Investigate JavaScript Memory

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Step 1: Identify the crash reason

1. Open the aggregated crash report From the device, download and open the aggregated crash report (ACR).
2. In the ACR file, look for CrashReason:SIGSEGV.
3. Confirm a JavaScript heap overflow To confirm a JavaScript heap memory overflow, check the app logs for HermesGC OOM.

CrashDescriptor:1b26a2ab4b104aa474b84218e69d2780
CrashLang:Native
Process:com.org.keplerApp
LibraryName:keplerscript-runtime-loader-2.so
CrashReason:SIGSEGV

Nov 21 20:10:13.389612 firestick-010bc8cead0041f0 local0.info keplerscript-ru[7087]: 27 I KeplerScript:[Logging.cpp:40] HermesGC OOM: [] reason = Max heap size was exceeded (1 from category: vm_allocate_category), numCollections = 177, heapSize = 205520896, allocated = 201732128, va = 205520896, external = 88.

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Step 2: Identify memory leak scenarios

1. Open Visual Studio (VS) Code.
2. Start the Memory Monitor. Follow the steps in Inspect your app memory consumption.
3. Track the JavaScript heap graph for 200-MB threshold approaches.
4. Record a session to capture crash scenarios. Follow the steps in Record your app memory breakdown.

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Step 3: Capture JavaScript heap snapshots

1. Attach Chrome DevTools Attach Chrome DevTools to your React Native for Vega app. Follow the steps in Start Chrome DevTools.
2. Navigate to the Memory tab and select Heap Snapshot.
3. Click Take snapshot. The following image is an example of a heap snapshot.
4. To download the snapshot onto your host machine, click the down arrow.

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Step 4: Analyze JavaScript heap snapshot

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Analyze with Memlab

1. Install Memlab:
   npm install -g memlab
   
2. Run the analysis:
   memlab find-leaks --baseline <initial-snapshot> --target <post-leak-snapshot> --final <post-clear-snapshot> --trace-all-objects
   
   Memlab compares three heap snapshots:
   • Baseline - The initial state
   • Target - The state after the potential leak
   • Final - The state after cleanup
   --trace-all-objects argument marks all target page objects as potential leaks. memlab find-leaks compares the three heap snapshots and provides a summary in a table format:
3. Find uncleared objects from the table.
4. Check code for deallocating persistent objects.
5. Review retainer traces. Memlab ranks leaked objects on retained sizes. Use retainer traces to locate leaked objects in the object tree.

• Find unreported memory leaks
• Heap analysis
• Memlab CLI commands

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Analyze with Chrome DevTools

1. Open Chrome DevTools and go to the Memory tab.
2. Upload your JavaScript heap snapshot.
3. Analyze the JavaScript heap snapshot using different views:
   • Sort by Shallow Size to find the heaviest objects
   • Sort by Retained Size to identify the most impactful objects

• Object sizes
• View snapshots

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Related topics

• Monitor CPU Usage
• Measure Performance with Chrome DevTools
• 💬 Community: How to check if my app is running out of memory?
• 💬 Community: Log script for bug reports