I have completed my first iOS app. Its parsing and an rss feed and showing titles, date, creator name and images in a tableview. Now i am trying to check its performance before submitting it for the approval. I am using Xcode instruments for the very first time. I have first checked and removed all the leaks and now there are no memory leaks in the app. Now i am using Allocations. Here is how it looks like:
Since i am using it for the very first time i am not sure about many things. Overall Bytes looks too large to me and i need to ask whether is there any limit or not which i can use? and should i look for overall bytes or live bytes or anything else?
Thanks
Overall bytes includes those that have been released and is a running total of what has been allocated to your app during the lifetime of the app. The Live Bytes is the one to really worry about as that is the one that shows bytes that are currently allocated.
Overall bytes could keep going on forever as long as you release stuff and the Live Bytes doesn't go too high then you will have no problems.
From that screenshot live bytes looks ok.
There are more details here XCode Instruments Allocations: Look at Live Bytes or Overall Bytes?
Related
Users are complaining that my app is slow sometimes, so I did allocations profile, check attached image below, Live bytes is around 35 MB.
Is 35 MB fine or I have to lower it?
What's the best Live bytes?
I see ImageIO_PNG_Data & JS garbage collector have the biggest allocation.
How can I clear them?
Thanks
P.S. I'm using ARC
You're looking in the wrong place. To determine why your application is slow, you will need to use one of the CPU instruments (e.g, Time Profiler), not memory allocation.
I'm in the process of understanding how to put instruments to better use. I just finished a leak management exercise, and instruments is reporting very few leaks. I'll figure those out later. In the mean time, my app is crashing, and it appears that its related to memory pressure.
So I looked at this in Instruments. I have Allocations and Memory Monitor in use. Allocations shows a pretty steady 3 to 4 MB Live bytes while I just let my app initialize and come to equilibrium. Overall bytes, however, jumps to over 50 MB. I didn't think much of this until I looked at the Memory Monitor and I see that memory usage goes up and down, causing memory warnings. (It seems strange to me that this doesn't show up on the allocations graph at the same time.)
The app should be at an equilibrium point, but apparently it's not. My question is how can I use instruments to help me understand why memory usages is rising and falling?
Instruments as a tool for debugging is simply excellent. From what I can understand, you have been trying to use the allocations tool, so I'll go over that. Allocations details the number of objects your application allocates during it's execution, along with their in-memory references, locations, even the calling code that allocates said objects. When instruments starts running the allocations tool, your application begins reporting all allocations as blue dots, which pile up higher and higher as your application executes (naturally, as you should be allocating more and more objects). Overall Bytes displays the amount of memory EVERY allocation your app has made added together. I want to stress this for your case: it does not mean your app is currently using 50 mb of memory!, it just means that your app has used 50 mb total. Your app is obviously limited to the amount of memory the device has, and 3-4 mb is not a lot when you consider that the first gen. iPhone had about 128mb, but for more complicated applications, the OS will usually kill off other applications before it kills yours.
As for the other allocation graph with spikes, rather than a continuous line graph, that is to detail the number of allocations going on at that point in time. Usually, the spikes can be ignored, unless there are a lot of large spikes in one small amount of time.
Anyways, to address your specific memory warning problem, it honestly depends how many memory warnings you are receiving, and at what level the warning are at. And as for your leaks, my only word of advice is: Squash them as soon as possible! When you see a leak (a red bar in the leaks tool), click on the bar and find the objects that are being leaked. When you select a leaked object, then select the right sidebar, it will show you the code that is leaking. When you double click on any part of the right sidebar, it'll even open up the specific line and class the leak originated from!
I am Profiling an Application with Instruments. The profiling is done using Allocations Tool in two ways:
By choosing Directly the Allocations when I run the App for Profiling
By Choosing Leaks when I run the App for Profiling.
In both the cases , I had Allocations tool enabled for testing. But surprisingly , I had two different kind of Out put for Allocations at these instances.
Are they supposed to behave differently? or this is a problem with Instruments.
The time I Profile the with Leaks Tool:
In Allocations Graph:
1. I get lot of Peaks in Graph, The Live bytes and overall bytes are same.
2. I get the Black flags (I think it alarms about memory warning) after 1 minutes usage. Then after a set of flags appearing, my App Crashes. (This happens at times, even when directly run the App in Device)
The time I Profile the with Allocation Tool:
In Allocations Graph:
1. I do not get peaks often as it was in the above case. The Live bytes was always way less than Overall bytes.
2. I have used for over 20 minutes and never got Black flags.
One fact I came to know is that, when Live bytes and overall bytes are equal, the NSZombieEnabled could be enabled.
Have any of you ever encountered this problem.
UPDATE 1:
I faced another problem with first case. Whenever I profiled after a short duration (compared to profiling in second case), the app got lots of Black Flags and my App Crashed. (Due to Memory warning)
And when I tried the similar step by step use of Application my Application did not crash and got no flags.
Why this discrepancy?
In the first case, you are only tracking live allocations because the "Leaks" template configures the Allocations instrument that way. In the second, you are tracking both live and deallocated allocations. (As CocoaFu said).
Both are useful, but for slightly different reasons.
Only tracking live allocations (in combination with Heapshot Analysis, typically), is a great way to analyze permanent heap growth in your application. Once you know what is sticking around forever, you can figure out why and see if there are ways to optimize it away.
Tracking all allocations, alive and dead, is a very effective means of tracking allocation bandwidth. You can sort by overall bytes and start with the largest #. Have a look at all the points of allocation (click the little arrow next to the label in the Category of the selected row), and see where all the allocations are coming from.
For example, your graph shows that there are 1.27MB of 14 byte allocations -- 9218 allocations -- over that period of time. All have been free()d [good!], but that still represents a bunch of work to allocate, fill with data (presumably), and free each one of those. It may be a problem, maybe not.
(To put this in perspective, I used this technique to optimize an application. By merely focusing on reducing the # of transient -- short lived -- allocations, I was able to make the primary algorithms of the application 5x faster and reduce memory use by 85%. Turns out the app was copying strings many, many, times.)
Not sure why your app crashed as you described. Since it is a memory warning, you should see what is most frequently allocated.
Keep in mind that if you have zombie detection enabled, that takes a lot of additional memory.
Depending on the way Allocations is instantiated there are different options. Check the options by clicking the "i" symbol in the Allocations tile.
Yes, I find this annoying also.
I want to make sure I'm reading the allocations plug in correctly. I'm testing an iPad app thats receiving memory warnings 1,2 & 3.
I want to know the current used up memory from my app, which I think it has to be the "Live Bytes" column? which marks All Allocations to 2.42 MB which I think its low.
What do the other columns report? #Transitory, Overall Bytes ?
Also if my app uses only 3 MB of memory can it be killed if I get a memory level 3 warning without releasing?
Thank you.
Don't use the Object Allocations instrument for looking at your total memory usage. It does not display the true total memory size of your application, for reasons that I speculate about in my answer here.
Instead, pair Object Allocations with the Memory Monitor instrument, the latter of which will show the true total size of your application. I'm willing to bet that it's way larger than the 2.42 MB you're seeing in Object Allocations (for example, I had an application with 700k of memory usage according to ObjectAlloc, but its actual size was ~25 MB in memory). If you are receiving memory warnings on an iPad, your application is probably chewing up quite a bit of memory.
Object Allocations is handy for telling you what you have resident in memory, but it's not an accurate indicator of the size of those items. It's also a great tool for showing you steady increases in allocated objects by using the heap shot functionality (the "Mark Heap" button on the left-hand side of the instrument).
Your memory usage looks fine. Check to see which app is being sent the memory warnings, it is probably not your app assuming your app is not in the background. The only way you should be getting memory warnings is if the app is in the background and another app needs more memory.
When I was looking at logs I noticed other apps were getting them while my app was running, other apps such as Mail or navigation apps (Navigon) do run in the background and will cause memory pressure. You might get a memory warning but should not be terminated.
For a description of the memory columns see Explanation of Live Bytes & Overall Bytes.
As #Brad points out use the memory monitor tool as well.
I am getting some memory warning in my iOS app so I am running Instruments to see the allocations. Should I look at the * All Allocations * Live Bytes or Overall Bytes?
Someone said the iOS can close my app if I use for 22MB, is that from the Live or Overall bytes section?
Live Bytes is the current usage and is what you are interested in, overall bytes includes all released allocation. The other thing is to look at the graph and look for peaks. As an example I saw a huge peak of about 27MB in an app I was working on, knowing that I was able to reduce peak memory usage to 8MB.
Also watch over time as you exercise your app, it is possible to have substantial memory growth over time that is not leaked, just not not used anymore.
For a description of the memory columns see Explanation of Live Bytes & Overall Bytes.