Deciphering Android Garbage collection (GC) logs

http://infinitesproutingthoughts.wordpress.com/2013/06/21/deciphering-android-garbage-collection-gc-logs/

More often  android adb log dumps below text for GC:

19:30:22.188 26517 26519 D dalvikvm: GC_CONCURRENT freed 82K, 7% free 7524K/8035K, paused 12ms+25ms, total 82ms

GC_CONCURRENT =  all the dalvik VM ‘s thread are being garbage collected.

Freed = 82K,  this cycle of Garbage collection freed 82KilloBytes .

7% free = Free % of  total Java heap(not including native).

7524K/8035K = allocated / total heap.

That is as per  above log: with this GC cycle android VM, freed 82K memory and now total memory foot-print of Java heap is 8035K, out of that 7524K is allocated and rest (7%) is free.

Tip: To find the Java Heap usage for a particular java process(app/service/content provider).i.e(any process forked from Zygote) use below command:

# adb shell ps | grep -i  ”andriod_process_name”

# adb logcat | grep “above_returned_process_id” | grep  ”GC_”

Ex: #adb shell ps | grep -i “com.android.chrome”   (say PID = 2345)

#adb shell ps | grep  2345 | grep  ”GC-”

This should display above explained GC logs, whenever there is GC allocation (GC_cocurrent, GC_alloc, ..etc).

This would be handy and efficient then using “adb shell dumpysys meminfo PID”, as the dumpsys runs in process itself, hence making it bit slow.