Re: Memory Allocation Question
Re: Memory Allocation Question
- Subject: Re: Memory Allocation Question
- From: Quincey Morris <email@hidden>
- Date: Mon, 28 Feb 2011 20:55:30 -0800
On Feb 28, 2011, at 19:49, Laurent Daudelin wrote:
> When I run my app, scanning my home folder, the memory consumption will go in the 300MB range. Even when I release all the objects I have been allocating, Activity Monitor reports the same amounts of real, virtual and private memory. Those amounts don't go down.
Activity Monitor numbers need to be interpreted *very* carefully. Virtual memory, for example, isn't about how much memory you're using, but how much virtual memory *address space* you're using, whether or not it's actually using memory for all the address space.
> So, I ran my app a few times in Instruments. When I clear all objects I've been using, I am left with about 12KB of leaked memory.
The amount of leaked memory doesn't correlate to the total amount of memory being used (unless you have a rampant runaway). You may have false positives and false negatives, so the Instruments data can be hard to interpret too.
> How can Activity Monitor reports the same numbers while Instruments seems to report what's actually happening? I wouldn't have much problem with my app kinda keeping the same memory it used in subsequent runs but when I do another run, the memory used keeps going up, e.g. it doesn't seem to stabilize.
I'd suggest you give heapshot analysis a try, as in this great B.Bum blog post:
http://www.friday.com/bbum/2010/10/17/when-is-a-leak-not-a-leak-using-heapshot-analysis-to-find-undesirable-memory-growth/
That way you can first eliminate real leaks*, and then start looking at whether your overall usage is excessive even if not leaky.
*And heapshot analysis should help you home in on what's getting allocated each run, even if that doesn't turn out to be any kind of leak.
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