docs: overcommit-plugin enhancements

[googs1025]

Fix: #3635

overcommit-plugin

@googs1025; Jul. 29, 2024

Background:

The overcommit-plugin is used to amplify node resources to achieve resource allocation.

Objective:

Use different amplification factors based on different resource types.

Introduction

Currently, the overcommit-plugin enhances the Allocatable resources of a node to achieve the functionality of AddJobEnqueuedFn. However, different resources should have different factors, so using the same overcommit-factor is not appropriate.

• For example:

The Binpack plugin assigns different weights to different resources as well.

actions: "enqueue, reclaim, allocate, backfill, preempt"
tiers:
- plugins:
  - name: binpack
    arguments:
      binpack.weight: 10
      binpack.cpu: 5
      binpack.memory: 1
      binpack.resources: nvidia.com/gpu, example.com/foo
      binpack.resources.nvidia.com/gpu: 2
      binpack.resources.example.com/foo: 3

Solution

We can further break down the overcommit-factor into more granular components: overcommit-factor.<resource name>.

For example: overcommit-factor.cpu overcommit-factor.memory overcommit-factor.pods overcommit-factor.ephemeral-storage overcommit-factor.nvidia.com/gpu

To maintain compatibility with the existing approach, we will retain the original overcommit-factor field and we will keep the original overcommit-factor field and introduce an optional field of overcommit-factor.<resource name>.

The priority of these fields will be from low to high:

defaultOverCommitFactor -> overcommit-factor -> overcommit-factor.<resorce name>

• overcommitPlugin struct

// overcommitFactors defines the resource overCommit factors
type overcommitFactors struct {
	// factorMaps defines the resource overCommit factors
    // key: resource, example: "cpu", "memory", "ephemeral-storage", "nvidia.com/gpu"
    // value: overCommit factors
    factorMaps map[string]float64
}

type overcommitPlugin struct {
    // Arguments given for the plugin
    pluginArguments  framework.Arguments
    totalResource    *api.Resource
    idleResource     *api.Resource
    inqueueResource  *api.Resource
    // overCommitFactor is the different resource overCommit factors
    overCommitFactors *overcommitFactors
}

Example

Example 1:
Explicitly specify all the overcommit factors

actions: "enqueue, allocate, backfill"
tiers:
- plugins:
  - name: overcommit
    arguments:
    overcommit-factor.cpu: 1.2
    overcommit-factor.memory: 1.0
    overcommit-factor.ephemeral-storage: 1.2
    overcommit-factor.pods: 1.2
    overcommit-factor.nvidia.com/gpu: 1.2

Example 2:
Specifying only the overcommit-factor implies that all factors are the same.

actions: "enqueue, allocate, backfill"
tiers:
- plugins:
  - name: overcommit
    arguments:
    overcommit-factor: 1.3

Example 3:
Specifying overcommit-factor.cpu, overcommit-factor.nvidia.com/gpu are set, along with specifying overcommit-factor: indicates that the resource uses a specific value, while other values use the overcommit-factor field.

actions: "enqueue, allocate, backfill"
tiers:
- plugins:
  - name: overcommit
    arguments:
    overcommit-factor.cpu: 1.2
    overcommit-factor.nvidia.com/gpu: 1.3
    overcommit-factor: 1.0

Example 4:
Specifying any one of overcommit-factor.cpu is set: indicates that the resource uses a specific value, while other values use the defaultOverCommitFactor default value.

actions: "enqueue, allocate, backfill"
tiers:
- plugins:
  - name: overcommit
    arguments:
    overcommit-factor.cpu: 1.2

Example 5:
Not specifying will default to the defaultOverCommitFactor value.

actions: "enqueue, allocate, backfill"
tiers:
- plugins:
  - name: overcommit
    arguments:

[hwdef]

Why not put it in the overcommit document, but create a new document?

[googs1025]

Why not put it in the overcommit document, but create a new document?

I would like to, but I can't seem to find any design documentation related to overcommit plugins

[hwdef]

You can name your document overcommit-plugin.md

[googs1025]

enhancements

I can modify it. I named it overcommit-plugin-enhancements because overcommit-plugin itself was not designed by me and I may not be sure of many backgrounds.

[googs1025]

/kind docs
/kind feature

[hwdef]

enhancements

I can modify it. I named it overcommit-plugin-enhancements because overcommit-plugin itself was not designed by me and I may not be sure of many backgrounds.

Never mind, overcommit plugin is simple, and I believe you can understand it completely. This is also a supplement to the missing documentation in the community.

[googs1025]

enhancements

I can modify it. I named it overcommit-plugin-enhancements because overcommit-plugin itself was not designed by me and I may not be sure of many backgrounds.

Never mind, overcommit plugin is simple, and I believe you can understand it completely. This is also a supplement to the missing documentation in the community.

thanks! done

[googs1025]

If having time, please take a look at this issue. @lowang-bh @Monokaix thanks a lot

[lowang-bh]

In which scene, other resource will have a overcommit request ？ Does gpu support overcommit？

[googs1025]

In my understanding, GPU resources should not be over-resolved. (Please correct me if I am wrong.) Originally, this plugin multiplied all resources by a fixed overcommit factor. This proposal is to enhance this. We should not make all configurations consistent. The overcommit factor should be configured more flexibly.

[googs1025]

This effectively separates incompressible resources from compressible resources and sets them differently.

[googs1025]

The overcommit plugin is activated when a job is enqueued, and it allows more jobs to enter the Inqueue state by amplifying the factor.

[lowang-bh]

Please refer to predicate.Proportional function in predicate plugin.

[volcano-sh-bot]

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