# Intel RDT Input Plugin

The `intel_rdt` plugin collects information provided by monitoring features of
the Intel Resource Director Technology (Intel(R) RDT). Intel RDT provides the
hardware framework to monitor and control the utilization of shared resources
(ex: last level cache, memory bandwidth).

## About Intel RDT

Intel’s Resource Director Technology (RDT) framework consists of:  

- Cache Monitoring Technology (CMT)
- Memory Bandwidth Monitoring (MBM)
- Cache Allocation Technology (CAT)
- Code and Data Prioritization (CDP)

As multithreaded and multicore platform architectures emerge, the last level
cache and memory bandwidth are key resources to manage for running workloads in
single-threaded, multithreaded, or complex virtual machine environments. Intel
introduces CMT, MBM, CAT and CDP to manage these workloads across shared
resources.

## Prerequsities - PQoS Tool

To gather Intel RDT metrics, the `intel_rdt` plugin uses _pqos_ cli tool which
is a part of [Intel(R) RDT Software
Package](https://github.com/intel/intel-cmt-cat).  Before using this plugin
please be sure _pqos_ is properly installed and configured regarding that the
plugin run _pqos_ to work with `OS Interface` mode. This plugin supports _pqos_
version 4.0.0 and above.  Note: pqos tool needs root privileges to work
properly.

Metrics will be constantly reported from the following `pqos` commands within
the given interval:

### If telegraf does not run as the root user

The `pqos` binary needs to run as root.  If telegraf is running as a non-root
user, you may enable sudo to allow `pqos` to run correctly.  The `pqos` command
requires root level access to run.  There are two options to overcome this if
you run telegraf as a non-root user.

It is possible to update the pqos binary with setuid using `chmod u+s
/path/to/pqos`.  This approach is simple and requires no modification to the
Telegraf configuration, however pqos is not a read-only tool and there are
security implications for making such a command setuid root.

Alternately, you may enable sudo to allow `pqos` to run correctly, as follows:

Add the following to your sudoers file (assumes telegraf runs as a user named
`telegraf`):

```sh
telegraf ALL=(ALL) NOPASSWD:/usr/sbin/pqos -r --iface-os --mon-file-type=csv --mon-interval=*
```

If you wish to use sudo, you must also add `use_sudo = true` to the Telegraf
configuration (see below).

### In case of cores monitoring

```sh
pqos -r --iface-os --mon-file-type=csv --mon-interval=INTERVAL --mon-core=all:[CORES]\;mbt:[CORES]
```

where `CORES` is equal to group of cores provided in config. User can provide
many groups.

### In case of process monitoring

```sh
pqos -r --iface-os --mon-file-type=csv --mon-interval=INTERVAL --mon-pid=all:[PIDS]\;mbt:[PIDS]
```

where `PIDS` is group of processes IDs which name are equal to provided process
name in a config.  User can provide many process names which lead to create many
processes groups.

In both cases `INTERVAL` is equal to sampling_interval from config.

Because PIDs association within system could change in every moment, Intel RDT
plugin provides a functionality to check on every interval if desired processes
change their PIDs association.  If some change is reported, plugin will restart
_pqos_ tool with new arguments. If provided by user process name is not equal to
any of available processes, will be omitted and plugin will constantly check for
process availability.

## Useful links

- Pqos installation process: <https://github.com/intel/intel-cmt-cat/blob/master/INSTALL>
- Enabling OS interface: <https://github.com/intel/intel-cmt-cat/wiki>, <https://github.com/intel/intel-cmt-cat/wiki/resctrl>
- More about Intel RDT: <https://www.intel.com/content/www/us/en/architecture-and-technology/resource-director-technology.html>

## Configuration

```toml @sample.conf
# Read Intel RDT metrics
[[inputs.intel_rdt]]
  ## Optionally set sampling interval to Nx100ms. 
  ## This value is propagated to pqos tool. Interval format is defined by pqos itself.
  ## If not provided or provided 0, will be set to 10 = 10x100ms = 1s.
  # sampling_interval = "10"
 
  ## Optionally specify the path to pqos executable. 
  ## If not provided, auto discovery will be performed.
  # pqos_path = "/usr/local/bin/pqos"

  ## Optionally specify if IPC and LLC_Misses metrics shouldn't be propagated.
  ## If not provided, default value is false.
  # shortened_metrics = false

  ## Specify the list of groups of CPU core(s) to be provided as pqos input. 
  ## Mandatory if processes aren't set and forbidden if processes are specified.
  ## e.g. ["0-3", "4,5,6"] or ["1-3,4"]
  # cores = ["0-3"]

  ## Specify the list of processes for which Metrics will be collected.
  ## Mandatory if cores aren't set and forbidden if cores are specified.
  ## e.g. ["qemu", "pmd"]
  # processes = ["process"]

  ## Specify if the pqos process should be called with sudo.
  ## Mandatory if the telegraf process does not run as root.
  # use_sudo = false
```

## Exposed metrics

| Name          | Full name                                     | Description |
|---------------|-----------------------------------------------|-------------|
| MBL           | Memory Bandwidth on Local NUMA Node  |     Memory bandwidth utilization by the relevant CPU core/process on the local NUMA memory channel        |
| MBR           | Memory Bandwidth on Remote NUMA Node |     Memory bandwidth utilization by the relevant CPU core/process on the remote NUMA memory channel        |
| MBT           | Total Memory Bandwidth               |     Total memory bandwidth utilized by a CPU core/process on local and remote NUMA memory channels        |
| LLC           | L3 Cache Occupancy                   |     Total Last Level Cache occupancy by a CPU core/process         |
| LLC_Misses*    | L3 Cache Misses                      |    Total Last Level Cache misses by a CPU core/process       |
| IPC*           | Instructions Per Cycle               |     Total instructions per cycle executed by a CPU core/process        |

*optional

## Troubleshooting

Pointing to non-existing cores will lead to throwing an error by _pqos_ and the
plugin will not work properly. Be sure to check provided core number exists
within desired system.

Be aware, reading Intel RDT metrics by _pqos_ cannot be done simultaneously on
the same resource.  Do not use any other _pqos_ instance that is monitoring the
same cores or PIDs within the working system.  It is not possible to monitor
same cores or PIDs on different groups.

PIDs associated for the given process could be manually checked by `pidof`
command. E.g:

```sh
pidof PROCESS
```

where `PROCESS` is process name.

## Example Output

```shell
> rdt_metric,cores=12\,19,host=r2-compute-20,name=IPC,process=top value=0 1598962030000000000
> rdt_metric,cores=12\,19,host=r2-compute-20,name=LLC_Misses,process=top value=0 1598962030000000000
> rdt_metric,cores=12\,19,host=r2-compute-20,name=LLC,process=top value=0 1598962030000000000
> rdt_metric,cores=12\,19,host=r2-compute-20,name=MBL,process=top value=0 1598962030000000000
> rdt_metric,cores=12\,19,host=r2-compute-20,name=MBR,process=top value=0 1598962030000000000
> rdt_metric,cores=12\,19,host=r2-compute-20,name=MBT,process=top value=0 1598962030000000000
```
