Investigating Memory Management in OS X
As I’ve mentioned a few times, I’ve been trying to debug memory usage in an application running under OSX. I’m pretty sure I’ve conquered all the memory leaks, but I’m still not 100% on what some of the definitions are, but here are some things I have learned:
1) Running inside the debugger from xcode (a.k.a. just go hit the big shiny ‘Run’ button or cmd+r takes about 50% more memory (or more) than without.
2) Running inside the profiler takes 3-4x as much memory as running normally. This does not include all the truckload of memory that Instruments will allocate while storing every piece of transient memory that your application starts using. (In my case, though my runtime memory is small, the amount that is transient while doing a lot of network i/o is large, and instruments gets very big, very quickly)
3) I still don’t really understand what Virtual Private Memory is. I’m pretty sure I have solved all of my memory leak problems, but I can’t find anything that really explains that breakdown (from Activity Monitor) very well.
Some numbers (not including when run under instruments):
Time : Real Mem / Private Mem / Virtual Private Mem
In Debugger:
6:00 : 36.0 MB / 5.8 MB
6:10 : 35.0 MB / 7.4 MB
6:20 : 32.9 MB / 8.2 MB / 58.2 MB
6:30 : 36.4 MB / 7.7 MB / 61.4 MB <— shut down another application, memory increased
6:40 : 36.6 MB / 10.0 MB / 61.4 MB
6:50 : 37.3 MB / 10.8 MB / 62.4 MB
7:00 : 38.1 MB / 9.3 MB / 62.4 MB
Outside Debugger:
9:30 : 21.8 MB / 6.8 MB / 59.8 MB
10:00: 28.2 MB / 11.8 MB / 55.4 MB
10:30: 31.4 MB / 12.5 MB / 56.9 MB
After Bug Fix:
11:00: 21.1 MB / 6.0 MB / 60.3 MB
11:15: 23.3 MB / 7.9 MB / 61.1 MB
11:30 21.2 MB / 8.0 MB / 53.9 MB
2:00: 30.0 MB / 11.5 MB / 60.1 MB
2:30: 30.9 MB / 10.3 MB / 60.1 MB
3:00: 31.3 MB / 10.9 MB / 61.1 MB
3:30: 31.3 MB / 10.9 MB / 61.1 MB
4:00: 31.3 MB / 10.9 MB / 61.1 MB
4:30: 31.3 MB / 10.9 MB / 61.1 MB
I am pretty sure all the leaks are gone, but it seems like it doesn’t like to free memory once it is allocated very often, too. Maybe someone who has more knowledge can comment?
