Use the libjpeg-turbo library
The libjpeg-turbo library creates jpeg in a more efficient way that the default libjpeg library. To use it in GeoServer, two things must be installed: the library itself and the libjpeg-turbo Map Encoder extension.
Installing the libjpeg-turbo library
To install the library in a Windows machine, follow these steps:
- Download the library installer for the libjpeg-turbo download page 
- Execute the installer and follow the installation instructions. 
 
Installing the Map Encoder extension
- Download the extension for the Geoserver version contained in Geoserver Enterprise from this download link 
- Unzip the downloaded zip file in the - WEB-INF/libdirectory of the GeoServer installation.
- Restart you GeoServer instance for the changes to take effect.