CODEWITHSUNDEEP
apache-flexmemory-managementmemory-leaksarraycollection
thameem
thameem

Reputation: 21

Flex consuming huge memory for large data

When flex array collection is handled with large amount of data for example 2,00,000 new referenced objects the memory in flex client browser shoots up 20MB. This excess 20MB is independent of the variables defined in the object. An detailed example is illustrated below.

var list:ArrayCollection =  new  ArrayCollection;
for(var i:int = 0;i<200000;i++)
{
    var obj:Object = new Object;
    list.add(obj);

}

On executing the above code there was 20MB increase in flex client browser memory. For a different scenario i tried adding an action script object into the array collection. The action script object is defined below.

public class Sample
{
    public var id:int;
    public var age:int;
    public Sample()
    {
    }

}

On adding 200000 Sample class into a array collection there was still 20MB memory leak.

var list:ArrayCollection =  new  ArrayCollection;
for(var i:int = 0;i<200000;i++)
{
    var obj:Sample = new Sample;
    obj.id= i;
    onj.age = 20;
    list.add(obj);

}

I even tried adding the Sample Objects into flex arrayList and array but the problem still persists. Can someone explain on where this excess memory is consumed by flex?

Upvotes: 0

Views: 298

Answers (2)

Mike Petty
Mike Petty

Reputation: 949

I have no idea if the OS allocation time is a big deal anymore, we're talking on avg 1.5-2GHz Cpu's - even mobile. But Benoit is on the right track. Large chunks are reserved at a time to mainly avoid heap fragmentation. If memory was requested in only size chunks it needs at a time, along with other IO requests, the system memory would become highly fragmented very quickly. When these fragments are returned to the OS space - unless the memory manager gets a request of the same size or smaller, it cannot reallocate this chunk - thereby making it lost to the visible pool. So to avoid this issue - Flash (and it's memory manager) requests 16Mb at a time.

In your case, it wouldn't matter if you created 1 object or 100,000. You'll still start with a minimum of 16Mb private memory (aka what you see in task manager).

The flash player allocation mechanism is based on the Mozilla MMgc.
You can read about it here: https://developer.mozilla.org/en-US/docs/MMgc

Upvotes: 0

Beno&#238;t Gu&#233;das
Beno&#238;t Gu&#233;das

Reputation: 801

Requesting memory to the OS is time consuming, so Flash player requests large chunks of memory (more than it really needs) in order to minimize the number of those requests.

Upvotes: 1

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