I’m using instruments to tracking memory usage. Heapshot Analysis is awesome, but I also found some “non-object”. what’s this? kind of abandoned memory or something else ? How to solve this ?

Another Question may relate,
I used to use
[myObj release], myObj = nil;
myObj = [[MyObj alloc] init];
to release object and create a new one. (myObj = nil, just for avoid crash)
Some guy said, It may waste memory performance. Is he right?
I want to know some details.
Very appreciate for your help.
Your question has an answer here:
What does <non-object> in Allocation "heapshots" mean?
For the memory management there’s absolutely nothing wrong in your code. myObj = nil is pointless because you’re allocating a new object in the line after it.