[FLINK-33392][docs] Add the documentation pages for balanced tasks scheduling.

docs/content.zh/docs/deployment/tasks-scheduling/_index.md

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+---
+title: Tasks Scheduling
+bookCollapseSection: true
+weight: 9
+---
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->

docs/content.zh/docs/deployment/tasks-scheduling/balanced_tasks_scheduling.md

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+---
+title: Balanced Tasks Scheduling
+weight: 5
+type: docs
+
+---
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# Balanced Tasks Scheduling
+
+This page describes the background and principle of balanced tasks scheduling, 
+how to use it when running streaming jobs.
+
+## Background
+
+When the parallelism of all vertices within a Flink streaming job is inconsistent,
+the [default strategy]({{< ref "docs/deployment/config" >}}#taskmanager-load-balance-mode)
+of Flink to deploy tasks sometimes leads some `TaskManagers` have more tasks while others have fewer tasks, 
+resulting in excessive resource utilization at some `TaskManagers` 
+that contain more tasks and becoming a bottleneck for the entire job processing.
+
+{{< img src="/fig/deployments/tasks-scheduling/tasks_scheduling_skew_case.svg" alt="The Skew Case of Tasks Scheduling" class="offset" width="50%" >}}
+
+As shown in figure (a), given a Flink job comprising two vertices, `JobVertex-A (JV-A)` and `JobVertex-B (JV-B)`, 
+with parallelism degrees of `6` and `3` respectively,
+and both vertices sharing the same slot sharing group.
+Under the default tasks scheduling strategy, as illustrated in figure (b), 
+the distribution of tasks across `TaskManagers` may result in significant disparities in task load. 
+Specifically, the `TaskManager`s with the highest number of tasks may host `4` tasks, 
+while the one with the lowest load may have only `2` tasks. 
+Consequently, the `TaskManager`s bearing 4 tasks is prone to become a performance bottleneck for the entire job.
+
+Therefore, Flink provides a task-quantity-based balanced tasks scheduling capability. 
+Within the job's resource view, it aims to ensure that the number of tasks 
+scheduled to each `TaskManager` as close as possible to, thereby improving the resource usage skew among `TaskManagers`.
+
+## Principle
+
+The task-quantity-based load balancing tasks scheduling strategy completes the assignment of tasks to `TaskManagers` in two phases: 
+- The tasks-to-slots assignment phase 
+- The slots-to-TaskManagers assignment phase
+
+This section will use two examples to illustrate the simplified process and principle of 
+how the task-quantity-based tasks scheduling strategy handles the assignments in these two phases.
+
+### The tasks-to-slots assignment phase
+
+Taking the job shown in figure (c) as an example, it contains five job vertices with parallelism degrees of `1`, `4`, `4`, `2`, and `3`, respectively.
+All five job vertices belong to the default slot sharing group.  
+
+{{< img src="/fig/deployments/tasks-scheduling/tasks_to_slots_allocation_principle.svg" alt="The Tasks To Slots Allocation Principle Demo" class="offset" width="65%" >}}
+
+During the tasks-to-slots assignment phase, this tasks scheduling strategy:  
+- First directly assigns the tasks of the vertices with the highest parallelism to the `i-th` slot. 
+
+  That is, task `JV-Bi` is assigned directly to `sloti`, and task `JV-Ci` is assigned directly to `sloti`.
+
+- Next, for tasks belonging to job vertices with sub-maximal parallelism, they are assigned in a round-robin fashion across the slots within the current
+slot sharing group until all tasks are allocated.
+
+As shown in figure (e), under the task-quantity-based assignment strategy, the range (max-min difference) of the number of tasks per slot is `1`, 
+which is better than the range of `3` under the default strategy shown in figure (d).
+
+Thus, this ensures a more balanced distribution of the number of tasks across slots.
+
+### The slots-to-TaskManagers assignment phase
+
+As shown in figure (f), given a Flink job comprising two vertices, `JV-A` and `JV-B`, with parallelism of `6` and `3` respectively,
+and both vertices sharing the same slot sharing group.
+
+{{< img src="/fig/deployments/tasks-scheduling/slots_to_taskmanagers_allocation_principle.svg" alt="The Slots to TaskManagers Allocation Principle Demo" class="offset" width="75%" >}}
+
+The assignment result after the first phase is shown in figure (g), 
+where `Slot0`, `Slot1`, and `Slot2` each contain `2` tasks, while the remaining slots contain `1` task each.
+
+Subsequently:
+- The strategy submits all slot requests and waits until all slot resources required for the current job are ready.
+
+Once the slot resources are ready:  
+- The strategy then sorts all slot requests in descending order based on the number of tasks contained in each request. 
+Afterwards, it sequentially assigns each slot request to the `TaskManager` with the smallest current tasks loading. 
+This process continues until all slot requests have been allocated.
+
+The final assignment result is shown in figure (i), where each `TaskManager` ends up with exactly `3` tasks, 
+resulting in a task count difference of `0` between `TaskManagers`. In contrast, the scheduling result under the default strategy, 
+shown in figure (h), has a task count difference of `2` between `TaskManagers`. 
+
+Therefore, theoretically, using this load balancing tasks scheduling strategy could effectively mitigate the issue of 
+resource usage skew caused by significant disparities in the number of tasks across `TaskManagers` .
+
+## Usage
+
+You can enable balanced tasks scheduling through the following configuration item: 
+
+- `taskmanager.load-balance.mode`: `tasks`
+
+## More details
+
+See the <a href="https://cwiki.apache.org/confluence/x/U56zDw">FLIP-370</a> for more details.
+
+{{< top >}}

docs/content/docs/deployment/tasks-scheduling/_index.md

@@ -0,0 +1,23 @@
+---
+title: Tasks Scheduling
+bookCollapseSection: true
+weight: 9
+---
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->

docs/content/docs/deployment/tasks-scheduling/balanced_tasks_scheduling.md

@@ -0,0 +1,118 @@
+---
+title: Balanced Tasks Scheduling
+weight: 5
+type: docs
+
+---
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# Balanced Tasks Scheduling
+
+This page describes the background and principle of balanced tasks scheduling, 
+how to use it when running streaming jobs.
+
+## Background
+
+When the parallelism of all vertices within a Flink streaming job is inconsistent,
+the [default strategy]({{< ref "docs/deployment/config" >}}#taskmanager-load-balance-mode)
+of Flink to deploy tasks sometimes leads some `TaskManagers` have more tasks while others have fewer tasks, 
+resulting in excessive resource utilization at some `TaskManagers` 
+that contain more tasks and becoming a bottleneck for the entire job processing.
+
+{{< img src="/fig/deployments/tasks-scheduling/tasks_scheduling_skew_case.svg" alt="The Skew Case of Tasks Scheduling" class="offset" width="50%" >}}
+
+As shown in figure (a), given a Flink job comprising two vertices, `JobVertex-A (JV-A)` and `JobVertex-B (JV-B)`, 
+with parallelism degrees of `6` and `3` respectively,
+and both vertices sharing the same slot sharing group.
+Under the default tasks scheduling strategy, as illustrated in figure (b), 
+the distribution of tasks across `TaskManagers` may result in significant disparities in task load. 
+Specifically, the `TaskManager`s with the highest number of tasks may host `4` tasks, 
+while the one with the lowest load may have only `2` tasks. 
+Consequently, the `TaskManager`s bearing 4 tasks is prone to become a performance bottleneck for the entire job.
+
+Therefore, Flink provides a task-quantity-based balanced tasks scheduling capability. 
+Within the job's resource view, it aims to ensure that the number of tasks 
+scheduled to each `TaskManager` as close as possible to, thereby improving the resource usage skew among `TaskManagers`.
+
+## Principle
+
+The task-quantity-based load balancing tasks scheduling strategy completes the assignment of tasks to `TaskManagers` in two phases: 
+- The tasks-to-slots assignment phase 
+- The slots-to-TaskManagers assignment phase
+
+This section will use two examples to illustrate the simplified process and principle of 
+how the task-quantity-based tasks scheduling strategy handles the assignments in these two phases.
+
+### The tasks-to-slots assignment phase
+
+Taking the job shown in figure (c) as an example, it contains five job vertices with parallelism degrees of `1`, `4`, `4`, `2`, and `3`, respectively.
+All five job vertices belong to the default slot sharing group.  
+
+{{< img src="/fig/deployments/tasks-scheduling/tasks_to_slots_allocation_principle.svg" alt="The Tasks To Slots Allocation Principle Demo" class="offset" width="65%" >}}
+
+During the tasks-to-slots assignment phase, this tasks scheduling strategy:  
+- First directly assigns the tasks of the vertices with the highest parallelism to the `i-th` slot. 
+
+  That is, task `JV-Bi` is assigned directly to `sloti`, and task `JV-Ci` is assigned directly to `sloti`.
+
+- Next, for tasks belonging to job vertices with sub-maximal parallelism, they are assigned in a round-robin fashion across the slots within the current
+slot sharing group until all tasks are allocated.
+
+As shown in figure (e), under the task-quantity-based assignment strategy, the range (max-min difference) of the number of tasks per slot is `1`, 
+which is better than the range of `3` under the default strategy shown in figure (d).
+
+Thus, this ensures a more balanced distribution of the number of tasks across slots.
+
+### The slots-to-TaskManagers assignment phase
+
+As shown in figure (f), given a Flink job comprising two vertices, `JV-A` and `JV-B`, with parallelism of `6` and `3` respectively,
+and both vertices sharing the same slot sharing group.
+
+{{< img src="/fig/deployments/tasks-scheduling/slots_to_taskmanagers_allocation_principle.svg" alt="The Slots to TaskManagers Allocation Principle Demo" class="offset" width="75%" >}}
+
+The assignment result after the first phase is shown in figure (g), 
+where `Slot0`, `Slot1`, and `Slot2` each contain `2` tasks, while the remaining slots contain `1` task each.
+
+Subsequently:
+- The strategy submits all slot requests and waits until all slot resources required for the current job are ready.
+
+Once the slot resources are ready:  
+- The strategy then sorts all slot requests in descending order based on the number of tasks contained in each request. 
+Afterwards, it sequentially assigns each slot request to the `TaskManager` with the smallest current tasks loading. 
+This process continues until all slot requests have been allocated.
+
+The final assignment result is shown in figure (i), where each `TaskManager` ends up with exactly `3` tasks, 
+resulting in a task count difference of `0` between `TaskManagers`. In contrast, the scheduling result under the default strategy, 
+shown in figure (h), has a task count difference of `2` between `TaskManagers`. 
+
+Therefore, theoretically, using this load balancing tasks scheduling strategy could effectively mitigate the issue of 
+resource usage skew caused by significant disparities in the number of tasks across `TaskManagers` .
+
+## Usage
+
+You can enable balanced tasks scheduling through the following configuration item: 
+
+- `taskmanager.load-balance.mode`: `tasks`
+
+## More details
+
+See the <a href="https://cwiki.apache.org/confluence/x/U56zDw">FLIP-370</a> for more details.
+
+{{< top >}}