Slide 1
Slide 1 text
JITIN S HARMA
D E C O D I N G A N D R O I D
R U N T I M E
@_jitinsharma
jitinsharma.in
Slide 2
Slide 2 text
@_jitinsharma / jitinsharma.in
What is Android
-Some Hardware
-Some Linux
-Some C++
-Some Java
Slide 3
Slide 3 text
@_jitinsharma / jitinsharma.in
Slide 4
Slide 4 text
@_jitinsharma / jitinsharma.in
Boot-Up
Slide 5
Slide 5 text
@_jitinsharma / jitinsharma.in
Boot-Up
Hardware Start-Up
02 Software Start-Up
ZYGOTE
03
01
Slide 6
Slide 6 text
@_jitinsharma / jitinsharma.in
Boot-Up
init.rc
AndroidRuntime.cpp Zygote main()
Transition to
Java based execution
Linux Kernel Start
Slide 7
Slide 7 text
@_jitinsharma / jitinsharma.in
Zygote
- Zygote Process acts a base process from which all processes are forked for
subsequent applications.
- This allows Android to run in a Multi-Process environment where all processes
run independent of each other.
- All resources preloaded by Zygote are accessed by subsequent applications
through shared memory.
Slide 8
Slide 8 text
@_jitinsharma / jitinsharma.in
Zygote
System Server
Load core libraries
and resources
Starts Activity Manager
Notification Manager, Bluetooth Service,
Package Manager, Sensor Service…
Slide 9
Slide 9 text
@_jitinsharma / jitinsharma.in
Zygote
Slide 10
Slide 10 text
@_jitinsharma / jitinsharma.in
Phone is ON
Slide 11
Slide 11 text
@_jitinsharma / jitinsharma.in
Building APK
java/kt files .class files .dex
javac
kotlinc
dx/D8
APK
Slide 12
Slide 12 text
@_jitinsharma / jitinsharma.in
Installing Application
Slide 13
Slide 13 text
@_jitinsharma / jitinsharma.in
Manifest Parsing
- All data from AndroidManifest.xml is read and is written to data/system/packages.xml
- This file acts as a global source for all packages and is used by PackageManager API
- This happens only once either when device is booted or an application is being installed.
Slide 14
Slide 14 text
@_jitinsharma / jitinsharma.in
Manifest Parsing
- Identifies various elements within your application
- At the same time manifest performs checks which can cause installation errors if elements are not
defined properly.
Slide 15
Slide 15 text
@_jitinsharma / jitinsharma.in
Code Compilation and Other Stuff
Slide 16
Slide 16 text
@_jitinsharma / jitinsharma.in
Code Compilation and Other Stuff
Dalvik ART
Slide 17
Slide 17 text
@_jitinsharma / jitinsharma.in
dex and Dalvik Era
Android 1.0 - 4.4
(2008-2014)
Slide 18
Slide 18 text
@_jitinsharma / jitinsharma.in
.dex
Dalvik VM
A register based VM optimised for
memory constrained device
.dex -> Dalvik Executable
Slide 19
Slide 19 text
@_jitinsharma / jitinsharma.in
Stack Machines
value1
value2
value3
value4
value1 value2
operation
pop pop
value5
value3
value4
push
Slide 20
Slide 20 text
@_jitinsharma / jitinsharma.in
Stack Machines Register Machines
value1
value2
value3
value4
value1 value2
operation
pop pop
value5
value3
value4
push
addr1 value1
operation
addr2 value2
addr3 value3
Slide 21
Slide 21 text
@_jitinsharma / jitinsharma.in
Stack Machines Register Machines
value1
value2
value3
value4
value1 value2
operation
pop pop
value5
value3
value4
push
addr1 value1
operation
addr2 value2
addr3 value3
ARM Optimized
Slide 22
Slide 22 text
@_jitinsharma / jitinsharma.in
dex
- Uses 16 bit instruction format.
- Bytecode tends to be larger due to register based architecture for storing addresses
Slide 23
Slide 23 text
@_jitinsharma / jitinsharma.in
dex
- Uses 16 bit instruction format.
- Bytecode tends to be larger due to register based architecture for storing addresses
‣header
‣string_ids
‣type_ids
‣proto_ids
‣field_ids
‣method_ids
‣class_defs
‣call_site_ids
‣method_handles
‣data
‣link_data
Slide 24
Slide 24 text
@_jitinsharma / jitinsharma.in
dex
- Uses 16 bit instruction format.
- Bytecode tends to be larger due to register based architecture for storing addresses
‣header
‣string_ids
‣type_ids
‣proto_ids
‣field_ids
‣method_ids
‣class_defs
‣call_site_ids
‣method_handles
‣data
‣link_data
Contains verification
signatures
Slide 25
Slide 25 text
@_jitinsharma / jitinsharma.in
dex
Slide 26
Slide 26 text
@_jitinsharma / jitinsharma.in
dex
Slide 27
Slide 27 text
@_jitinsharma / jitinsharma.in
public class Data {
int id;
String name = "";
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Slide 28
Slide 28 text
@_jitinsharma / jitinsharma.in
public int getId() {
return id;
}
.METHOD getId : int
.MODIFIERS public
.REGISTERS 2
.CODE
iget v0, v1 field@8046
return v0
.METHOD setName : void
.PARAM java.lang.String
.MODIFIERS public
.REGISTERS 2
.CODE
iput-object v1, v0 field@8047
return-void
public void setName(String name) {
this.name = name;
}
Slide 29
Slide 29 text
@_jitinsharma / jitinsharma.in
private fun forEachTest(): Int {
var sum = 0
(0..50).forEach {
sum += it
}
return sum
}
private fun forTest(): Int {
var sum = 0
for (i in 0 until 50) {
sum += i
}
return sum
}
VS
Slide 30
Slide 30 text
@_jitinsharma / jitinsharma.in
private fun forTest(): Int {
var sum = 0
for (i in 0 until 50) {
sum += i
}
return sum
}
.METHOD forTest : int
.MODIFIERS private final
.REGISTERS 4
.CODE
const/4 v0, #0
const/4 v1, #0
const/16 v2, #50
if-ge v1, v2, 6
add-int/2addr v1, v0
add-int/lit8 v1, v1, #1
goto -7
return v0
Slide 31
Slide 31 text
@_jitinsharma / jitinsharma.in
private fun forEachTest(): Int {
var sum = 0
(0..50).forEach {
sum += it
}
return sum
}
.METHOD forEachTest : int
.MODIFIERS private final
.REGISTERS 8
.CODE
const/4 v0, #0
new-instance v1, type@2439
const/4 v2, #0
const/16 v3, #50
invoke-direct {v1, v2, v3}, meth@20280
check-cast v1, type@1851
move v3, v2
invoke-interface {v1}, meth@15176
move-result-object v4
invoke-interface {v4}, meth@15640
move-result v5
if-eqz v5, 13
move-object v5, v4
check-cast v5, type@2142
invoke-virtual {v5}, meth@18564
move-result v5
move v6, v5
add-int/2addr v6, v0
goto -16
return v0
Slide 32
Slide 32 text
@_jitinsharma / jitinsharma.in
A.class
B.class
Z.class
classes.dex
Slide 33
Slide 33 text
@_jitinsharma / jitinsharma.in
A.class
B.class
Z.class
classes.dex
- Reduction in bytecode size during conversion.
- Duplicate constants from class files are converted to a single one.
- Each method needs have a reference which is limited by dex instruction format
of 16 bits, hence total method references which a single dex file can hold is
65,536 (2^16)
Slide 34
Slide 34 text
@_jitinsharma / jitinsharma.in
dex++
Slide 35
Slide 35 text
@_jitinsharma / jitinsharma.in
Multidexing
classes.dex
java/kt
classes2.dex classesN.dex
…
Slide 36
Slide 36 text
@_jitinsharma / jitinsharma.in
Installation
data/dalvik-cache
data/data/com.example.myapplication
Slide 37
Slide 37 text
@_jitinsharma / jitinsharma.in
dexopt
-Verification and Optimization of contents of .dex file
-Result differ from device to device.
-Starts a small version of VM to optimize dex files.
-Contents of system/framework/ can be used to optimize dex files outside
Android OS.
-Code is optimized for runtime not memory.
Slide 38
Slide 38 text
@_jitinsharma / jitinsharma.in
classes.dex
My Application
Zygote
Process
Slide 39
Slide 39 text
@_jitinsharma / jitinsharma.in
Multidex.install(this)
classes.dex classes2.dex classes3.dex ….
System Application
classesN.dex
Inject values
into ClassLoader
Slide 40
Slide 40 text
@_jitinsharma / jitinsharma.in
Multidex.install(this)
classes.dex classes2.dex classes3.dex ….
System Application
Must have Application class
classesN.dex
Inject values
into ClassLoader
Slide 41
Slide 41 text
@_jitinsharma / jitinsharma.in
Multidex.install(this)
classes.dex classes2.dex classes3.dex ….
System Application
Must have Application class
Library dependencies
classesN.dex
Inject values
into ClassLoader
Slide 42
Slide 42 text
@_jitinsharma / jitinsharma.in
Multidex.install(this)
classes.dex classes2.dex classes3.dex ….
System Application
Must have Application class
Library dependencies
(multiDexKeepFile)
classesN.dex
Inject values
into ClassLoader
Slide 43
Slide 43 text
@_jitinsharma / jitinsharma.in
DexClassLoader
DexClassLoader dexClassLoader = new DexClassLoader(dexFile.getAbsolutePath(),
getCodeCacheDir().getAbsolutePath(), null, context.getClassLoader());
Slide 44
Slide 44 text
@_jitinsharma / jitinsharma.in
DexClassLoader
DexClassLoader dexClassLoader = new DexClassLoader(dexFile.getAbsolutePath(),
getCodeCacheDir().getAbsolutePath(), null, context.getClassLoader());
Network
Slide 45
Slide 45 text
@_jitinsharma / jitinsharma.in
DexClassLoader
DexClassLoader dexClassLoader = new DexClassLoader(dexFile.getAbsolutePath(),
getCodeCacheDir().getAbsolutePath(), null, context.getClassLoader());
Class> dynamicClass = dexClassLoader.loadClass("com.example.myapplication.runtime");
Method dynamicMethod = dynamicClass.getDeclaredMethod("executeDataLoad", Integer.class, Integer.class);
Integer value = (Integer) dynamicMethod.invoke(dynamicClass.newInstance(), 1, 2);
Network
Slide 46
Slide 46 text
@_jitinsharma / jitinsharma.in
DexClassLoader
DexClassLoader dexClassLoader = new DexClassLoader(dexFile.getAbsolutePath(),
getCodeCacheDir().getAbsolutePath(), null, context.getClassLoader());
Class> dynamicClass = dexClassLoader.loadClass("com.example.myapplication.runtime");
Method dynamicMethod = dynamicClass.getDeclaredMethod("executeDataLoad", Integer.class, Integer.class);
Integer value = (Integer) dynamicMethod.invoke(dynamicClass.newInstance(), 1, 2);
Network
public Integer executeDataLoad(Integer value1, Integer value2) {
//
return result;
}
Slide 47
Slide 47 text
@_jitinsharma / jitinsharma.in
DexClassLoader
DexClassLoader dexClassLoader = new DexClassLoader(dexFile.getAbsolutePath(),
getCodeCacheDir().getAbsolutePath(), null, context.getClassLoader());
Class> dynamicClass = dexClassLoader.loadClass("com.example.myapplication.runtime");
Method dynamicMethod = dynamicClass.getDeclaredMethod("executeDataLoad", Integer.class, Integer.class);
Integer value = (Integer) dynamicMethod.invoke(dynamicClass.newInstance(), 1, 2);
Network
public Integer executeDataLoad(Integer value1, Integer value2) {
//
return result;
}
Slide 48
Slide 48 text
@_jitinsharma / jitinsharma.in
JIT
Slide 49
Slide 49 text
@_jitinsharma / jitinsharma.in
JIT
private void handleIntent() {
...
public RequestQueue getRequestQueue() {
if (requestQueue == null) {
requestQueue = Volley.newRequestQueue(this);
}
return requestQueue;
}
for (String s : networkRequestMap.keySet()) {
if (BuildConfig.DEBUG) {
//
Slide 50
Slide 50 text
@_jitinsharma / jitinsharma.in
Tracing and Profiling
Low Memory
Optimized
(100K/200K)
Faster results
Google I/O 2010
Slide 51
Slide 51 text
@_jitinsharma / jitinsharma.in
Shortcomings of Dalvik
Time
Slide 52
Slide 52 text
@_jitinsharma / jitinsharma.in
ART (Android Runtime)
Android 5.0 - present
(2014-present)
Slide 53
Slide 53 text
@_jitinsharma / jitinsharma.in
Embracing the GBs…
Slide 54
Slide 54 text
@_jitinsharma / jitinsharma.in
Slide 55
Slide 55 text
@_jitinsharma / jitinsharma.in
Slide 56
Slide 56 text
@_jitinsharma / jitinsharma.in
Embracing the GBs…
Slide 57
Slide 57 text
@_jitinsharma / jitinsharma.in
Revamped GC
-ART keeps track of application going in non-UI state.
-Seperate types of GC for low memory and non-low memory devices.
-GC pauses reduced from 2 to 1.
-Larger objects like bitmap have seperate heap for faster allocation.
-Young Objects are moved to stack for faster reclamation of memory.
Slide 58
Slide 58 text
@_jitinsharma / jitinsharma.in
Dalvik
GC GC GC
1MB 3MB 5MB
Slide 59
Slide 59 text
@_jitinsharma / jitinsharma.in
ART
GC GC GC
1MB 3MB 5MB
Slide 60
Slide 60 text
@_jitinsharma / jitinsharma.in
ART
GC GC GC
1MB 3MB 5MB
9MB
Heap
Compaction
Slide 61
Slide 61 text
@_jitinsharma / jitinsharma.in
AOT Compilation
classes.dex
classes2.dex
classesN.dex
.oat
dex2oat
- AOT works on principle of compile once and then run.
- Compilation takes significant time and memory since whole bytecode is converted to
machine code at installation.
- AOT compilers do not benefit from profile guided compilation which JIT compilers have
instead use a restrictive approach to do compilation.
Android
Runtime
VM
Slide 62
Slide 62 text
@_jitinsharma / jitinsharma.in
.oat
header
instruction set
dex file count
dex2oat cmd line
code
data/app/
Slide 63
Slide 63 text
@_jitinsharma / jitinsharma.in
DEX CODE:
0x0000: 5210 e10f | iget v0, v1, I com.example.myapplication.Data.id // field@4065
0x0002: 0f00 | return v0
public int getId() {
return id;
}
Java
Slide 64
Slide 64 text
@_jitinsharma / jitinsharma.in
CODE:
(code_offset=0x00d6a3fc size_offset=0x00d6a3f8 size=68)...
0x00d6a3fc: 4885842400E0FFFF testq rax, [rsp + -8192]
suspend point dex PC: 0x0000
GC map objects: v1 ([sp + #40])
0x00d6a404: 4883EC18 subq rsp, 24
0x00d6a408: 48893C24 movq [rsp], rdi
0x00d6a40c: 89742428 mov [rsp + 40], esi
0x00d6a410: 6566833C250000000000 cmpw gs:[0], 0 ; state_and_flags
0x00d6a41a: 0F8516000000 jnz/ne +22 (0x00d6a436)
0x00d6a420: 8B442428 mov eax, [rsp + 40]
0x00d6a424: 8500 test eax, [rax]
suspend point dex PC: 0x0000
GC map objects: v1 ([sp + #40])
0x00d6a426: 8B480C mov ecx, [rax + 12]
suspend point dex PC: 0x0000
GC map objects: v1 ([sp + #40])
0x00d6a429: 894C2410 mov [rsp + 16], ecx
0x00d6a42d: 8B442410 mov eax, [rsp + 16]
0x00d6a431: 4883C418 addq rsp, 24
0x00d6a435: C3 ret
0x00d6a436: 65FF142538040000 call gs:[1080] ; pTestSuspend
……..
Slide 65
Slide 65 text
@_jitinsharma / jitinsharma.in
Problems with AOT compilation
Slide 66
Slide 66 text
@_jitinsharma / jitinsharma.in
Slide 67
Slide 67 text
@_jitinsharma / jitinsharma.in
JIT/AOT Hybrid
‣System boot after OS update will no longer optimise the app, a job solely performed by JIT.
‣dex2oat is still used for .oat creation but it uses profile data generated by JIT to do so.
‣Code may be executed by directed .dex interpretation or JIT cache or AOT compiled.
‣At any time JIT compiled data will be more efficient because of availability of better environment
data than AOT compiled code, and the same is preferred if both are present.
Slide 68
Slide 68 text
@_jitinsharma / jitinsharma.in
DEX CODE:
0x0000: 5210 e10f | iget v0, v1, I com.example.myapplication.Data.id // field@4065
0x0002: 0f00 | return v0
public int getId() {
return id;
}
Java
CODE:
(code_offset=0x00000000 size_offset=0x00aea110 size=0)
NO CODE!
Slide 69
Slide 69 text
@_jitinsharma / jitinsharma.in
Cloud Profiles
Slide 70
Slide 70 text
@_jitinsharma / jitinsharma.in
Third party frameworks
Slide 71
Slide 71 text
@_jitinsharma / jitinsharma.in
Future
Slide 72
Slide 72 text
@_jitinsharma / jitinsharma.in
Future
A.I
Slide 73
Slide 73 text
@_jitinsharma / jitinsharma.in
Thanks