In win 8 and before there was only about 16 svhost running at any time, as many processes were running under one as a group. I can't remember which version of win 10 they did it in, but now every process that runs has its own service host for the most part, there are still a few groups but no where near as many.
From what i read the spare renderer should only show on the chrome taskmanager, not the windows one.
Use Chrome's built-in Task Manager to see what processes are using up the most resources on your computer and kill ones that stop working.
www.howtogeek.com
so if you do ever see it again, screenshots would be nice.