roblem: NodeRunner.exe is consuming a lot of memory and CPU resulted in performance issues on SharePoint 2013 server.

Solution:
NodeRunner.exe is a SharePoint 2013 Search service component and it is resource hungry. To reduce the CPU and Memory impact of this process, follow below steps:

Step 1: Reduce the CPU impact of the search service
By default SharePoint search uses "maximum" to speed up its search crawling process. To reduce the CPU usage of the search service, run this PowerShell script from any one of your SharePoint 2013 server:

Set-SPEnterpriseSearchService -PerformanceLevel Reduced

Step 2: Limit the NodeRunner.exe's Memory usage: 

• Open the configuration file at "C:\Program Files\Microsoft Office Servers\15.0\Search\Runtime\1.0\noderunner.exe.config" 
• Locate the node "nodeRunnerSettings", Set the value for "memoryLimitMegabytes" attribute to specific value (E.g. 1024). By default its value is 0 (which means unlimited memory). 
  

Step 3: Restart Search Service
For the above steps to take effect, You have to restart SharePoint 2013 search service. Go to Services console, restart SharePoint Search Host Controller process. Or use the PowerShell cmdlet to restart Search host controller process:

Restart-Service SPSearchHostController

PowerShell to Set NodeRunner config:

#NodeRunner File Path
$NRFile= "C:\Program Files\Microsoft Office Servers\15.0\Search\Runtime\1.0\noderunner.exe.config"
 
#Get the XML
$NodeRunnerConfig = New-Object XML
$NodeRunnerConfig.Load($NRFile)
 
#Set Limit to 100 MB
$NodeRunnerConfig.configuration.nodeRunnerSettings.memoryLimitMegabytes = "100"
$NodeRunnerConfig.Save($NRFile)