CODEWITHSUNDEEP
iosipaddebuggingmemoryinstruments
Tobias Domhan
Tobias Domhan

Reputation: 3286

ios instruments vm tracker IOKit insane residence size

I've just been analyzing an ipad app I'm developing using Instruments. In particular I was interested in the memory usage, as I have been receiving some memory warnings.

First of all the Activity monitor reports overall some 40MB of memory used just after starting the application. This really seams like a lot to me. Especially as after the startup nothing really fancy is going on.

So I have been analyzing the app in the VM tracker.

First of all can somebody explain how to interpret the dirty memory? I mean the ipad doesn't really have virtual memory, in the sense that there is no swapping etc.

Ok the really weird thing is that I have some 40 MB of dirty memory, that is resident! Some 38MB are listed under IOKit. Under IOKit there is no further information, what that actually means.

So what exactly does IOKit do? What could be causing this insane those huge values?

Any kind of hint is appreciated! :)

Upvotes: 2

Views: 2557

Answers (2)

RY_ Zheng
RY_ Zheng

Reputation: 3427

What is dirty memory?

According to this session.

  • memory written by an app
  • all heap allocations
  • decoded image buffers

VM profile shows some info of the dirty memory

like dirty memory size. They are anonymous. 

vmmap --summary App.memgraph

In this session, this Apple dev uses heap to get more info about the object sizes. 

heap App.memgraph

enter image description here

Upvotes: 0

zaph
zaph

Reputation: 112857

Try Heapshot Analysis, bbum has a great tutorial here.

Basically you take a Heapshot, run some procedure, take another Heapshot for several iterations. This will help find memory that lost but not a leak. I use this method often,

I have used Heapshot many times to great advantage, many thanks to bum.

Upvotes: 1

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