I've got an app that caches a pretty decent amount of data in memory after parsing a csv file, and also displays an MKMapView. After scrolling across the country from one end to the other in the MKMapView, the app inevitably gives me one or more:
Received memory warning. Level=1
Received memory warning. Level=2
and finally crashes due to low memory. I've been trying to figure out a means of managing either the memory of MKMapView or my own data (which comes from a csv file - the csv file needs to be written to frequently, so I'd like to keep it in memory in some fashion or other if possible, unless there is a better means of handling the issue.
Any ideas?
Use instruments to determine how much memory the cached CSV is taking vs the MKMapView. If the CSV is the problem, then look at storing it using CoreData or sqlite.
Related
I search how find my problem.
In my application for iPad when i treat data i have an increase memory and never release that memory, i try instruments leaks memory but that not find memory leaks (i try with profile and analyze).
So my question is they have an other instrument for find memory leaks or other methods?
Thanks in advance for your consideration.
P.S : I don't post code cause that concerned a big part of my code but the part where memory increase is a part where i download from a FTP some zip files (based on SimpleFTPSample from Apple Doc) i unzip this files (with framework minizip) this zip files contains some images and XML files i parse this XML files (around 7200 XML files and 35 000 images files saved) i saved some information (issue of parsing) in data base and that its. If you need part of my code for help me ask me.
Make sure if you have Zombies turned off in Scheme:Diagnostics. With Zombies on no memory is ever deleted. Testing for memory leakage should always be done with Zombies off.
This usually happens when you keep the objects in a datastructure (NSDictionary, NSArray, eg), even after you don't need them anymore. Check with Instruments' Allocations which objects are accumulated, and check in your code where you keep instances of those objects.
Another cause could be long-running threads.
If the loading and parsing you mentioned are done in a single thread that takes a long time, then you may need to do #autoreleasepool in a loop somewhere to force temporary objects to be cleaned up regularly.
It might also be no problem at all. You say you load a lot of images. Images are by default cached by iOS, and only released when necessary to clean up memory. If Instruments "Trace Highlights" shows a lot of memory usage, but "Allocations" doesn't, then this is likely the cause.
I have been having some memory problems with an app. Im getting to a stage now where nothing really gives me a solid answer in terms of memory.
At first I used the Allocations profiler which I dont think seems to work that well at all, I think this is due to the fact most of my code is in Obj-C++ meaning it cant track the memory correctly.
With the Allocations profiler it tells me the app uses 32mb of memory and around this point it says it has low memory and sometimes crashes out. However, within other parts of the applications its used up to 40mb and never crashed out.
I found this code chunk:
http://landonf.bikemonkey.org/code/iphone/Determining_Available_Memory.20081203.html
Which appears to tell me im using 70mb of memory, when I get the low memory warning it says I have 2mb - 4mb left of unused memory. Which seems more reasonable, but its almost double what the profiler says!
The only thing I can think of is just ignoring it all and reducing the amount of memory used by my app as much as possible.
Ignore it all and reduce the size of your app is actually a good way to proceed. Make sure that you're responding to memory warnings by purging anything in memory that you don't need. Remember that different devices have different amounts of memory, and you may need to use even less than you think, at least if you want to support those older devices.
I'm loading a couple of large csv files when my app loads for the first time and this works fine on the simulator but when running on my phone it crashes about 30% through with the message 'Program received signal "0"' which implies a memory crash. However, when I put a breakpoint in the didReceiveMemoryWarning event it doesn't seem to be called.
Am I missing anything or will the program normally shut down without the event being called?
If you're loading the file in a synchronous call on your app's main thread, that would prevent it from receiving other messages (such as memory warnings) before the synchronous call completes. Try making loading the CSV files an asynchronous task. (A good starting point would be reading up on NSOperation.) That will allow your app to receive memory warnings during the loading process.
What's happen if you try loading small csv instead. If it work fine then your csv is too large and cause memory issue. If so you may have to read the csv file chunk by chunk and release the memory of the old one before reading the new one.
I build a parsing algorithm using NSXMLParser.
Im having doubt as to what is the best strategy for keeping my memory usage on a minimum.
I have a valueObject (e.g. "Person") this object has ≈ 30 NSString properties, while parsing the xml I continually alloc and release a temporary Person object as the nodes are traversed.
I checked this and there is only one of these Person objects instantiated at any time.
When a node is traversed and a Person is "build" I pass the Person to a NSMutableArray and release this Person. Seems no problem there. (I'll need the array for a tableView).
When I reach around 50+ Person objects in the array my app just quits, didReceiveMemoryWarning doesn't get called, no other warnings, no parseErrorOccurred, nothing?
If I limit the number of Persons in xml the app does just fine, I haven't been able to find any memory leaks with Instruments.
I think that I simply can't hold 50+ Person objects in an array… seems a bit harsh, but I haven't got much memory experience with the iPhone, so this is just a guess.
The xml is search results from which the user probably only needs a few, so persisting them to my core model to keep them around for display seems a bit crazy.
What would be a good strategy for keeping these Person objects around? or am I missing a huge memory leak since the iPhone should be able to handle much more than this?
Hope some experienced developers can point me in the right direction:)
Thank you!
Despite NSXMLParser being a SAX-based parser it does not support parsing an input stream, which means that the entire XML string you are parsing is kept in memory. This on its own is a big issue, but as you parse the problem gets worse as you start duplicating the string data from the XML in your Person objects.
If your strings are really big, you've got the second problem of having too many parsed Person objects in memory at one time.
The first problem can be solved by using AQXMLParser from Jim Dovey's AQToolkit library, which provides an NSXMLParser-like API but with support for streaming the data from disk.
The second problem can be solved using a disk-based persistence technology, like Core Data, SQLite Persistent Objects, or even just storing the Person objects on disk yourself.
How long are those strings? Generally, on the iPhone 3G and older models, your app should have a minimum of about 20 MB of memory available (much more on the 3Gs). This is no absolute rule, of course, but a decent rule of thumb. To occupy this much memory with 50 objects would mean ~400-500 KB per Person object. Is this in the ballpark? If so, you will probably need a memory management strategy that does not keep all objects in memory at the same time. Core Data can probably help you a great deal in that case.
If you did not receive a memory warning it is probably not the reason your app is quitting. In Xcode go to the organizer, and select the device, then click on the console tab. If they app was shutdown for memory reasons there will be a system message in the console log saying it is killing the app due to memory pressure.
The answer is to chop up the incoming stream, I wrote a post about it some time ago:
https://lukassen.wordpress.com/2010/01/15/feeding-nsxmlparser-a-stream-of-xml/
Can anyone point into the right direction here. I want to respond when my application receives memory warning, (i want to know how to respond to this notification). Plus, How much memory can i wire with my application?
Any articles or book reference would be great. Thanks.
If your app gets a memory warning (such as in your view controller's didReceiveMemoryWarning method) you need to release any non-critical data. Anything that you're using that cached, for example, or that can be regenerated, should be dumped.
For example, if your app crunches some numbers and stores the result in a big array, if you're not actively using that array, you should release it. Then, regenerate it when you need it again.
A little more information is here:
Observing Low-Memory Warnings
I've heard informally that warnings get issued when your application hits about 22 MB. (Any allocated memory is included -- the iPhone keeps everything in physical RAM and doesn't page out to any other storage.) Given that the phone only has 128 MB of total RAM, this seems plausible.
That limit does not include the memory used by shared system libraries, such as the Objective-C runtime. And while I'm not entirely sure on this, I don't think WebKit's memory usage is included for the UIWebView component, as I believe WebKit is always loaded (but again, not 100% sure on that).
The best thing to do when you hit this limit is free anything that you can easily regenerate or re-read from input files, such as views, images, and cached data.