In my SharePoint 2013 farm, I was seeing the svchost.exe taking up a lot of memory directly affecting the performance of my site.
There's a great article on How to Troubleshoot svchost.exe Issues to determine what service is the culprit of your memory leak. In my case, it was the Windows Update Service. Since my Windows Updates are controlled by a group policy, I decided to disable this service which solved my performance issues.
Go to Start > Administrative Tools > Services. Right click the Windows Update service. Under Startup type, selected Disabled.