memory_management_for_android_apps.pdf

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1、MemoryManagementforAndroidAppsPatrickDubroy(dubroy.com·@dubroy)May11,2011192MBRAM31GBRAM4Xoom1280x800G1320x48056SoftwareWorkexpandstofillthetimeavailable.memory7Overview•ChangesinGingerbreadandHoneycomb–heapsize–GC–bitmaps•Understandingheapusage–logs–memoryleaks–EclipseMemo

2、ryAnalyzer(MAT)8Expectations•Android•Dalvikheap•Garbagecollection•OutOfMemoryError9HeapSize•Heapsizelimits–G1:16MB–Droid:24MB–NexusOne:32MB–Xoom:48MB•ActivityManager.getMemoryClass()10LargeHeaps•Honeycombadds“largeHeap”optioninAndroidManifest.xml:–Degradesperformance!Useon

3、lyifyouunderstandwhyyouneedit.ActivityManager.getLargeMemoryClass()11GarbageCollectionGCRoots12GarbageCollectionGCRoots13GarbageCollectionGCRoots14GarbageCollectionGCRoots15GarbageCollect

4、ion•Biggerheaps=longerpauses?•Pre-GingerbreadGC:–Stop-the-world–Fullheapcollection–Pausetimesoften>100ms•Gingerbreadandbeyond:–Concurrent(mostly)–Partialcollections–Pausetimesusually<5ms16BitmapsOldway(pre-Honeycomb):–freedviarecycle()orfinalizer–hardtodebug–full,stop-the-w

5、orldGCsManagedNative17BitmapsOldway(pre-Honeycomb):–freedviarecycle()orfinalizer–hardtodebug–full,stop-the-worldGCsManagedNativeNewway:–freedsynchronouslybyGC–easiertodebug–concurrent&partialGCs18Overview•ChangesinGingerbreadandHoneycomb–heapsize–GC–bitmaps•Understandinghea

6、pusage–logs–memoryleaks–EclipseMemoryAnalyzer(MAT)19Overview•ChangesinGingerbreadandHoneycomb–heapsize–GC–bitmaps•Understandingheapusage–logs–memoryleaks–EclipseMemoryAnalyzer(MAT)20InterpretingLogMessagesD/dalvikvm(9050):GC_CONCURRENTfreed2049K,65%free3571K/9991K,external

7、4703K/5261K,paused2ms+2ms21InterpretingLogMessagesD/dalvikvm(9050):GC_CONCURRENTfreed2049K,65%free3571K/9991K,external4703K/5261K,paused2ms+2ms•ReasonforGC–GC_CONCURRENT–GC_FOR_MALLOC–GC_EXTERNAL_ALLOC–GC_HPROF_DUMP_HEAP–GC_EXPLICIT22InterpretingLogMessagesD/dalvikvm(9050)

8、:GC_CONCURRENTfreed2049K,65%free3571K/9991K,external4703K/5261K,paused2ms+2ms•ReasonforGC