Updating Windows node eviction signals docs
Mark Rossett
Mark Rossetti
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45a47d170f
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b3ce13edaf
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@ -76,25 +76,27 @@ point in time. The kubelet uses eviction signals to make eviction decisions by
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comparing the signals to eviction thresholds, which are the minimum amount of
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the resource that should be available on the node.
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On Linux, the kubelet uses the following eviction signals:
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The kubelet uses the following eviction signals:
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| Eviction Signal | Description |
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|--------------------------|---------------------------------------------------------------------------------------|
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| `memory.available` | `memory.available` := `node.status.capacity[memory]` - `node.stats.memory.workingSet` |
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| `nodefs.available` | `nodefs.available` := `node.stats.fs.available` |
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| `nodefs.inodesFree` | `nodefs.inodesFree` := `node.stats.fs.inodesFree` |
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| `imagefs.available` | `imagefs.available` := `node.stats.runtime.imagefs.available` |
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| `imagefs.inodesFree` | `imagefs.inodesFree` := `node.stats.runtime.imagefs.inodesFree` |
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| `containerfs.available` | `containerfs.available` := `node.stats.runtime.containerfs.available` |
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| `containerfs.inodesFree` | `containerfs.inodesFree` := `node.stats.runtime.containerfs.inodesFree` |
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| `pid.available` | `pid.available` := `node.stats.rlimit.maxpid` - `node.stats.rlimit.curproc` |
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| Eviction Signal | Description | Linux Only |
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|--------------------------|---------------------------------------------------------------------------------------|------------|
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| `memory.available` | `memory.available` := `node.status.capacity[memory]` - `node.stats.memory.workingSet` | |
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| `nodefs.available` | `nodefs.available` := `node.stats.fs.available` | |
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| `nodefs.inodesFree` | `nodefs.inodesFree` := `node.stats.fs.inodesFree` | • |
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| `imagefs.available` | `imagefs.available` := `node.stats.runtime.imagefs.available` | |
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| `imagefs.inodesFree` | `imagefs.inodesFree` := `node.stats.runtime.imagefs.inodesFree` | • |
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| `containerfs.available` | `containerfs.available` := `node.stats.runtime.containerfs.available` | |
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| `containerfs.inodesFree` | `containerfs.inodesFree` := `node.stats.runtime.containerfs.inodesFree` | • |
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| `pid.available` | `pid.available` := `node.stats.rlimit.maxpid` - `node.stats.rlimit.curproc` | • |
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In this table, the **Description** column shows how kubelet gets the value of the
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signal. Each signal supports either a percentage or a literal value. The kubelet
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calculates the percentage value relative to the total capacity associated with
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the signal.
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The value for `memory.available` is derived from the cgroupfs instead of tools
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#### Memory signals
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On Linux nodes, the value for `memory.available` is derived from the cgroupfs instead of tools
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like `free -m`. This is important because `free -m` does not work in a
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container, and if users use the [node allocatable](/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable)
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feature, out of resource decisions
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@ -106,7 +108,14 @@ reproduces the same set of steps that the kubelet performs to calculate
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file-backed memory on the inactive LRU list) from its calculation, as it assumes that
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memory is reclaimable under pressure.
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The kubelet recognizes three specific filesystem identifiers:
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On Windows nodes, the value for `memory.available` is derived from the node's global
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memory commit levels (queried through the [`GetPerformanceInfo()`](https://learn.microsoft.com/windows/win32/api/psapi/nf-psapi-getperformanceinfo)
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system call) by subtracting the node's global [`CommitTotal`](https://learn.microsoft.com/windows/win32/api/psapi/ns-psapi-performance_information) from the node's [`CommitLimit`](https://learn.microsoft.com/windows/win32/api/psapi/ns-psapi-performance_information). Please note that `CommitLimit` can change if the node's page-file size changes!
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#### Filesystem signals
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The kubelet recognizes three specific filesystem identifiers that can be used with
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eviction signals (`<identifier>.inodesFree` or `<identifier>.available`):
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1. `nodefs`: The node's main filesystem, used for local disk volumes,
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emptyDir volumes not backed by memory, log storage, ephemeral storage,
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@ -144,6 +153,8 @@ other local node filesystems.
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The kubelet does not support other container filesystems or storage configurations,
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and it does not currently support multiple filesystems for images and containers.
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#### Deprecated kubelet garbage collection features
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Some kubelet garbage collection features are deprecated in favor of eviction:
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| Existing Flag | Rationale |
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@ -205,7 +216,8 @@ thresholds like `memory.available<1Gi`.
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The kubelet has the following default hard eviction thresholds:
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- `memory.available<100Mi`
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- `memory.available<100Mi` (Linux nodes)
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- `memory.available<500Mi` (Windows nodes)
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- `nodefs.available<10%`
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- `imagefs.available<15%`
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- `nodefs.inodesFree<5%` (Linux nodes)
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@ -149,13 +149,12 @@ Some kubelet command line options behave differently on Windows, as described be
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* The `--kube-reserved`, `--system-reserved` , and `--eviction-hard` flags update
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[NodeAllocatable](/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable)
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* Eviction by using `--enforce-node-allocable` is not implemented
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* Eviction by using `--eviction-hard` and `--eviction-soft` are not implemented
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* When running on a Windows node the kubelet does not have memory or CPU
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restrictions. `--kube-reserved` and `--system-reserved` only subtract from `NodeAllocatable`
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and do not guarantee resource provided for workloads.
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See [Resource Management for Windows nodes](/docs/concepts/configuration/windows-resource-management/#resource-reservation)
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for more information.
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* The `MemoryPressure` Condition is not implemented
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* The `PIDPressure` Condition is not implemented
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* The kubelet does not take OOM eviction actions
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### API compatibility {#api}
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