proxy_cache_bypass $http_upgrade;

I have some web applications that suggest using the below 2 lines for NGINX reverse proxying:

 proxy_set_header Upgrade            $http_upgrade;
 proxy_set_header Connection         $connection_upgrade;

I sometimes see the below line paired up with the above 2 lines in various examples online:

 proxy_cache_bypass                  $http_upgrade;

Is there any benefit to adding the below line to the other lines? Is there any performance gain/loss by adding this line? I'm particularly interested if it increases or decreases performance of any kind.