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Darwin Runtime Monitor

Monitor information from system tooling and alert upon reaching configurable threshold levels

This tool is not affiliated with or endorsed by Apple

Screenshots

Increased Swap usage alerts

Example image removed

Increased Kernel CPU usage

Example image removed

Structure

This tool consists of three parts

  1. Scitps that query, process and alert, eg. swapusage.sh or kernelcpu.sh
  2. Main script that aggregates all other processor scripts (1), ie. runtime_monitor.sh
  3. Scheduler manifest that is linked to the standard Launchd location and executes the main script (2) at defined intervals - com.darwinruntime.monitor.plist

Installation

Download

curl -LO https://github.com/spekulant/darwin-runtime-monitor/releases/latest/download/darwin-runtime-monitor.zip
curl -LO https://github.com/spekulant/darwin-runtime-monitor/releases/latest/download/darwin-runtime-monitor.zip.sha256

Verify the integrity of the package

shasum -a 256 -c darwin-runtime-monitor.zip.sha256

Install the package

unzip darwin-runtime-monitor.zip
cd darwin-runtime-monitor
./install.sh

the install.sh script will overwrite any previous version in ~/.runtime-monitor and so will also be the same script you can use to upgrade to a new version.

Uninstall

Just run ./uninstall.sh

Monitored values

SWAP usage

This script makes use of sysctl to extract information about current SWAP usage.

Too high levels of SWAP usage indicate the system ran out of memory and started allocating information on your disk - which is several times slower than RAM. This usually leads to system slowness.

When the script notices there is x >= 512MB of SWAP allocated, it sends the first notification saying the SWAP usage is rising and that you might consider closing some apps.

Example image removed

At the level of x >= 1000MB it sends a notification alert saying the usage is high. You'd most probably feel the system to be sluggish at this point anyway, and this notification will just help you pinpoint the issue and take action before even more memory is commited to SWAP.

Kernel CPU usage

High Kernel CPU usage should be quite unusual and indicates an issue that may have to be remediated as a priority. In this state, the kernel starves other processes and leads to general system slowness.

When the Kernel CPU usage reaches ~40%, the tool issues the first notification saying the Kernel CPU usage is increasing

Example image removed

This can be down to various reasons, one that I encounter relatively often is USB-C adapters. Sometimes it's enough to just plug the adapter into a different port, sometimes switching it to the other side works. If nothing helps, it may just be a case of plain incompatibility.

Parameters

  • ~/.runtime-agent/swapusage.sh: MEDIUM_THRESHOLD = 512 ( MB )
  • ~/.runtime-agent/swapusage.sh: HIGH_THRESHOLD = 1000 ( MB )
  • ~/.runtime-agent/kernelcpu.sh: MEDIUM_THRESHOLD = 40 ( %CPU )
  • ~/.runtime-agent/kernelcpu.sh: HIGH_THRESHOLD = 100 ( %CPU )
  • ~/.runtime-agent/com.darwinruntime.monitor.plist: StartInterval = 900 ( every 15 mins )

Troubleshooting

  1. Try running the main script manually. It is expected it should take a few seconds to run - if it exits immediately, the issue would be somewhere downstream.
~/.runtime-monitor/runtime_monitor.sh

If it exits after ~3 seconds without any errors, then the issue may be upstream - in the Launchagent configuration:

  1. Try running the launchd process manually
launchctl start com.darwinruntime.monitor

You can see the status of the task with launchctl list | grep darwinruntime

- 78 com.darwinruntime.monitor

The number is the exit code the task returned, so anything other than 0 is some kind of error

You can inspect the error code with launchctl error <code>

$ launchctl error 78
> `78: Function not implemented`

You can also lookup the logs to try and find something relevant

grep darwinruntime /var/log/com.apple.xpc.launchd/launchd.log

It may take some digging but eventually something readable should surface

Service could not initialize: access(/Users/tomaszsobota/runtime-monitor/runtime_monitor.sh, X_OK) failed with errno 2 - No such file or directory, error 0x6f - Invalid or missing Program/ProgramArguments

While at it, we can also lint the plist file to be 100% sure this is not due to any obvious errors

$ plutil -lint com.darwinruntime.monitor.plist
> com.darwinruntime.monitor.plist: OK

This particular issue was fixed by swapping the ProgramArguments with a simplified Program definition, then we have to boot out the current failed execution and load the new one again:

launchctl unload ~/Library/LaunchAgents/com.darwinruntime.monitor.plist
launchctl load ~/Library/LaunchAgents/com.darwinruntime.monitor.plist

License

Creative Commons - Attribution 4.0 International as per the LICENSE file