When developing Android apps, we might encounter Out of Memory (OOM) errors. A common quick fix is to set the largeHeap flag in our AndroidManifest.xml:
<application
android:largeHeap="true" />But is this the right solution? No! Let’s understand why using largeHeap can actually make our app slower and less efficient.
What Does largeHeap Do?
Setting android:largeHeap="true" gives our app a bigger memory allocation. For example:
- Without largeHeap: our app might get 50MB of memory.
- With largeHeap: our app might get 200MB of memory.
At first, this sounds great—more memory, fewer OOM errors! But there’s a hidden cost.
How Garbage Collection (GC) Works
The Garbage Collector (GC) is responsible for cleaning up unused memory in our app. The more memory our app uses, the longer GC takes to run.
- Small Heap (50MB):
- GC might take 2ms to clean up.
- Large Heap (200MB):
- GC might take 8ms to clean up.
If our app is doing a task that takes 10ms, the total time with GC is:
- Small Heap: 10ms (task) + 2ms (GC) = 12ms (smooth performance)
- Large Heap: 10ms (task) + 8ms (GC) = 18ms (noticeable lag)
Why Large Heap Causes Lag
As our app’s memory usage grows, GC takes longer. This can cause our app to lag or even freeze, especially on lower-end devices.
Example:
- App starts with 50MB → GC is fast.
- App grows to 100MB → GC is slower.
- App grows to 150MB → GC is even slower.
More memory = Slower GC = More lag
Using largeHeap is not a real solution to memory problems. It can make our app slower and less responsive. Instead, focus on efficient memory management and only use largeHeap as a last resort.