I'm trying to get a feel for the amount of memory an iOS app can reliably allocate to help me drive some design decisions. The app is going to involve real time synchronised processed audio and animation.
Other than writing code that loads up the frameworks I'll need then trying to progressively allocate memory until I get warnings, is there any way to determine this kind of thing?
The simulator doesn't let you select a specific hardware model, so I assume I can't even simulate this stuff.
You cannot determine how much memory an app allocate as far as I know. Always try to keep the lowest memory possible for your app.
The memory allocated to your app depends on many factors like : number of background process happening, amount of memory available, memory used by other apps, the device you are running etc..
So, its not a good practice to keep a maximum line for memory consumed by your app and design accordingly.
Also try to hold only the necessary memory you need and handle memory issue in the memory callback methods like 'didreceivememorywarning'. Always consider that you have the least amount of memory allocated by the OS.
Related
I am having some trouble around memory leaks in my app.
I just wanted to know that whether it is possible to identify how much memory allocated by my app on heap so that i can reduce my resources accordingly.
I know that system gives low memory warnings & i can clean up my data there but even if sometimes it wont happen.
If i get to know that my app is reaching maximum memory & remaining size on heap so i could be better to reduce my resources.
Thanks in advance....
Use Instruments. Command-I in XCode to profile your app in Instruments.
Yes of course, I would recommend the instrument's tool "Leaks". It lets you know how much memory allocates your app, and if there are leaks it tells you what they are, when and were it was allocated (and obviously not released).
Here is a nice guide I used some time ago.
http://www.cimgf.com/2008/04/02/cocoa-tutorial-fixing-memory-leaks-with-instruments/
Is there a way to retrieve information about the memory of the ipad during running?
For example, i would like to print in the console the use of memory at t instant.
Thanks
You should instrument this instead of trying to print a number. That number is not really useful. What you care about is your application's dirty memory footprint for memory pressure on the device and how much code/mapped ro mem you're evicting to see if you're essentially thrashing and causing performance problems due to memory pressure.
The other info you can get, like device inboard memory and how many pages your app has allocated are not useful because you don't know how much of that memory is wired to other devices or the kernel and you don't know how many of your allocated pages are faults at that point.
I'm planning an application which will involve loading many pictures at one time and thus requires a large chunk of memory. For example, I might have 50 image objects created at once, taking a total of 1GB of RAM. But when the user goes to load 20 more pictures, I'd like to make sure that amount of memory is already reserved and ready.
Now this part might seem a little backwards from normal. Rather than specifying how much memory my application shall reserve, instead I need to specify how much memory to leave free for other applications, and adjust my application's memory periodically according to this specification. I must say I've never worked with reserving memory at all, and especially won't know how to leave this remaining available memory.
So for example, if the computer has 2048 MB of RAM, and the option is set to leave 50 MB free for other applications, and there is already 10MB of RAM being used by other apps, then it should reserve 2048-50-10 = 1988 MB for my app.
The trouble I foresee is suppose the user opens another application which requires 1GB. My app has to catch this and shrink its self.
Does this even sound like a feasible approach? Basically, I need to make sure there is as much memory reserved as possible at any given time, while leaving a decent amount available for other apps. Would it make a significant impact on performance if I do this, or not much at all? I might be loading and unloading images at rapid paces, and I don't want it to reserve/free this memory on demand, I want it to stay reserved.
+1 for Sertac's mentioning of how SQL Server rides the line of allocating memory it needs, but releasing memory when Windows complains.
Applications can receive Window's complaints by using the CreateMemoryResourceNotification:
hLowMemory := CreateMemoryResourceNotification(LowMemoryResourceNotification);
Applications can use memory resource notification events to scale the
memory usage as appropriate. If available memory is low, the
application can reduce its working set. If available memory is high,
the application can allocate more memory.
Any thread of the calling
process can specify the memory resource notification handle in a call
to the QueryMemoryResourceNotification function or one of the wait functions.
The state of the object is signaled when the specified
memory condition exists. This is a system-wide event, so all
applications receive notification when the object is signaled. Note
that there is a range of memory availability where neither the
LowMemoryResourceNotification or HighMemoryResourceNotification object
is signaled. In this case, applications should attempt to keep the
memory use constant.
But it's also worth mentioning that you might as well allocate memory that you need. Your operating system has a very sophisiticated set of algorithms to swap out the least used memory when memory pressure is high. You can take advantage of this by simply allocating all the memory that you need. When Windows starts to run low, it will find those pages of memory that you are using the least and swap them out to disk. (This is how a well-known reverse proxy works).
The only thing left is to decide if you want to free some images when Windows says it's running low on RAM. But if you're not using the memory, it is going to be swapped out to disk for you.
It's not realistic to account for other apps. Just ignore them. The system will page things in and out as needed. If you really wanted to do this you'd have to dynamically adapt to other processes as they start and finish. That's really not realistic. What's more it's not practical to inquire of other processes how much memory they need. Leave it all to the system.
Set a budget for your app and make sure you don't exceed it. Keep the most recently used images in memory and when you approach your memory budget throw away the least recently used images to make space.
If you are stressing the available resources then make sure you use FastMM and enable LARGE_ADDRESS_AWARE for your app so that you get 4GB address space when running on a 64 bit OS.
Can someone suggest to me a way to count (inside an iOS app) all open apps on OS, to show to the user an alert if there's not enough memory to run my app?
While theoretically this is possible, it's not a good idea. First of all, the number of open apps is an inadequate measure when in fact you care about memory consumption. Next, this doesn't take into account the fact that different devices have different amounts of memory. Last but not least, if memory is running tight iOS will first kill background applications and free some memory for you.
So, don't do it. Instead, try to be a better iOS citizen: respond to memory warnings, try to cache stuff in files and read up on memory mapping (for example with mmap) to reduce your app's memory footprint.
I'm developing an iOS application which (like any other) requires a certain amount of free memory to run correctly. In my case - at least 4MB, I cannot use any less than that. It's a fairly small amount, but a few times (on my device at least) I got only 2MB free and the program crashed. What do you think is the best way to tell users how much memory you need. I know the code to get the currently available memory, but even if I tell the user (like in a UIAlertView when the user starts the program) that he is running low, what can I suggest him to do to free more memory (except turning off and on the device). Any ideas?
On older devices you can't really rely on getting more than 8MB. 4MB is a great target, and if through your profiling you've determined that's all you need, you should be fine.
However, I think the concept here is that if you receive memory warnings you wouldn't bother the user with those types of things. I would find it pretty annoying myself. It would be better to limit your app's activity or throttle back whatever you are doing that is so memory intensive.
On which kinds of iPhone devices your app is being tested? I suppose that the iOS has to do its job well to free enough memory for you or kill alll background app so it can have more memory