You should see two flags appear on the Instruments timeline. With instruments running exercise the app to get a typical memory footprint and then use the home button to send it into the background. Alternatively you can manually click the Snapshot Now button after the app has entered the background and been suspended to record its memory usage. Since we are not in this case worried about impacting the application performance we can enable the Snapshot Automatically option with the default interval of 3 seconds.
The VM Tracker tool needs to suspend the app whilst taking a snapshot of its virtual memory so by default Apple has not enabled it to automatically snapshot the app. This will launch the application and attach Instruments to the running process with the Allocations and VM Tracker instruments.
To use the VM Tracker instrument run the application on a test device using the Run with Performance Tool > Allocations option from the Xcode Run menu. So this is the memory that needs to be reduced to a minimum if we want to increase the chances of surviving in the background. The “dirty” memory is what counts when an application is moved into the background and suspended.
#Xcode ios memory monitor mac os x
This view is primarily useful as an overview of how a process’ memory is being used, and it is recommended that special attention is paid to the “dirty” sizes, as these represent memory that must be paged to disk under memory pressure on Mac OS X and are completely unreclaimable memory on iPhone OS. Individual regions are grouped by region type and show their contribution to the type’s overall usage statistics. Summary view - This view shows the total amount of memory by region type.
The most interesting piece is on the Summary view: Unfortunately the documentation for VM Tracker does not yet seem to have made it into the Instruments User Guide so you have to look at the iPhone SDK Release Notes for iPhone OS 3.1 for details. Note that you need to be running on Snow Leopard to use VM Tracker. VM TrackerĪ new memory analysis instrument called VM Tracker was added to the Xcode Instruments tool with iPhone OS 3.1 to allow you to examine the virtual memory space of a process. I mentioned the recommendation from Apple to reduce your memory usage when entering background mode without mentioning how you determine what you are currently using. A quick follow up on yesterdays post about adding multitasking support to an iOS 4 app.
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