是 Part 1 | v3 ☐ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1409479) |
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| 2021/04/16 | Valentin Schneider | [sched/fair: (The return of) misfit task load-balance tweaks](https://lore.kernel.org/patchwork/cover/1414181) | misfit task load-balance tweaks 的补丁被拆分重构, 这个是 Part 2 | v1 ☐ 5.10-rc4 | [PatchWork](https://lore.kernel.org/patchwork/cover/1414181) |
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* capacity aware sched class
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| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
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|:----:|:----:|:---:|:---:|:----------:|:----:|
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| 2020/05/20 | Dietmar Eggemann | [Capacity awareness for SCHED_DEADLINE](https://lore.kernel.org/patchwork/cover/1245028) | DEADLINE 感知 Capacity | v3 ☐ 5.9-rc1 | [PatchWork](https://lore.kernel.org/patchwork/cover/1245028) |
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* Document
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| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
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| 2020/07/31 | Valentin Schneider <valentin.schneider@arm.com> | [sched: Document capacity aware scheduling](https://lore.kernel.org/all/20200731192016.7484-1-valentin.schneider@arm.com) | 补充了 CAS(capacity aware scheduling) 的文档. | v1 ☑ 5.7-rc1 | [LORE 0/3](https://lore.kernel.org/all/20200731192016.7484-1-valentin.schneider@arm.com), [COMMIT](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=65065fd70b5a0f0bbe3f9f1e82c1d38c2db620d0) |
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## 7.3 基于调度器的调频
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