---
name: "pmdanixl"
section: "1"
platform: "linux"
package: "pcp"
version: "7.2.2-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/pmdanixl"
---

# pmdanixl(1)

NVIDIA NIXL Performance Metrics Domain Agent

## NAME

**pmdanixl** - NVIDIA NIXL Performance Metrics Domain Agent

## SYNOPSIS

**$PCP\_PMDAS\_DIR/nixl/pmdanixl**

## DESCRIPTION

**pmdanixl** is a Performance Co-Pilot (PCP) Performance Metrics Domain Agent (PMDA) that collects performance telemetry from one or more running NIXL (NVIDIA Inference Xfer Library) agents.

NIXL agents write per-event telemetry into shared-memory ring buffers located in the directory specified by the **NIXL\_TELEMETRY\_DIR** environment variable (default **/var/tmp**). The PMDA discovers agent files in that directory, drains new events on each fetch, and accumulates them into per-agent running counters. Each discovered agent appears as a separate instance in the **nixl.agents** instance domain, so metrics from different agents can be monitored independently.

Metrics are organised into four groups:

- **nixl.transfer.\***

  Data transfer byte and request counts (TX and RX).

- **nixl.memory.\***

  Memory registration and deregistration sizes.

- **nixl.performance.\***

  Accumulated transfer time measurements (in microseconds).

- **nixl.errors.\***

  Error event counts, broken down by error type.

## NIXL CONFIGURATION

NIXL telemetry is disabled by default. The following environment variables must be set in each NIXL application process before it creates its agent for telemetry data to be written to shared memory and discovered by this PMDA.

- **NIXL\_TELEMETRY\_ENABLE=1**

  Activates telemetry collection. Accepted values are **1**, **yes**, **on**, **true**, or **enable** (case-insensitive).

- **NIXL\_TELEMETRY\_DIR=*dir***

  Directory in which NIXL writes its shared-memory telemetry files, one file per agent, named after the agent name supplied at agent creation time. This must match the **telemetry\_dir** setting in *$PCP\_SYSCONF\_DIR/nixl/nixl.conf*. Defaults to **/var/tmp**.

- **NIXL\_TELEMETRY\_BUFFER\_SIZE=*N***

  Number of events the ring buffer can hold before older events are silently overwritten. Increase this value if the application produces bursts of telemetry faster than the PMDA drains them. Defaults to **4096**.

- **NIXL\_TELEMETRY\_RUN\_INTERVAL=*ms***

  Flush interval in milliseconds used by the NIXL exporter thread. Defaults to **100**.

A minimal setup for a single application is:

```
export NIXL_TELEMETRY_ENABLE=1
export NIXL_TELEMETRY_DIR=/var/tmp
./my_nixl_application
```

With multiple applications writing to the same directory, each agent file will be discovered automatically and reported as its own instance. The PMDA user (set via **user** in *nixl.conf*) should match the user running the NIXL applications so that file permissions align without requiring world-writable telemetry files.

## INSTALLATION

Once NIXL applications are configured to export telemetry, install the PMDA:

```
# cd $PCP_PMDAS_DIR/nixl
# ./Install
```

If **NIXL\_TELEMETRY\_DIR** is not the default **/var/tmp**, set it in the environment before running **Install** so it is recorded in the PMDA's startup configuration.

To verify the PMDA is running and instances are visible:

```
$ pminfo -t nixl
$ pminfo -f nixl.transfer.tx_bytes
```

## REMOVAL

```
# cd $PCP_PMDAS_DIR/nixl
# ./Remove
```

## ENVIRONMENT

- **NIXL\_TELEMETRY\_DIR**

  Overrides **telemetry\_dir** from *nixl.conf* at runtime. Defaults to **/var/tmp**.

## FILES

- *$PCP\_SYSCONF\_DIR/nixl/nixl.conf*

  PMDA configuration file.

- *$PCP\_PMDAS\_DIR/nixl/Install*

  Installation script.

- *$PCP\_PMDAS\_DIR/nixl/Remove*

  Removal script.

- *$PCP\_LOG\_DIR/pmcd/nixl.log*

  PMDA log file.

## PCP ENVIRONMENT

Environment variables with the prefix **PCP\_** are used to parameterize the file and directory names used by PCP. On each installation, the file */etc/pcp.conf* contains the local values for these variables. The **$PCP\_CONF** variable may be used to specify an alternative configuration file, as described in [**pcp.conf**(5)](/pcp.conf/5.md).

## SEE ALSO

[**PCPIntro**(1)](/PCPIntro/1.md), [**pmcd**(1)](/pmcd/1.md), [**pminfo**(1)](/pminfo/1.md), [**pmval**(1)](/pmval/1.md) and [**PMDA**(3)](/PMDA/3.md).