Use the following command to determine which application pool maps to your w3wp.exe worker instance. This is particularly handy with SharePoint as it has 3 w3wp.exe processes running at any one time by default.
appcmd list wp
This will give you an output similar to the following:
C:\Windows\System32\inetsrv>appcmd list wp
WP "21192" (applicationPool:SharePoint - 80)
WP "12256" (applicationPool:SecurityTokenServiceApplicationPool)
WP "19972" (applicationPool:5f2e9be121504641ae144bcae3b8cf6e)