Thanks Gila for Awesome explanation.

Now, I am in a point where I was able to get insight of how sql server memory used by all queries but I feel my original question which I posted is somewhat wrong and I am convinced with what you say and always best practice is to SET max server memory to a value where sql server can play nicely.

Coming, 1 step back. Assuming , I have set the max server memory to 4GB i.e. bpool on my 8GB machine, still if I see external memory pressure. May be mtl or non-buffer pool or any other anti virus scans or any memory hog app running running on the machine might cause memory issues. How would I go further for troubleshooting External memory pressure.

Any links/resources that can shared will be great help.