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TracerBench: Noise Mitigation Techniques

As a general rule of thumb to "zero-out" your environment its recommended you close/exit:

  • all running applications other than those strictly needed to run a test, (osx menu bar & dock)
  • software updates, file syncing, browser-tabs, (osx spotlight & notification: do not disturb "on" )
  • when manually running tests and not using the default headless chrome. be sure to exit all browser extensions

Background Daemons

Daemons are processes that run continuously in the background performing functions required by other processes. It's not explicitly necessary to kill all running daemons - just the ones consuming large amounts of resources and those that are likely to run a spike process for example OSX updater or Chrome updater.

Some common running daemons such as Dropbox, Google, Adobe, Backblaze, Carbonite, CrashPlan more than likely should be exited before running a trace.

To quickly scan your environment for running processes run in a terminal window:

ps -eo pcpu,pid,user,args | sort -k 1 -r -n | head

Then kill the process in question by finding the process-id from the previous command and run in a terminal window:

kill -2 <PROCESS-ID>

SSH (If you have multiple PCs)

The most effective way of mitigating the noise is running tests on a separate machine with Linux server. Visual Studio Code has great SSH capabilities. It's possible to run code editor, browser, and stuff on the primary machine, and have tracerbench and the site running on the Linux server. This way you'll be able to use your browser while tests are running.

OSX

Disable Spotlight

In more recent versions of OSX you cannot disable spotlight without first disabling system integrity protection. This operation comes with risks, please read-up before continuing.

To disable/enable system integrity protection:

  • "Restart" your mac while you hold ⌘R
  • Once you enter recovery mode select "Utilities > Terminal"
  • To disable csrutil disable
  • To enable csrutil enable
  • "Restart" your mac again

Once that's complete, time to disable/enable spotlight from indexing (which is very noisy).

  • From a terminal window
  • To disable sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
  • To enable sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

RHEL 7

Script to stop/start the following jobs

For example: saving this script to something like ~/clean.sh and running chmod a+x clean.sh and then running tracerbench commands eg ./clean.sh tracerbench compare.

#!/usr/bin/bash

sudo service yum-cron stop
sudo service cfengine3 stop
sudo service osad stop
sudo service rhnsd stop

# execute the arguments as a command
$*

sudo service yum-cron start
sudo service cfengine3 start
sudo service osad start
sudo service rhnsd start