2008kandroid-2

Android Kernel Issues

Android Kernel Issues

2008 Korea Android(www.kandroid.org)

CONTENTS

PART 1. Overview

PART 2. OpenBinder

PART 3. EABI

PART 4. Low Memory Killer

- CTO - S/W Lab - Lim,GeunSik ([email protected])

본 행사는 구글 안드로이드와 같은 오픈 모바일 플랫폼을 구현하기 위해 필요한 여러 기술과 적용 방안에 대해 알아보는 자리입니다.

실제 경험과 Know-how를 중심으로 구성된 본 행사는 모바일 비즈니스의 새로운 사업 모델을 창출하는 계기가 될 것입니다.

Overview1.

PART 1. Overview

PART 2. OpenBinder

PART 3. EABI


4/34software stack for mobile devices (Android)

2008 Korea Android

Part 1 License Related Android & OpenSource

’

Google (Skia)SGL

MITExpat

GPL2DBUS

GPL+BSDKHTML

LGPLKJS

LGPLWebCore

BSD (including LGPL)

Webkit

BSD NetBSD C Library

SGI OpenGL (BSD/MPL)

OpenGL

LGPLSDL

Apacheant

PythonPython

GPL2SQLite

GPL2OpenBinder (Core)

Google (Apache)

Dalvik (JVM)

GPL2QEMU Accelerator

GPLQEMU

GPLYAFFS2

GPL2Linux Kernel

•What is Android’s License? •Currently, Android Platform is open source completely. The Android mobile OS will be released under Apache License. This means that anyone can customize the android platform and then keep it proprietary.


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Part 1 Android Kernel Features

△init ramfs source ( To run /init - Exectuable Liking Format )

△Panic Timeout ( To manage timout value when panic)

△Goldfish (Virtual Machine for QEMU based Emulator )Emulator

△Android Power Driver( for power management of goldfish )

/dev/android_power

△Android RAM Buffer Console ( for goldfish's audio )

△Android USB Gadget ( Gadget based Android USB Driver)

/dev/usb

△Android Log Driver (Android Log Subsystem to display log messages like logcat)

/dev/log/{main:log:event}

Android

△( To Manage process When Memory is low)Misc

△Touch-Screen Device drivers

O( For IPC between processes ) /dev/binder (251 ~ 253)

OFrame Buffer (Device Driver) /dev/fb0

O( Embedded ABI )


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Part 1 What is Cross Compiler to build Kernel?

Select Cross Compiler for ARM v6

Sourcery G++ Lite Edition (CodeSourcery's version of the GNU Toolchain)

arm-2007q3-53-arm-none-eabi-i686-pc-linux-gnu.tar.bz2

export PATH=$PATH :<cross_compiler_install_path>/bin/

Android Kernel: http://android.googlecode.com/files/linux-2.6.23-android-m3-rc20.tar.gz

We need opensource for toolchain like Kernel, gcc, glibc, bintuils

http://www.codesourcery.com/gnu_toolchains/arm/download.html

Download the ARM 2007q3 Release

Select "ARM EABI, IA32 GNU /Linux Option (Radio Box)" and Download

- Target Platform: ARM EABI

- Host Platform: IA32 GNU/Linux

- Source Code: Unchecked

Default Floating Point : Soft-Float

If you are want to compile hard-float option to enable VFP Instruciton,

Use -mfpu=vfp -mfloat-abit=softfp

How to get CodeSource Toolchain


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Part 1 How to build Kernel Source for Android Platform

Get default .config file from rootFS of anroid emulator.

fc6#> tar xzf linux-2.6.18-arm1136jf-s.armadillo-500.android.tar.gz fc6#> cd linux-2.6.18-arm1136jf-s.armadillo-500fc6#> cp ./arch/arm/configs/goldfish_defconfig ./.config (GoldFish Config File)fc6#> make ARCH=arm CROSS_COMPILE=arm_none-linux-gnueabi- menuconfig fc6#> make ARCH=arm CROSS_COMPILE=arm_none-linux-gnueabi- zImagefc6#> make ARCH=arm CROSS_COMPILE=arm_none-linux-gnueabi- modulesfc6#> make ARCH=arm CROSS_COMPILE=arm_none-linux-gnueabi- modules_installfc6#> cp ./arch/arm/boot/zImage /tftpboot/fc6#> cp –rf /lib/modules/ linux-2.6.18-arm1136jf-s.armadillo-500 /tftpboot/target/lib/modules/

Build 2.6 Kernel Source

fc6#> <android_sdk_install_path>/tools/emulator –console –debug-kernel –kernel kernel-qemufc6#> adb pull /proc/config.gz ./fc6#> gunzip config.gzfc6#> vi ./.config

OpenBinder2.

PART 1. Overview

PART 2. OpenBinder

PART 3. EABI



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Part 2 What is OpenBinder?

OpenBinder?

•A complete open-source solution supporting new kinds of component-based system-level design.

• Resource management between processes.• Binder is system oriented rather than application oriented.• Support a new kind of component-based system-level development.• Component/object representations of various basic system services.• Binder itself does not impose a particular threading model.• The Binder has been used to implement a wide variety of commercial-quality system-level services.

Openbiner’s History

OHAOHA

1998 Binder is developed by BeOS.2001 Palm Company acquired BeOS.2001 Palm’s Micro Kernel is consist of Binder.2004 netBSD Cobalt Kernel http://www.netbsd.org/ports/cobalt/2005 Contributed by Palm(OHA Member) , 2005 Google used Openbinder for android. (Not Opensource : graphics , user interface , multimedia ramework)2007 Current BeOS (http://www.beosmax.org)


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Part 2 Why OpenBinder?

ardware Scalability

ystem Customization

obust Applications

These platforms were designed to run on small handheld or dedicated devices,

• The mobile device world tends to have a much broader range of hardware capabilities than is found on desktops. size and battery life

• ability to run on anything from a 50MHz ARM 7 CPU (without memory protection) up to a 400MHz ARM 9 CPU and beyond. burden on system software

• Both hardware manufacturers and phone carriers want to deeply customize their behavior.

• it much easier to support this kind of customizability in a manageable way.

• Usage of the screen can become a significant problem for more complicated applications, such as web browsers.

• Binder helps address this issue by making it easy for one application to sandbox other parts of itself.


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Part 2 How to Use OpenBinder Driver in Kernel

make menuconfig & Device Node & Binding Example

…………………… Upper Omission…………………….VFS: Mounted root (ext3 filesystem).Freeing init memory: 120Kinit: HOW ARE YOU GENTLEMENinit: reading config fileinit: device initinit: mtd partition -1, init: mtd partition 0, "nor.bootlinit: mtd partition 1, "nor.kerneinit: mtd partition 2, "nor.userlinit: mtd partition 3, "nor.confiinit: mtd partition 4, "nand.ipl"init: mtd partition 5, "nand.kerninit: mtd partition 6, "nand.userinit: mtd partition 7, "nand.freesh: can't access tty; job control turned off# binder_open(c3be4438 c053b500) (pid 1593) got c2c81000binder_open(c3be4438 c35291e0) (pid 1605) got c19b8000binder_open(c3be4438 c06a35a0) (pid 1640) got c0cff000binder_open(c3be4438 c06a3c80) (pid 1642) got c0db9000binder_open(c3be4438 c3519e40) (pid 1601) got c099f000binder_open(c3be4438 c09f4ee0) (pid 1654) got c0a9b000…………………… Below Omission …………………

•OpenBinder의 자체적인 통신은 커널 Device Driver으로 통신할 수 있는 주어진 핸들에서 ioctl를 사용하여 수행.

/• Android 의 Process(Thread) 생성시마다 binder라는 IPC Mechanism이 부착됨.


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Part 2 Map info of Google Map Process

dd

•

•System for sending messages between applications.(Systemwide message-bus service) http://www.freedesktop.org/software/dbus/

•Don't worry about processes or IPC Because of distributed architecture.•Provides resource management between processes.•Handle on an object in another proces.•Powerful facilities for doing multithreaded programming with the Binder.

http://www.open-binder.org

<ps information on android platform>root 1657 1 100512 24852 ffffffff afe0d204 S /system/bin/runtimebluetooth 1658 1 1224 776 c00a34e8 afe0d07c S /system/bin/dbus-daemon

<./dbus-daemon/bus/>activation.c, bus.c, config-loader-expat.cconfig-parser.c, connection.c, desktop-file.c, dispatch.c, driver.c, expirelist.c, bus/policy.c, services.c, signals.c


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Part 2 How to combine Openbinder and Udev in rootFS

Priority of Created Thread in Android Kernel

target#> cd /etc/udev/rules.d/target#> vi binderdev.rules

KERNEL=="binder*", NAME="%k", MODE="0666"target#> vi /etc/autobinder.sh

# you almost certainly want to run this with sudodepmodmodprobe binderdevecho lsmod | grep binderlsmod | grep binderls /dev/binder

•

target#> insmod binderdev.kotarget#> lsmod

Module Size Used by Not taintedbinderdev 63152 0 - Live 0xbf000000

target#> mknod /dev/binder c 253 0target#> /bin/chmod -R a+rw /dev/binder


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Part 2 OpenBinderOpenBinder Ver 0.8 Package

make_strings [OPTIONS] strings.xml,

pidgen [flags] foo.idl Google Web APIs (http://api.google.com/search/beta2 SOAP RPC Router )tools

Binder Process(loop) , Custom Package Manager , Custom Package Managerservers

Script Collection ( boot, process_wrapper , setup_env )scripts

Sample Code ( Binder Component , Binder Based System Service , Service Process , Binder Shell Script)samples

Core Openbinder system (Openbinder Kernel Module)

binder lib(arm,generic,x86) , binder_component_glue lib , binder_glue lib , dmproviderlib(Schema)

libraries

Interface Definition Language ( app , package , services, storage, support)interfaces

Header files ( app, dmprovider, pacakage ,pacakge_p , services , storage , support support_p , xml , xml_p )headers

Quick Start Manual (doxgen)docs

Kits, services (MemoryDealer) , tools (BinderShell , commands)components

3way, bomber , bshcommands

Makefiles collection (ex:All binder libraries , PackageNamespace [org.openbinder.tools], PackageLeaf [BinderShell])

build_system

DescriptionName

http://www.mozilla.org/MPL/

※ OpenBinder는 OS 설계를 위한 객체 지향적 접근 방식을 시도한 기존과는 다른 새로운 방식의 접근 방식으로, 전통적인 Kernel에 의해 구성되는 객체 지향적 운영체제 환경을 제공함.

※ 시스템의 가장 큰 힘은 다중 프로세스들로 작업이 수행될 때이며, Kernel Module로 Build되는 OpenBinder는 프로세스들간의 상호작용 및 오브젝트 참조를 효율적으로 관리하기 위하여 Binder에 의해 사용되는 특별한 IPC 메커니즘을 이용.


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Part 2 OpenBinder Contributors

Main Role of Conrtibutor

[email protected] Tsai

Package manager, settings catalog, Binder Shell, data model, port to Linux

[email protected] Parks

General design, XML parser, BBinder, marshalling and [email protected] Onorato

SBuffer, SBufferChain, [email protected] Moon

Initial design and implementation. especially of Ibinder / BBinder, the Binder kernel module , gehnaphores(lightweight locks), SAtom, SHandler

[email protected] Hoffman

Binder kernel module (versions 2 and 4)[email protected] H j& oslash

General design, support classes, SValue, SLocker and SAtomdebugging , data model, documentation

[email protected] Hackborn

Marshalling and pidgen, [email protected] Dance

Linux Binder module, IMemory, Memory [email protected] Boudreau

Port of user-space code to [email protected]

Kenneth Albanowski

RoleE-mailAuthor(Contributor)


2008 Korea Android

Part 2 Core OpenBinder System

File List

i/o buffer Structure 45Iobuffer.h

Init, Read Raw, Write Raw, Drain, Remaining, Consumed, Remainder112Iobuffer.c

binder_transaction Structure128binder.transaction.h

Transaction Init , Transaction Dtor , Transacton Debug Dump, Transaction Create, Transaction Destroy, Transaction ReleaseTarget

542binder_transaction.c

binder_thread Structure154binder-thread.h

Thread Cleanup , Thread WaitForReply , Thread WaitForRequest, Thread Return Transaction, Thread init , Thread GloablCount , Thread Released , Thread Die , Thread AttachProcess, Thread Wakeup , Thread Sync, Thread Write, Thread Read , Etc

1,576binder_thread.c

Descriptor Sturcture , Reverse_mapping Structure, Local_mapping Structure,

Range_map Structure, Death_notification Structure, binder_proc Structure227binder_proc.h

Process init , Process Spawn Looper , Process wakeup timer , process idle timer , set_thread_priority , Process Stop , Process Destroy , Process Die , Process AddThread , Process RemoteThread , Process Transact , Process FreeBuffter , Etc

2,216binder_proc.c

Binder node’s Structure71binder_node.h

Node Global, Node Init , Node AcquireHome, Node Send , Node Destroy141binder_node.c

cmpxchg32 , compare_and_swap32341binder-defs.h

open, mmap , release , ioctl, unlocked ioctl692binder.c

DescriptionLineFile Name

http://www.gnu.org/copyleft/gpl.html/


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Part 2 Thread’s Priority binding to the OpenBinder

Priority of Created Thread in Android Kernel

static void (pid_t thread, int priority){// Android Kernel’s Scheduling is Dynamic Priority(=Normal Priority ) to schedule between threads.int nice;// The following must match SysThreadChangePriority in libbinder.if(priority >= 80) Worse Priority or low priority ( map 80..100 to 0..19)

{ nice = priority - 80;if(nice > 19)nice = 19;

}else Better priority or High Priority ( map 0..79 to -20..-1)

{ nice = priority-3 - 80; nice /= 4;

}//printk(“*invain’s DEBUG: set_thread_priority tid %d pri %d == nice %d₩n", thread, priority, nice);set_user_nice(find_task_by_pid(thread), nice);}

•

•

•We Implement Userspace Realtime Application with Locked Mutex Method (FUTEX)

(Ex: Priority Queuing , Priority Inheritance , Robust Mutex )

’’

EABI (Embedded Application Binary Interface)3.

PART 1. Overview

PART 2. OpenBinder

PART 3. EABI



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Part 3 What is EABI?EABI(Embedded Application Binary Interface)

•It sets the standard for the interoperation between relocated files, as well as executable files, for embedded architectures.•the standard makes it possible to combine object files built using different toolchains if both their compilers use EABI. •GCC : CS-2005Q3 release is a modified version of gcc-3.4.4 from gcc-4.1.0 •The commercial ARM RealView C/C++ compiler was the first to support EABI (GCC4.1)•Kernel: EABI is supported in the ARM Linux kernel from version 2.6.16.•Glibc : Earlier glibcs (2.3.3) support EABI userspace but had old-style syscalls to work with older kernels (2.6.8-2.6.15).

Compatability with ARMv5t processors and above (for GCC 4.2).5

More efficient syscall convention. ( Ref1)4

More compatibility with various development tools.3

Better structure packing capabilities.2

Ability to mix soft and hardfloat code. (GCC 4.2: --with-fpu=vfp --with-float=softfp)1

FeaturesNo

- http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ihi0036a/ARM Information Center

Ref 1) Experience showed that those syscall wrappers can not cover all the needed ABI mismatch since some of them are simply hidden from the C library, especially with specialized applications like iptables for example.

The effective features for arm-linux users with the use of EABI are


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Part 3 Extending the ARM Processor Portfolio

•Continued licensing of both mature and new technology

•Cortex-A9 Ecosystem EDA, OS and Software companies supporting Cortex-A9


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Part 3 Arch & CPU information of GCC about android

…………………………… Upper Omission …………………………{"armv4t", arm7tdmi, "4T", FL_CO_PROC | FL_FOR_ARCH4T, NULL},{"armv5", arm10tdmi, "5", FL_CO_PROC | FL_FOR_ARCH5, NULL},{"armv5t", arm10tdmi, "5T", FL_CO_PROC | FL_FOR_ARCH5T, NULL},{"armv5e", arm1026ejs, "5E", FL_CO_PROC | FL_FOR_ARCH5E, NULL},{"armv5te", arm1026ejs, "5TE", FL_CO_PROC | FL_FOR_ARCH5TE, NULL},{"armv6", arm1136js, "6", FL_CO_PROC | FL_FOR_ARCH6, NULL},{"armv6j", arm1136js, "6J", FL_CO_PROC | FL_FOR_ARCH6J, NULL},{"armv6k", mpcore, "6K", FL_CO_PROC | FL_FOR_ARCH6K, NULL},{"armv6z", arm1176jzs, "6Z", FL_CO_PROC | FL_FOR_ARCH6Z, NULL},{"armv6zk", arm1176jzs, "6ZK", FL_CO_PROC | FL_FOR_ARCH6ZK, NULL},{"armv6t2", arm1156t2s, "6T2", FL_CO_PROC | FL_FOR_ARCH6T2, NULL},{"armv7", cortexa8, "7", FL_CO_PROC | FL_FOR_ARCH7, NULL},{"armv7-a", cortexa8, "7A", FL_CO_PROC | FL_FOR_ARCH7A, NULL},{"armv7-r", cortexr4, "7R", FL_CO_PROC | FL_FOR_ARCH7R, NULL},{"armv7-m", cortexm3, "7M", FL_CO_PROC | FL_FOR_ARCH7M, NULL},{"ep9312", ep9312, "4T", FL_LDSCHED | FL_CIRRUS | FL_FOR_ARCH4, NULL},{"iwmmxt", iwmmxt, "5TE", FL_LDSCHED | FL_STRONG | FL_FOR_ARCH5TE | FL_XSCALE | FL_IWMMXT , NULL},{NULL, arm_none, NULL, 0 , NULL}

};

…………………………… Upper Omission …………………………

{"arm10t", ARM_ARCH_V5T, FPU_ARCH_VFP_V1, NULL},{"arm10tdmi", ARM_ARCH_V5T, FPU_ARCH_VFP_V1, NULL},{"arm10e", ARM_ARCH_V5TE, FPU_ARCH_VFP_V2, NULL},{"arm1020", ARM_ARCH_V5TE, FPU_ARCH_VFP_V2, "ARM1020E"},

•http://gcc.gnu.org/svn/gcc/branches/gcc-4_3-branch/gcc/config/arm/arm.c

•http://sourceware.org/cgi-bin/cvsweb.cgi/src/gas/config/tc-arm.c?cvsroot=src


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The common gcc command options that are available for EABI are

Part 3 Cross Compiler for EABI

ARM syscall entry convention

EABI user space binaries put the syscall number into r7 and use swi 0 to call the kernel. Syscall register arguments are also expected to have EABI arrangements , that is, 64-bit arguments should be put in a pair of registers from an even register number.Example ARM sycall entry convention with long ftruncate64 (unsigned int fd, loff_tlength.

Follow the EABI requirement of always creating a frame pointer whenever a stack frame is allocated. This option is enabled by default and can be disabled with -mno-linked-fp.

-mlinked-fp

Generate position-independent EABI code.-mlibrary-pic

Specify both -mcall-sysv and -mno-eabi options.-mcall-sysv-noeabi

Specify both -mcall-sysv and -meabi options.-mcall-sysv-eabi

Generate code for the given ABI.-mabi=eabi

DescriptionGCC Option


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• put fd into r0• put length into r1-r2• use “swi #(0x900000 + 194)” to call the kernel

EABI

Compatibility

Part 3 Legacy ABI vs. EABI

• put fd into r0• put length into r2-r3 (skipping over r1)• put 194 into r7• use “swi 0" to call the kernel

It is important to use 0 for the swi argument because backward compatibility with legacy ABI userspace relies on this. The syscall macros in asm-arm/unistd.h were also updated to support both ABIs and implement the right call method automatically.

13 #ifndef __ASM_ARM_UNISTD_H14 #define __ASM_ARM_UNISTD_H15 #define __NR_OABI_SYSCALL_BASE 0x90000016 #if defined(__thumb__) || defined(__ARM_EABI__)17 #define __NR_SYSCALL_BASE 018 #else19 #define __NR_SYSCALL_BASE

__NR_OABI_SYSCALL_BASE20 #endif

./include/asm-arm/unistd.h

fc6#> arm_v5t_le-objdump -xlD vmlinux | less

private flags = 602: [APCS-32] [VFP float format] ₩[software FP] [has entry point]

fc6#> arm_v5t_le-objdump -xlD vmlinux | grep lessor arm_v5t_le-objdump -xlD /tftpboot/target/init | less

private flags = 4000002: [Version4 EABI] [has entry point]


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Part 3 Legacy ABI vs. EABI

* ABI flags passed to binutils: -mabi=apcs-gnu -mfpu=fpa* gcc -dumpmachine: arm-unknown-linux* objdump -x for compiled binary:

abi#>objdump -xlD vmlinux | lessprivate flags = 602: [APCS-32] [VFP float format] [software FP] [has entry point]

* "file" on compiled Fedora binaryELF 32-bit LSB executable, ARM, version 1 (ARM), for GNU/Linux 2.4.20,

dynamically linked (uses shared libs), for GNU/Linux 2.4.20, stripped

Toolchain&

Binary

* ABI flags passed by gcc to binutils:-mabi=aapcs-linux -mfloat-abi=soft -meabi=4

* gcc -dumpmachine: arm-unknown-linux-gnueabi* objdump -x for compiled binary:

eabi#> objdump -xlD vmlinux | grep lessprivate flags = 4000002: [Version4 EABI] [has entry point]

* "file" on compiled binary (under Fedora)ELF 32-bit LSB executable, ARM, version 1 (SYSV), for GNU/Linux 2.6.18,

dymically linked(uses shared libs), for GNU/Linux 2.6.18, stripped

Toolchain&

Binary

Legacy ABI

New EABI


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Part 3 Cross Compiler for EABIIs it possible to run both EABI and non-EABI binaries on the same system?

EABI 관련하여 설명하고 있는 사이트.

Yes, it is possible. However, running a dual-ABI system requires care. If you have an old-ABI system, and want to run EABI binaries, you have several choices. One option is to link your programs statically, using the -static option. However, linking dynamically is generally a superior approach. Generally, toolchains use a different dynamic loader (ld.so.3), so it is possible for old-ABI and EABI binaries to coexist. However, you will have to ensure that when you install the EABI libraries you do not overwrite existing libraries, and you will have to set LD_LIBRARY_PATH so that the dynamic loader can find them.

※ Support EABI Feature“make menuconfig” – “Kernel Features” – “[*]Use the ARM EABI to compile the kernel”


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Part 3 If EABI is not supported in your kernel?

For example, Your kernel is 2.6.15- . So You need EABI Feature.

32arm-eabi-syscall-adjstments16

arm_eabi_syscalls_compat_hack31arm-eabi-syscalls15

arm_mempolicy_syscalls_compat_hack30arm-eabi-helper-func-names14

arm-oabi-struct-sockaddr_un29arm-eabi-sp-align-213

arm-oabi-is-experimental28arm-eabi-sp-align-112

arm-nptl-compat-mb27arm-eabi-slab-align-to-64bits11

arm-eabi-sigreturn-fix26arm-eabi-relocs-for-modules10

arm-oabi-kconfig25arm_mno-thumb-interwork9

arm-oabi-nwfpe24arm-fix-sys_sendto-and-sys_recvfrom-6-arg8

arm-oabi-multi-abi23slab-add-more-arch-override7

arm-oabi-syscall-wrappers22arm-optimized-libc-functions6

arm-oabi-statfs6421arm-remove-udivdi3-from-kernel5

arm-mempolicy-syscalls20arm-remove-udivdi3-from-nwfpe4

arm-inotify-ioprio.syscalls19mmc-remove-ref-to-divdi33

arm-update-syscall-table18arm-remove-udivdi3-from-pxafb2

arm-eabi-kconfig17use_mtune_arm1136j-s_for_ARMv6_targets1

•On any ARM toolchain (v5t_le, xscale_le), in the Processor Features area, the following new freatures need to be set EABI.

Low Memory Killer4.

PART 1. Overview

PART 2. OpenBinder

PART 3. EABI



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Part 4 What is Low Memory Killer?Why Google develop Low Memory Killer without OOM?

TargetBoard에서 사용가능한 메모리 공간이 고갈 상태에 이르렀을 때, OOM(Out Of Memory)을 발생시키는 방법을 사용하지 않고, 프로세스들의 중요도에 따라 그룹으로 나눈 후에 중요도가 낮은 그룹에 있는 Process부터 하나씩 하나씩 Kill하여 Android의 전체적인 시스템의 운영을 유지시켜주는 메모리를 확보하는 방법이다. 아래는 메모리가 고갈 상태에 이르렀을 때 Low Memory Killer가 작동되면서 udev 프로세스를 Kill하는 것을 보여주고있다.

………………………… 윗부분 생략 ……………………………….

printk: 8 messages suppressed.oom-killer: gfp_mask=0x201d2, order=0Mem-info:DMA per-cpu:cpu 0 hot: high 18, batch 3 used:12cpu 0 cold: high 6, batch 1 used:2DMA32 per-cpu: emptyNormal per-cpu: emptyHighMem per-cpu: emptyFree pages: 1436kB (0kB HighMem)Active:6717 inactive:1641 dirty:0 writeback:0 unstable:0 free:359 slab:1458 mapped:61 pagetables:1700DMA free:1436kB min:1024kB low:1280kB high:1536kB active:26868kB inactive:6564kB present:65536kB pages_scanned:14954 all_unreclaimable? no

lowmem_reserve[]: 0 0 0 0DMA32 free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? nolowmem_reserve[]: 0 0 0 0Normal free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? nolowmem_reserve[]: 0 0 0 0HighMem free:0kB min:128kB low:128kB high:128kB active:0kB inactive:0kB present:0kB pages_scanned:0

all_unreclaimable? nolowmem_reserve[]: 0 0 0 0DMA: 51*4kB 26*8kB 4*16kB 0*32kB 1*64kB 1*128kB 1*256kB 1*512kB 0*1024kB 0*2048kB 0*4096kB = 1436kBDMA32: emptyNormal: emptyHighMem: emptySwap cache: add 0, delete 0, find 0/0, race 0+0Free swap = 0kBTotal swap = 0kBOut of Memory: Kill process 908 (udevd) score 122 and children.Out of memory: Killed process 1922 (udev).Free swap: 0kB16384 pages of RAM2623 free pages924 reserved pages1458 slab pages279 pages shared0 pages swap cached………………………… 아랫 부분 생략 ……………………………….

•“ lowmem_reserver” 부분 kernel-2.6/mm/page_alloc.c 파일의show_free_areas( ) 함수 안의 for_each_zone() 함수에서 담당


2008 Korea Android

Part 4 OOM (Out of Memory ) Killer

: gfp_mask=0x201d2, order=0

[<c0144b11>] out_of_memory+0x25/0x144[<c0145fa7>] __alloc_pages+0x1f5/0x275[<c0147117>] __do_page_cache_readahead+0xc8/0x1e8[<c01162e5>] __wake_up_common+0x2f/0x53[<c0116755>] __wake_up+0x2a/0x3d[<c014420e>] filemap_nopage+0x151/0x30b[<c014c731>] __handle_mm_fault+0x24e/0x705[<c01248a3>] do_gettimeofday+0x31/0xce[<c011554e>] do_page_fault+0x18a/0x46c[<c01153c4>] do_page_fault+0x0/0x46c[<c01037d5>] error_code+0x39/0x40

Mem-info:DMA per-cpu:cpu 0 hot: high 0, batch 1 used:0

…………. Below Omission …………….

Free pages: 21472kB (340kB HighMem)…………. Below Omission …………….

OOM Example

※ Kernel Messages Analysis: This is caused by DMA problem. Physical HDD’s Problem? In fact , This Memory Allocation Policy Related Problem.

Program is allocating memory continually.while (1) {

if (malloc(1<<50) == NULL) {printf("malloc failure after %d MiB₩n", n);return 0; }

printf ("Got %d Mb₩n", ++n);}

Program allocate memory, and use memory immediately. while (1) {

if ((Temp = malloc(1<<50)) == NULL) {printf("malloc failure after %d MiB₩n", n);return 0;}

memset (p, 0, (1<<50));printf ("Got %d Mb₩n", ++n);

}

Allocate needed memory using for(), Use allocated memory using for().for (n = 0; num < 50,000 ; n++) {

temp[num] = malloc(1<<50);if (temp[num] == NULL)break;

}printf("malloc failure after %d MiB₩n", n);for (i = 0; i < num; i++) {

memset ( pp[i], 0, (1<<50) );printf("Got %d Mb₩n", i+1);

}

Kenrle Messages When OOM

※ Case 3에서 OOM killer는 init를 제외한 현재 실행중인 모든

Process들을 검사 Memory Usage에 따라 Score 부여이때

superuser Process나 Hardware를 Access중인 Process는 점수

가 1/4로 삭감 Score가 가장 많은 Process를 Kill함.

Guide for Embedded Memory Programming

• What Every Programmer Should Know About Memory

• Understanding The Linux Virtual Memory manager

• Understanding Virtual Memory in Red Hat Enterprise Linux 4


2008 Korea Android

Part 4 Android Application ‘s Life Cycle 1/2How do we make Application’s life cycle in Mobile/Embedded?

안드로이드의 중요하면서 보편적이지 않은 하나의 특징은 애플리케이션 프로세스의 생명주기가 해당 애플리케이션에 의해 직접적으로 제어되지 않는 다는 것이다. 대신, 애플리케이션이 사용자를 위해서 얼마나 중요한가? 그리고 시스템 전체적으로 얼마나 많은 메모리가 유용한가라는 애플리케이션 실행과 관련된 시스템의 인식기반과 관련된 애플리케이션의 조합된 영역들에 의해 결정난다.

empty 프로세스는 어떤 활성화 된 애플리케이션 컴포넌트도 점유하지 않는 프로세스이다. 이러한 프로세스를 유지하고있는 유일한 이유는 다음번에 해당 애플리케이션을 실행할 필요가 있을 때 시동(startup) 시간을 개선하기 위한 캐쉬로써사용하기 위함이다. 그런 이유로, 시스템은 이러한 캐쉬화된 empty 프로세스들과 기반에 있는 커널 캐쉬들 사이에서 전반적인 시스템 균형을 유지하기 위해 이러한 프로세스들을 가끔 종료하게 된다.

Empty

(Unlimited)

background 프로세스는 사용자에게는 현재 보여지지 않는 Activity를 점유하는 프로세스이다. 이러한 프로세스는 사용자에게 어떤 것도 직접적으로 영향을 미치지 않는다. activity 생명주기를 정확하게 구현하기 위해서 마련된 것이며, 시스템은 위의 3가지 프로세스 타입 중 한 가지를 위한 메모리 반환 요청이 있을 시에만 그러한 프로세스를 종료시킬 것이다. 일반적으로 많은 수의 이런 프로세스가 실행되고 있으며, 해당 프로세스들은 메모리 결핍 시 사용자에게 가장 최근에 보여진 것이 가장 마지막에 종료되는 절차를 확립하기 위해 LRU 리스트 상에서 유지된다.

Background

(64M)

service 프로세스는 startService() 메쏘드를 가지고 시작된 Service를 점유하고 있는 프로세스 이다. 이러한 프로세스는사용자에게 직접적으로 보여지는 않지만, 이것은 일반적으로 사용자와 관련된 어떤 일을 일반적으로 수행하며, 시스템이모든 foreground와 visibile 프로세스를 보유하기에 충분한 메모리가 존재하는 한, 시스템은 그러한 프로세스들은 항상 실행상태로 유지할 것이다.

Serivce

(16M)

visible 프로세스는 사용자의 화면상에는 나타나지만 foreground 상태는 아닌 Activity를 점유하는 프로세스이다. 예를 들어 foreground activity 다이얼로그 형태로 그 뒤에 이전에 보여졌던 activity를 허용하면서 표시될때 이러한 것은 발생하게 된다. 그러한 프로세스는 극도록 중요하게 고려되며 더이상 그것을 수행하지 않을 때까지 종료되지 않으며, 모든foreground 프로세스들을 실행 상태로 유지하는 것이 요구된다.

Visible

(8M)

foreground 프로세스는 사용자와 상호작용을 하고 있는 스크린의 최상위에 있는 Activity나 현재 수행되고 있는IntentReceiver를 점유하고 있는 프로세스이다. 시스템에는 매우 작은 수의 그러한 프로세스들이 존재할 뿐이며, 이런 프로세스가 계속 실행 되기조차 어려운 최후의 메모리 부족 상태에서만 종료된다. 일반적으로 디바이스가 메모리 페이징 상태에 도달하는 시점에, 사용자 인터페이스에 대한 응답을 처리하기 위해서 그러한 행위가 요구된다.

Foreground

(6M)

Description계층구조(Free Mem)

http://code.google.com/android/intro/lifecycle.html

Higher

Lower


2008 Korea Android

Part 4 Android Application ‘s Life Cycle 2/2Why Application’s life cycle is important in android platform?

애플리케이션 개발자가 애플리케이션 프로세스의 생명주기에 얼마나 다른 애플리케이션 컴포넌트 (특별히, Activity, Service, 그리고 IntentReceiver) 가 영향을 미치는가를 이해하는 것은 중요하다. 이러한 컴포넌트들을 정확하게 사용하지 않는다면, 시스템이 해당 애플리케이션이 중요한 작업을 수행 하는 동안 해당 프로세스를 종료시키는 결과를 야기할 수 있다. 프로세스 생명주기와 관련된 버그중 일반적인 예가 IntentReceiver가onReceveIntent() 메쏘드내에서 Intent를 받을 때 쓰레드를 시작한 다음 해당 함수를 리턴하는 경우이다. 그러한 리턴이 발생 하면, 시스템은 IntentReceiver가 더이상 활성화되어 있지 않다고 간주하고, 따라서 그 호스팅 프로세스가 더이상 필요하지 않다고 간주한다. (단지, 다른 애플리케이션 컴포넌트가 그 안에서 활성화 되지 않는 한) 따라서, 시스템은 메모리 반환요청이 있는 어떤 시점에선 해당 프로세스를 종료시킬 수 있다. 이문제를 해결하기 위한 해법은 시스템이 해당 프로세스 내에서 행해지고 있는 활성화된 작업이 여전히 존재한다는 것을 알도록 IntentReceiver로 부터 Service를 시작시키는 것이다 .

메모리가 부족할 때, 어떤 프로세스들이 종료되어야 하는가를 결정하기 위해서, Android는 프로세스를 그것안에서 실행되는 컴포넌트와 그러한 컴포넌트의 상태에 기반을 둔 "중요성 계층구조"에 추가함.


2008 Korea Android

.

Part 4 Kernel Module for Low Memory Killer

Location of Low memory killer

•./kernel-2.6/misw/lowmemorykiller/

lowmem_print()module_param_named()module_param_array_named()module_param_array_named()module_param_named()lowmem_init()lowmem_exit()

shrinker lowmem_shrinker Structure

lowmemorykiller.c

Make file to build Lowmemorykiller.ko kernel moduleMakefile

DescriptionFile Name

•Process에 대한 분류방법을 결정할 때, 시스템은 Process내에서 현재 활성화 된 모든 컴포넌트 중에서 가장 중요한 레벨을 얻어낸다.

•Process의 모든 생명주기에 이러한 Activity, Service, 그리고 IntentReceiver 같은 컴포넌트의 각각이 얼마나 영향을 미치는 지에 대해서는 각각에 대한 보다 자세한 문서를 code.google.com을 통해서 열람 가능함.


2008 Korea Android

.

Part 4 About Android’s low memory shrink task

•

if(nr_to_scan > 0)

lowmem_print(3, "lowmem_shrink %d, %x, ofree %d, ma %d₩n", nr_to_scan, gfp_mask, other_free, min_adj);

read_lock(&tasklist_lock);

{

if(p->oomkilladj >= 0 && p->mm) {tasksize = get_mm_rss(p->mm);if(nr_to_scan > 0 && tasksize > 0 && p->oomkilladj >= min_adj) {

if(selected == NULL ||p->oomkilladj > selected->oomkilladj ||(p->oomkilladj == selected->oomkilladj &&tasksize > selected_tasksize)) {

selected = p;selected_tasksize = tasksize;lowmem_print(2, "select %d (%s), adj %d, size %d , to kill₩n",

p->pid, p->comm, p->oomkilladj, tasksize);}

}rem += tasksize;

}}if(selected != NULL) {

lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d₩n",

selected->pid, selected->comm,selected->oomkilladj, selected_tasksize);

rem -= selected_tasksize;}lowmem_print(4, "lowmem_shrink %d, %x, return %d₩n", nr_to_scan, gfp_mask, rem);read_unlock(&tasklist_lock);return rem;

* static size_t lowmem_minfree[6]={3*512, // 6MB = 3 x 5123 x 42*1024, // 8MB = 2 x 1024 x 44*1024, // 16MB= 4 x 1024 x 416*1024, // 64MB = 16x1024 x 4 };

* Default lowmem_debug_level is 2. If you want to debug , use 3+ value

※Linux Cross Reference WebTool http://lxr.linux.no/linux


2008 Korea Android

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