website/content/en/docs/concepts/scheduling-eviction/resource-bin-packing.md

---
reviewers:
- bsalamat
- k82cn
- ahg-g
title: Resource Bin Packing for Extended Resources
content_type: concept
weight: 80
---

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{{< feature-state for_k8s_version="v1.16" state="alpha" >}}

The kube-scheduler can be configured to enable bin packing of resources along
with extended resources using `RequestedToCapacityRatioResourceAllocation`
priority function. Priority functions can be used to fine-tune the
kube-scheduler as per custom needs. 

<!-- body -->

## Enabling Bin Packing using RequestedToCapacityRatioResourceAllocation

Kubernetes allows the users to specify the resources along with weights for
each resource to score nodes based on the request to capacity ratio. This
allows users to bin pack extended resources by using appropriate parameters
and improves the utilization of scarce resources in large clusters. The
behavior of the `RequestedToCapacityRatioResourceAllocation` priority function
can be controlled by a configuration option called `RequestedToCapacityRatioArgs`. 
This argument consists of two parameters `shape` and `resources`. The `shape` 
parameter allows the user to tune the function as least requested or most 
requested based on `utilization` and `score` values.  The `resources` parameter 
consists of `name` of the resource to be considered during scoring and `weight` 
specify the weight of each resource.

Below is an example configuration that sets
`requestedToCapacityRatioArguments` to bin packing behavior for extended
resources `intel.com/foo` and `intel.com/bar`.

```yaml
apiVersion: kubescheduler.config.k8s.io/v1beta3
kind: KubeSchedulerConfiguration
profiles:
# ...
  pluginConfig:
  - name: RequestedToCapacityRatio
    args: 
      shape:
      - utilization: 0
        score: 10
      - utilization: 100
        score: 0
      resources:
      - name: intel.com/foo
        weight: 3
      - name: intel.com/bar
        weight: 5
```

Referencing the `KubeSchedulerConfiguration` file with the kube-scheduler 
flag `--config=/path/to/config/file` will pass the configuration to the 
scheduler.

**This feature is disabled by default**

### Tuning the Priority Function

`shape` is used to specify the behavior of the
`RequestedToCapacityRatioPriority` function.

```yaml
shape:
 - utilization: 0
   score: 0
 - utilization: 100
   score: 10
```

The above arguments give the node a `score` of 0 if `utilization` is 0% and 10 for
`utilization` 100%, thus enabling bin packing behavior. To enable least
requested the score value must be reversed as follows.

```yaml
shape:
  - utilization: 0
    score: 10
  - utilization: 100
    score: 0
```

`resources` is an optional parameter which defaults to:

``` yaml
resources:
  - name: cpu
    weight: 1
  - name: memory
    weight: 1
```

It can be used to add extended resources as follows: 

```yaml
resources:
  - name: intel.com/foo
    weight: 5
  - name: cpu
    weight: 3
  - name: memory
    weight: 1
```

The `weight` parameter is optional and is set to 1 if not specified. Also, the
`weight` cannot be set to a negative value.

### Node scoring for capacity allocation

This section is intended for those who want to understand the internal details
of this feature.
Below is an example of how the node score is calculated for a given set of values.

Requested resources:

```
intel.com/foo : 2
memory: 256MB
cpu: 2
```

Resource weights:

```
intel.com/foo : 5
memory: 1
cpu: 3
```

FunctionShapePoint {{0, 0}, {100, 10}}

Node 1 spec:

```
Available:
  intel.com/foo: 4
  memory: 1 GB
  cpu: 8

Used:
  intel.com/foo: 1
  memory: 256MB
  cpu: 1
```

Node score:

```
intel.com/foo  = resourceScoringFunction((2+1),4)
               = (100 - ((4-3)*100/4)
               = (100 - 25)
               = 75                       # requested + used = 75% * available
               = rawScoringFunction(75) 
               = 7                        # floor(75/10) 

memory         = resourceScoringFunction((256+256),1024)
               = (100 -((1024-512)*100/1024))
               = 50                       # requested + used = 50% * available
               = rawScoringFunction(50)
               = 5                        # floor(50/10)

cpu            = resourceScoringFunction((2+1),8)
               = (100 -((8-3)*100/8))
               = 37.5                     # requested + used = 37.5% * available
               = rawScoringFunction(37.5)
               = 3                        # floor(37.5/10)

NodeScore   =  (7 * 5) + (5 * 1) + (3 * 3) / (5 + 1 + 3)
            =  5
```

Node 2 spec:

```
Available:
  intel.com/foo: 8
  memory: 1GB
  cpu: 8
Used:
  intel.com/foo: 2
  memory: 512MB
  cpu: 6
```

Node score:

```
intel.com/foo  = resourceScoringFunction((2+2),8)
               =  (100 - ((8-4)*100/8)
               =  (100 - 50)
               =  50
               =  rawScoringFunction(50)
               = 5

memory         = resourceScoringFunction((256+512),1024)
               = (100 -((1024-768)*100/1024))
               = 75
               = rawScoringFunction(75)
               = 7

cpu            = resourceScoringFunction((2+6),8)
               = (100 -((8-8)*100/8))
               = 100
               = rawScoringFunction(100)
               = 10

NodeScore   =  (5 * 5) + (7 * 1) + (10 * 3) / (5 + 1 + 3)
            =  7

```

## {{% heading "whatsnext" %}}

- Read more about the [scheduling framework](/docs/concepts/scheduling-eviction/scheduling-framework/)
- Read more about [scheduler configuration](/docs/reference/scheduling/config/)