by default the level is set to maximum when you install the sharepoint search service, Thats because on a live service you expect it to be fast with optimum hardware to support it with the correct topology to break the load from the search service!
setting it to reduced is the correct way go about it:
on dev machine:
Set-SPEnterpriseSearchService -PerformanceLevel Reduced- restart sharepoint search service
on production if hardware is tight than use PartlyReduced
Set-SPEnterpriseSearchService -PerformanceLevel PartlyReduced- restart sharepoint search service
on a live server where the search service is over serveral servers within a farm with 4 cores each with atleast 8gb ram:
leave it as it is:
Set-SPEnterpriseSearchService -PerformanceLevel Maximum- restart sharepoint search service
there is not much difference between partlyreduced and reduced, the difference is the priority is NOT set to high in partlyreduced setting.
Specifies the relative number of threads for the crawl component performance.
The type must be one of the following values: Reduced, PartlyReduced, or Maximum. The default value is Maximum.
Reduced: Total number of threads = 4 number of processors, Max Threads/host = number of processors.
Partly Reduced: Total number of threads = 16 times the number of processors , Max Threads/host = 4 plus the number of processors. Threads are assigned Below Normal priority.
Maximum: Total number of threads = 32 times the number of processors, Max Threads/host = 4 plus the number of processors. Threads are assigned Normal priority.
