# Semantic conventions for system metrics **Status**: [Development][DocumentStatus] This document describes instruments and attributes for common system level metrics in OpenTelemetry. Consider the [general metric semantic conventions](/docs/specs/semconv/general/metrics.md#general-guidelines) when creating instruments not explicitly defined in the specification. The `system.*` namespace SHOULD be exclusively used to report hosts' metrics. The `system.*` namespace SHOULD only be used when the metrics are collected from within the target system. (physical servers, virtual machines etc). Metrics collected from technology-specific, well-defined APIs (e.g. Kubelet's API or container runtimes) should be reported under their respective namespace (e.g. `k8s.*`, `container.*`). Resource attributes related to a host, SHOULD be reported under the `host.*` namespace. > [!IMPORTANT] > Existing instrumentations and collector that are using > [v1.21.0 of this document](https://github.com/open-telemetry/semantic-conventions/blob/v1.21.0/docs/system/system-metrics.md) > (or prior): > > * SHOULD NOT adopt any breaking changes from document until the system > semantic conventions are marked stable. Conventions include, but are not > limited to, attributes, metric names, and unit of measure. > * SHOULD introduce a control mechanism to allow users to opt-in to the new > conventions once the migration plan is finalized. ## General metrics ### Metric: `system.uptime` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.uptime` | Gauge | `s` | The time the system has been running. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** Instrumentations SHOULD use a gauge with type `double` and measure uptime in seconds as a floating point number with the highest precision available. The actual accuracy would depend on the instrumentation and operating system. ## Processor metrics **Description:** System level processor metrics captured under the namespace `system.cpu`. ### Metric: `system.cpu.physical.count` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.cpu.physical.count` | UpDownCounter | `{cpu}` | Reports the number of actual physical processor cores on the hardware. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** Calculated by multiplying the number of sockets by the number of cores per socket ### Metric: `system.cpu.logical.count` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.cpu.logical.count` | UpDownCounter | `{cpu}` | Reports the number of logical (virtual) processor cores created by the operating system to manage multitasking. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** Calculated by multiplying the number of sockets by the number of cores per socket, and then by the number of threads per core ### Metric: `system.cpu.time` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.cpu.time` | Counter | `s` | Seconds each logical CPU spent on each mode. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`cpu.mode`](/docs/specs/semconv/registry/attributes/cpu.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The mode of the CPU [1] | `user`; `system` | | [`cpu.logical_number`](/docs/specs/semconv/registry/attributes/cpu.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Opt-In` | int | The logical CPU number [0..n-1] | `1` | **[1] `cpu.mode`:** Following states SHOULD be used: `user`, `system`, `nice`, `idle`, `iowait`, `interrupt`, `steal` --- `cpu.mode` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `idle` | Idle | ![Development](https://img.shields.io/badge/-development-blue) | | `interrupt` | Interrupt | ![Development](https://img.shields.io/badge/-development-blue) | | `iowait` | IO Wait | ![Development](https://img.shields.io/badge/-development-blue) | | `kernel` | Kernel | ![Development](https://img.shields.io/badge/-development-blue) | | `nice` | Nice | ![Development](https://img.shields.io/badge/-development-blue) | | `steal` | Steal | ![Development](https://img.shields.io/badge/-development-blue) | | `system` | System | ![Development](https://img.shields.io/badge/-development-blue) | | `user` | User | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.cpu.frequency` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.cpu.frequency` | Gauge | `Hz` | Operating frequency of the logical CPU in Hertz. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`cpu.logical_number`](/docs/specs/semconv/registry/attributes/cpu.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | int | The logical CPU number [0..n-1] | `1` | ### Metric: `system.cpu.utilization` This metric is [opt-in][MetricOptIn]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.cpu.utilization` | Gauge | `1` | For each logical CPU, the utilization is calculated as the change in cumulative CPU time (cpu.time) over a measurement interval, divided by the elapsed time. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`cpu.mode`](/docs/specs/semconv/registry/attributes/cpu.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The mode of the CPU [1] | `user`; `system` | | [`cpu.logical_number`](/docs/specs/semconv/registry/attributes/cpu.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Opt-In` | int | The logical CPU number [0..n-1] | `1` | **[1] `cpu.mode`:** Following modes SHOULD be used: `user`, `system`, `nice`, `idle`, `iowait`, `interrupt`, `steal` --- `cpu.mode` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `idle` | Idle | ![Development](https://img.shields.io/badge/-development-blue) | | `interrupt` | Interrupt | ![Development](https://img.shields.io/badge/-development-blue) | | `iowait` | IO Wait | ![Development](https://img.shields.io/badge/-development-blue) | | `kernel` | Kernel | ![Development](https://img.shields.io/badge/-development-blue) | | `nice` | Nice | ![Development](https://img.shields.io/badge/-development-blue) | | `steal` | Steal | ![Development](https://img.shields.io/badge/-development-blue) | | `system` | System | ![Development](https://img.shields.io/badge/-development-blue) | | `user` | User | ![Development](https://img.shields.io/badge/-development-blue) | ## Memory metrics **Description:** System level memory metrics capture under the namespace `system.memory`. This does not include [paging/swap memory](#pagingswap-metrics). ### Metric: `system.memory.usage` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.memory.usage` | UpDownCounter | `By` | Reports memory in use by state. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.memory.state`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The memory state | `free`; `cached` | --- `system.memory.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `buffers` | buffers | ![Development](https://img.shields.io/badge/-development-blue) | | `cached` | cached | ![Development](https://img.shields.io/badge/-development-blue) | | `free` | free | ![Development](https://img.shields.io/badge/-development-blue) | | `used` | Actual used virtual memory in bytes. [1] | ![Development](https://img.shields.io/badge/-development-blue) | **[1]:** Calculation based on the operating system metrics. On Linux, this corresponds to "MemTotal - MemAvailable" from /proc/meminfo, which more accurately reflects memory in active use by applications compared to older formulas based on free, cached, and buffers. If MemAvailable is not available, a fallback to those older formulas may be used. ### Metric: `system.memory.limit` This metric is [opt-in][MetricOptIn]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.memory.limit` | UpDownCounter | `By` | Total virtual memory available in the system. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | ### Metric: `system.memory.utilization` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.memory.utilization` | Gauge | `1` | Percentage of memory bytes in use. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.memory.state`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The memory state | `free`; `cached` | --- `system.memory.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `buffers` | buffers | ![Development](https://img.shields.io/badge/-development-blue) | | `cached` | cached | ![Development](https://img.shields.io/badge/-development-blue) | | `free` | free | ![Development](https://img.shields.io/badge/-development-blue) | | `used` | Actual used virtual memory in bytes. [1] | ![Development](https://img.shields.io/badge/-development-blue) | **[1]:** Calculation based on the operating system metrics. On Linux, this corresponds to "MemTotal - MemAvailable" from /proc/meminfo, which more accurately reflects memory in active use by applications compared to older formulas based on free, cached, and buffers. If MemAvailable is not available, a fallback to those older formulas may be used. ## Paging/Swap Metrics **Description:** System level paging/swap memory metrics captured under the namespace `system.paging`. ### Metric: `system.paging.usage` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.paging.usage` | UpDownCounter | `By` | Unix swap or windows pagefile usage. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | Unique identifier for the device responsible for managing paging operations. | `/dev/dm-0` | | [`system.paging.state`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The memory paging state | `free` | --- `system.paging.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `free` | free | ![Development](https://img.shields.io/badge/-development-blue) | | `used` | used | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.paging.utilization` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.paging.utilization` | Gauge | `1` | Swap (unix) or pagefile (windows) utilization. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | Unique identifier for the device responsible for managing paging operations. | `/dev/dm-0` | | [`system.paging.state`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The memory paging state | `free` | --- `system.paging.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `free` | free | ![Development](https://img.shields.io/badge/-development-blue) | | `used` | used | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.paging.faults` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.paging.faults` | Counter | `{fault}` | The number of page faults. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.paging.fault.type`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The paging fault type | `minor` | --- `system.paging.fault.type` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `major` | major | ![Development](https://img.shields.io/badge/-development-blue) | | `minor` | minor | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.paging.operations` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.paging.operations` | Counter | `{operation}` | The number of paging operations. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.paging.direction`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The paging access direction | `in` | | [`system.paging.fault.type`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The paging fault type | `minor` | --- `system.paging.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `in` | in | ![Development](https://img.shields.io/badge/-development-blue) | | `out` | out | ![Development](https://img.shields.io/badge/-development-blue) | --- `system.paging.fault.type` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `major` | major | ![Development](https://img.shields.io/badge/-development-blue) | | `minor` | minor | ![Development](https://img.shields.io/badge/-development-blue) | ## Disk controller metrics **Description:** System level disk performance metrics captured under the namespace `system.disk`. ### Metric: `system.disk.io` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.disk.io` | Counter | `By` | Disk bytes transferred. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`disk.io.direction`](/docs/specs/semconv/registry/attributes/disk.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The disk IO operation direction. | `read` | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The device identifier | `(identifier)` | --- `disk.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `read` | read | ![Development](https://img.shields.io/badge/-development-blue) | | `write` | write | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.disk.operations` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.disk.operations` | Counter | `{operation}` | Disk operations count. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`disk.io.direction`](/docs/specs/semconv/registry/attributes/disk.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The disk IO operation direction. | `read` | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The device identifier | `(identifier)` | --- `disk.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `read` | read | ![Development](https://img.shields.io/badge/-development-blue) | | `write` | write | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.disk.io_time` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.disk.io_time` | Counter | `s` | Time disk spent activated. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** The real elapsed time ("wall clock") used in the I/O path (time from operations running in parallel are not counted). Measured as: - Linux: Field 13 from [procfs-diskstats](https://www.kernel.org/doc/Documentation/ABI/testing/procfs-diskstats) - Windows: The complement of ["Disk\% Idle Time"](https://learn.microsoft.com/archive/blogs/askcore/windows-performance-monitor-disk-counters-explained#windows-performance-monitor-disk-counters-explained) performance counter: `uptime * (100 - "Disk\% Idle Time") / 100` **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The device identifier | `(identifier)` | ### Metric: `system.disk.operation_time` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.disk.operation_time` | Counter | `s` | Sum of the time each operation took to complete. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** Because it is the sum of time each request took, parallel-issued requests each contribute to make the count grow. Measured as: - Linux: Fields 7 & 11 from [procfs-diskstats](https://www.kernel.org/doc/Documentation/ABI/testing/procfs-diskstats) - Windows: "Avg. Disk sec/Read" perf counter multiplied by "Disk Reads/sec" perf counter (similar for Writes) **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`disk.io.direction`](/docs/specs/semconv/registry/attributes/disk.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The disk IO operation direction. | `read` | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The device identifier | `(identifier)` | --- `disk.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `read` | read | ![Development](https://img.shields.io/badge/-development-blue) | | `write` | write | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.disk.merged` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.disk.merged` | Counter | `{operation}` | The number of disk reads/writes merged into single physical disk access operations. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`disk.io.direction`](/docs/specs/semconv/registry/attributes/disk.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The disk IO operation direction. | `read` | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The device identifier | `(identifier)` | --- `disk.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `read` | read | ![Development](https://img.shields.io/badge/-development-blue) | | `write` | write | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.disk.limit` This metric is [opt-in][MetricOptIn]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.disk.limit` | UpDownCounter | `By` | The total storage capacity of the disk. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The device identifier | `(identifier)` | ## Filesystem metrics **Description:** System level filesystem metrics captured under the namespace `system.filesystem`. ### Metric: `system.filesystem.usage` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.filesystem.usage` | UpDownCounter | `By` | Reports a filesystem's space usage across different states. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** The sum of all `system.filesystem.usage` values over the different `system.filesystem.state` attributes SHOULD equal the total storage capacity of the filesystem, that is `system.filesystem.limit`. **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | Identifier for the device where the filesystem resides. | `/dev/sda`; `\network-drive` | | [`system.filesystem.mode`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem mode | `rw, ro` | | [`system.filesystem.mountpoint`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem mount path | `/mnt/data` | | [`system.filesystem.state`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem state | `used` | | [`system.filesystem.type`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem type | `ext4` | --- `system.filesystem.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `free` | free | ![Development](https://img.shields.io/badge/-development-blue) | | `reserved` | reserved | ![Development](https://img.shields.io/badge/-development-blue) | | `used` | used | ![Development](https://img.shields.io/badge/-development-blue) | --- `system.filesystem.type` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `exfat` | exfat | ![Development](https://img.shields.io/badge/-development-blue) | | `ext4` | ext4 | ![Development](https://img.shields.io/badge/-development-blue) | | `fat32` | fat32 | ![Development](https://img.shields.io/badge/-development-blue) | | `hfsplus` | hfsplus | ![Development](https://img.shields.io/badge/-development-blue) | | `ntfs` | ntfs | ![Development](https://img.shields.io/badge/-development-blue) | | `refs` | refs | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.filesystem.utilization` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.filesystem.utilization` | Gauge | `1` | Fraction of filesystem bytes used. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | Identifier for the device where the filesystem resides. | `/dev/sda`; `\network-drive` | | [`system.filesystem.mode`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem mode | `rw, ro` | | [`system.filesystem.mountpoint`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem mount path | `/mnt/data` | | [`system.filesystem.state`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem state | `used` | | [`system.filesystem.type`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem type | `ext4` | --- `system.filesystem.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `free` | free | ![Development](https://img.shields.io/badge/-development-blue) | | `reserved` | reserved | ![Development](https://img.shields.io/badge/-development-blue) | | `used` | used | ![Development](https://img.shields.io/badge/-development-blue) | --- `system.filesystem.type` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `exfat` | exfat | ![Development](https://img.shields.io/badge/-development-blue) | | `ext4` | ext4 | ![Development](https://img.shields.io/badge/-development-blue) | | `fat32` | fat32 | ![Development](https://img.shields.io/badge/-development-blue) | | `hfsplus` | hfsplus | ![Development](https://img.shields.io/badge/-development-blue) | | `ntfs` | ntfs | ![Development](https://img.shields.io/badge/-development-blue) | | `refs` | refs | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.filesystem.limit` This metric is [opt-in][MetricOptIn]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.filesystem.limit` | UpDownCounter | `By` | The total storage capacity of the filesystem. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | Identifier for the device where the filesystem resides. | `/dev/sda`; `\network-drive` | | [`system.filesystem.mode`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem mode | `rw, ro` | | [`system.filesystem.mountpoint`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem mount path | `/mnt/data` | | [`system.filesystem.type`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The filesystem type | `ext4` | --- `system.filesystem.type` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `exfat` | exfat | ![Development](https://img.shields.io/badge/-development-blue) | | `ext4` | ext4 | ![Development](https://img.shields.io/badge/-development-blue) | | `fat32` | fat32 | ![Development](https://img.shields.io/badge/-development-blue) | | `hfsplus` | hfsplus | ![Development](https://img.shields.io/badge/-development-blue) | | `ntfs` | ntfs | ![Development](https://img.shields.io/badge/-development-blue) | | `refs` | refs | ![Development](https://img.shields.io/badge/-development-blue) | ## Network metrics **Description:** System level network metrics captured under the namespace `system.network`. ### Metric: `system.network.packet.dropped` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.network.packet.dropped` | Counter | `{packet}` | Count of packets that are dropped or discarded even though there was no error. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** Measured as: - Linux: the `drop` column in `/proc/net/dev` ([source](https://web.archive.org/web/20180321091318/http://www.onlamp.com/pub/a/linux/2000/11/16/LinuxAdmin.html)) - Windows: [`InDiscards`/`OutDiscards`](https://docs.microsoft.com/windows/win32/api/netioapi/ns-netioapi-mib_if_row2) from [`GetIfEntry2`](https://docs.microsoft.com/windows/win32/api/netioapi/nf-netioapi-getifentry2) **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`network.interface.name`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network interface name. | `lo`; `eth0` | | [`network.io.direction`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network IO operation direction. | `transmit` | --- `network.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `receive` | receive | ![Development](https://img.shields.io/badge/-development-blue) | | `transmit` | transmit | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.network.packet.count` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.network.packet.count` | Counter | `{packet}` | The number of packets transferred. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`network.io.direction`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network IO operation direction. | `transmit` | | [`system.device`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The device identifier | `(identifier)` | --- `network.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `receive` | receive | ![Development](https://img.shields.io/badge/-development-blue) | | `transmit` | transmit | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.network.errors` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.network.errors` | Counter | `{error}` | Count of network errors detected. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** Measured as: - Linux: the `errs` column in `/proc/net/dev` ([source](https://web.archive.org/web/20180321091318/http://www.onlamp.com/pub/a/linux/2000/11/16/LinuxAdmin.html)). - Windows: [`InErrors`/`OutErrors`](https://docs.microsoft.com/windows/win32/api/netioapi/ns-netioapi-mib_if_row2) from [`GetIfEntry2`](https://docs.microsoft.com/windows/win32/api/netioapi/nf-netioapi-getifentry2). **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`network.interface.name`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network interface name. | `lo`; `eth0` | | [`network.io.direction`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network IO operation direction. | `transmit` | --- `network.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `receive` | receive | ![Development](https://img.shields.io/badge/-development-blue) | | `transmit` | transmit | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.network.io` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.network.io` | Counter | `By` | The number of bytes transmitted and received. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`network.interface.name`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network interface name. | `lo`; `eth0` | | [`network.io.direction`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network IO operation direction. | `transmit` | --- `network.io.direction` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `receive` | receive | ![Development](https://img.shields.io/badge/-development-blue) | | `transmit` | transmit | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.network.connection.count` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.network.connection.count` | UpDownCounter | `{connection}` | The number of connections. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`network.connection.state`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The state of network connection [1] | `close_wait` | | [`network.interface.name`](/docs/specs/semconv/registry/attributes/network.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The network interface name. | `lo`; `eth0` | | [`network.transport`](/docs/specs/semconv/registry/attributes/network.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Recommended` | string | [OSI transport layer](https://wikipedia.org/wiki/Transport_layer) or [inter-process communication method](https://wikipedia.org/wiki/Inter-process_communication). [2] | `tcp`; `udp` | **[1] `network.connection.state`:** Connection states are defined as part of the [rfc9293](https://datatracker.ietf.org/doc/html/rfc9293#section-3.3.2) **[2] `network.transport`:** The value SHOULD be normalized to lowercase. Consider always setting the transport when setting a port number, since a port number is ambiguous without knowing the transport. For example different processes could be listening on TCP port 12345 and UDP port 12345. --- `network.connection.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `close_wait` | close_wait | ![Development](https://img.shields.io/badge/-development-blue) | | `closed` | closed | ![Development](https://img.shields.io/badge/-development-blue) | | `closing` | closing | ![Development](https://img.shields.io/badge/-development-blue) | | `established` | established | ![Development](https://img.shields.io/badge/-development-blue) | | `fin_wait_1` | fin_wait_1 | ![Development](https://img.shields.io/badge/-development-blue) | | `fin_wait_2` | fin_wait_2 | ![Development](https://img.shields.io/badge/-development-blue) | | `last_ack` | last_ack | ![Development](https://img.shields.io/badge/-development-blue) | | `listen` | listen | ![Development](https://img.shields.io/badge/-development-blue) | | `syn_received` | syn_received | ![Development](https://img.shields.io/badge/-development-blue) | | `syn_sent` | syn_sent | ![Development](https://img.shields.io/badge/-development-blue) | | `time_wait` | time_wait | ![Development](https://img.shields.io/badge/-development-blue) | --- `network.transport` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `pipe` | Named or anonymous pipe. | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | | `quic` | QUIC | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | | `tcp` | TCP | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | | `udp` | UDP | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | | `unix` | Unix domain socket | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | ## Aggregate system process metrics **Description:** System level aggregate process metrics captured under the namespace `system.process`. For metrics at the individual process level, see [process metrics](process-metrics.md). ### Metric: `system.process.count` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.process.count` | UpDownCounter | `{process}` | Total number of processes in each state. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`process.state`](/docs/specs/semconv/registry/attributes/process.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The process state, e.g., [Linux Process State Codes](https://man7.org/linux/man-pages/man1/ps.1.html#PROCESS_STATE_CODES) | `running` | --- `process.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `defunct` | defunct | ![Development](https://img.shields.io/badge/-development-blue) | | `running` | running | ![Development](https://img.shields.io/badge/-development-blue) | | `sleeping` | sleeping | ![Development](https://img.shields.io/badge/-development-blue) | | `stopped` | stopped | ![Development](https://img.shields.io/badge/-development-blue) | ### Metric: `system.process.created` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.process.created` | Counter | `{process}` | Total number of processes created over uptime of the host. | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | ## `system.memory.{os}.` - OS Specific System Memory Metrics Instrument names for system level metrics that have different and conflicting meaning across multiple OSes should be prefixed with `system.{os}.` and follow the hierarchies listed above for different entities like CPU, memory, and network. For example, [UNIX load average](https://wikipedia.org/wiki/Load_(computing)) over a given interval is not well standardized and its value across different UNIX like OSes may vary despite being under similar load: > Without getting into the vagaries of every Unix-like operating system in > existence, the load average more or less represents the average number of > processes that are in the running (using the CPU) or runnable (waiting for > the CPU) states. One notable exception exists: Linux includes processes in > uninterruptible sleep states, typically waiting for some I/O activity to > complete. This can markedly increase the load average on Linux systems. ([source of quote](https://github.com/torvalds/linux/blob/e4cbce4d131753eca271d9d67f58c6377f27ad21/kernel/sched/loadavg.c#L11-L18), [linux source code](https://github.com/torvalds/linux/blob/e4cbce4d131753eca271d9d67f58c6377f27ad21/kernel/sched/loadavg.c#L11-L18)) An instrument for load average over 1 minute on Linux could be named `system.linux.cpu.load_1m`, reusing the `cpu` name proposed above and having an `{os}` prefix to split this metric across OSes. [DocumentStatus]: /docs/specs/otel/document-status [MetricRecommended]: /docs/specs/semconv/general/metric-requirement-level.md#recommended [MetricOptIn]: /docs/specs/semconv/general/metric-requirement-level.md#opt-in ### Metric: `system.memory.linux.available` | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.memory.linux.available` | UpDownCounter | `By` | An estimate of how much memory is available for starting new applications, without causing swapping. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** This is an alternative to `system.memory.usage` metric with `state=free`. Linux starting from 3.14 exports "available" memory. It takes "free" memory as a baseline, and then factors in kernel-specific values. This is supposed to be more accurate than just "free" memory. For reference, see the calculations [here](https://superuser.com/a/980821). See also `MemAvailable` in [/proc/meminfo](https://man7.org/linux/man-pages/man5/proc.5.html). ### Metric: `system.memory.linux.shared` This metric is [opt-in][MetricOptIn]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.memory.linux.shared` | UpDownCounter | `By` | Shared memory used (mostly by tmpfs). [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** Equivalent of `shared` from [`free` command](https://man7.org/linux/man-pages/man1/free.1.html) or `Shmem` from [`/proc/meminfo`](https://man7.org/linux/man-pages/man5/proc.5.html)" ### Metric: `system.memory.linux.slab.usage` This metric is [recommended][MetricRecommended]. | Name | Instrument Type | Unit (UCUM) | Description | Stability | Entity Associations | | -------- | --------------- | ----------- | -------------- | --------- | ------ | | `system.memory.linux.slab.usage` | UpDownCounter | `By` | Reports the memory used by the Linux kernel for managing caches of frequently used objects. [1] | ![Development](https://img.shields.io/badge/-development-blue) | [`host`](/docs/specs/semconv/registry/entities/host.md#host) | **[1]:** The sum over the `reclaimable` and `unreclaimable` state values in `memory.linux.slab.usage` SHOULD be equal to the total slab memory available on the system. Note that the total slab memory is not constant and may vary over time. See also the [Slab allocator](https://blogs.oracle.com/linux/post/understanding-linux-kernel-memory-statistics) and `Slab` in [/proc/meminfo](https://man7.org/linux/man-pages/man5/proc.5.html). **Attributes:** | Key | Stability | [Requirement Level](/docs/specs/semconv/general/attribute-requirement-level/) | Value Type | Description | Example Values | | --- | --- | --- | --- | --- | --- | | [`system.memory.linux.slab.state`](/docs/specs/semconv/registry/attributes/system.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Recommended` | string | The Linux Slab memory state | `reclaimable`; `unreclaimable` | --- `system.memory.linux.slab.state` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used. | Value | Description | Stability | | --- | --- | --- | | `reclaimable` | reclaimable | ![Development](https://img.shields.io/badge/-development-blue) | | `unreclaimable` | unreclaimable | ![Development](https://img.shields.io/badge/-development-blue) |