iPad内存使用量不断增加

Question

I'm writing an iPad application that uses a lot of video and large PNG animation sequences, taking care to release all resources when they are no longer needed. Instruments shows no memory leaks, and allocations shows the app never allocates more than about 30 MB. However, when I look at Activity Monitor, I see that the real memory and virtual memory is constantly increasing the more one delves into the application's content. I put NSLogs in all of my dealloc methods, and every object I release is being deallocated. My app, however, is getting killed with a signal 0. Does anyone have any suggestions?

Answer 1

You may be doing this already, but when using the Allocations instrument, take "Heap Shots" as you interact with the UI. This will give you an idea of what's being allocated during each interval and the object's lifecycle. Bill Bumgarner has an excellent blog entry about this powerful tool that's well worth a read.

Answer 2

Could it be that you have NSZombieEnabled? Happened to me one time...

Answer 3

The WWDC 2011 session 318 video "iOS Performance in Depth" (about 43 min 50 seconds into it) describes how animating UIImage(s) in UIImageView can use up lots of memory. They suggest when animating large images using

- (void) animateImages
{
   CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(animateImage:)];
}

- (void) animateImage:(CADisplayLink *)link
{
   [imageView setImage:[UIImage imageWithContentsOfFile:nextImagePath()]];
}

The animation speed isn't guaranteed. Using +[UIImage imageWithContentsOfFile:] is key since +[UIImage imageNamed:] will cache image instances.

I've used this technique in my app that kept running out of memory switching between sets of large image animations and things are working fine and smooth on an iPhone 3GS and iPhone 4S. It's slow on the iPhone 3GS but the 3GS couldn't even do one set of animations before. Looking at the Dirty Size stat in VM Tracker the difference is dramatic.