Xcode Memory Graph - showing increasing memory use - what exactly does it show?

4
votes

When watching the debug graph in xcode 6 (and probably 5 too), when running my application the memory use continues to rise as I place more of a certain object on the screen and animate it's movement. It does not seem to decrease when I remove it. Once removed I believe there are no more references to them.

See screenshot: http://i.stack.imgur.com/SnhbK.png

However when I use Instruments to try to identify what's going on, there's only around 12mb persisting, and Total Bytes continues to rise, as expected.

See screenshot: http://i.stack.imgur.com/VBwce.png

Is this normal behaviour? What exactly is the graph in Xcode showing? Am I overlooking something?

In Instruments I have Allocation Lifespan set to All Allocations and Allocation Type set to All Heap and Anonymous VM for the screenshots above.

UPDATE

By running Instruments with Activity Monitor I was able to see that the "Real Memory" was increasing at the same rate as is displayed in Xcode. @Mark Szymczyk pointed out that OpenGL ES Texture memory allocations are not shown in the Allocations instrument.

By purging the texture cache with the following command in Cocos2D 3.1 at regular intervals, memory use consistently drops back down to around 18mb and begins increasing again as I add more sprites.

[[CCDirector sharedDirector] purgeCachedData];

Credits go to Mark Szymczyk for pointing me in this direction - thanks!

1
iosobjective-cxcodexcode-instruments
Hi JoGoFo, Have you enabled Zombie in your project? - Yogendra
Hey Student, I meant to mention that Zombie is turned off. Any other ideas? - JoGoFo
Hi, Are you using large collection of images in your project ? - iamVishal16
Not a large amount of images, no. Less than 10. I'm more curious to know if I'm looking at this correctly or if I'm missing something - JoGoFo

1 Answers

4
votes

Looking at your screenshots, the Xcode graph is probably showing the equivalent of the Total Bytes column in your Instruments screenshot. When you remove an object, the persistent bytes will decrease, but the total bytes won't. That would explain why the memory use never goes down in the Xcode graph.

The Persistent Bytes column in Instruments is what you should be looking at to determine your app's memory usage.