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Android Boot Time
Optimization




Kan-Ru Chen
                    kanru@0xlab.org
                       Sep 09, 2011
Agenda   Motivation
         Boot Time Measurement
         Android Boot Time Analysis
         Reduction Approach
         Hibernation Based Technologies
         We Don't Need Boot-loader
         Demo
         Future Work and Conclusions
Motivation
Boot Time Measurement
Traditional Linux Environment
Printk Times
Linux kernel feature
Built-in since Linux 2.6.11
How to enable?

    Add CONFIG_PRINTK_TIME=y to .config

    Or choose from menuconfig
    Kernel hacking --->
      [*] Show timing information on printks
Printk Times
Output Example
linux$ dmesg
[0.000000] per task-struct memory footprint: 1152 bytes
[0.003692] Calibrating delay loop... 506.27 BogoMIPS (lpj=1978368)
[0.079833] pid_max: default: 32768 minimum: 301
[0.080230] Security Framework initialized
[0.080474] Mount-cache hash table entries: 512
[0.083892] CPU: Testing write buffer coherency: ok

Analysis Tool
linux$ dmesg > timefile
linux$ scripts/show_delta timefile
...
[0.194488 < 0.194488 >] OMAP DMA hardware revision 5.0
[0.259948 < 0.065460 >] bio: create slab <bio-0> at 0
[0.267822 < 0.007874 >] SCSI subsystem initialized
...
initcall_debug
Kernel Parameter
Print the time spent for each initcall
Output Example
calling ipc_init+0x0/0x28 @ 1
msgmni has been set to 42
initcall ipc_init+0x0/0x28 returned 0 after 1872 usecs
Bootchart
Visualize the booting process
Use “bootchartd” to collect CPU and IO utilization
information.
On Ubuntu:
 apt-get install bootchart bootchart-view
Original “bootchartd” is not suitable for embedded
usage.
Bootchart
$ bootchart bootchart.tgz -f png
Strace
Trace system calls during process execution and
output timing information.
$ strace -tt ls
15:11:04.243357 execve("/bin/ls", ["ls"], [/* 51 vars */]) = 0
15:11:04.244252 brk(0)                  = 0x234f000
15:11:04.244458 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT
15:11:04.244676 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|
MAP_ANONYMOUS, -1, 0) = 0x7f1444794000
15:11:04.244852 access("/etc/ld.so.preload", R_OK) = -1 ENOENT
15:11:04.245096 open("/etc/ld.so.cache", O_RDONLY) = 3
OProfile
OProfile is a system-wide profiler for Linux systems.
Capable of profiling all running code at low overhead.
Supports wide number of hardwares.
Profiling daemon ported to Android and available in
AOSP.
OProfile
Output Example
$ opreport --exclude-dependent
CPU: PIII, speed 863.195 MHz (estimated)
Counted CPU_CLK_UNHALTED events (clocks processor is not halted)...
450385 75.6634 cc1plus
 60213 10.1156 lyx
 29313 4.9245 XFree86
 11633 1.9543 as
 10204 1.7142 oprofiled
  7289 1.2245 vmlinux
  7066 1.1871 bash
  6417 1.0780 oprofile
  6397 1.0747 vim
...
Perf
New profiling tool based on the performance counter
subsystem of Linux.
Very powerful and easy to use.
Included in Linux source code:
tools/perf/
Perf
Recording:
$ perf record -a -f
^C
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.288 MB perf.data (~12567 samples)]


Output
$   perf report --sort comm,dso,symbol|head -10
#   Events: 1K cycles
#
#   Overhead       Command            Shared Object         Symbol
#   ........   ...........   ......................   ............
#
      35.47%      firefox    libxul.so                [.]   0xc1b3a7
       3.08%      firefox    libcairo.so.2.11000.2    [.]   0xff88
       2.98%         Xorg    Xorg (deleted)           [.]   0xe201c
       2.51%      firefox    firefox                  [.]   0x2726
       1.49%         Xorg    [kernel.kallsyms]        [k]   find_vma
       0.93%   perf_3.0.0    perf_3.0.0               [.]   hex2u64
Perf
  Timechart
$ perf timechart record
  $ perf timechart
Android Environment
Bootchart
Original “bootchartd” is not suitable on embedded
devices.
Android re-implemented in its “init” program.
Bootchart
To build:
$ cd system/core/init
$ touch init.c
$ mm INIT_BOOTCHART=true
Bootchart
To run:
$ adb shell 'echo 120 > /data/bootchart-start'
Remember the /data directory must be write able
during boot.
Use grab-bootchart.sh to retrieve the data.
Strace
After analyzed the bootchart, can use strace to
analyze individual progarm.
Available in AOSP since Éclair
Strace
Modify init.rc from
service zygote /system/bin/app_process -Xzygote /system/bin 
                             --zygote --start-system-server




To
 service zygote /system/xbin/strace -tt -o/data/boot.strace 
                /system/bin/app_process -Xzygote /system/bin 
                              --zygote --start-system-server
Logcat
Android log utility
Can output timing information
Adjust loglevel to 6 in init.rc

    Displays time spent for each command
Dalvik Method Tracer
Method tracer is built into Dalvik
Use DDMS or using calls inside source to collect data.
// start tracing to "/sdcard/calc.trace"
Debug.startMethodTracing("calc");
// ...
// stop tracing
Debug.stopMethodTracing();
Stopwatch
Not real stopwatch
A utility in Android Framework for measuring C++
code.
Output result to system log
#include <utils/StopWatch.h>
…
{
    StopWatch watch("blah");
    /* your codes here */
}
Q&A
Android Boot Time Analysis
Boot-loader Init
Usually constant time
Avoid init hardware multiple times
Ensure to use maximum CPU frequency
Use faster NAND/MMC reading mechanism
Kernel Init
Mostly usual suspects

    ip_auto_config

    USB init

    Flash driver initialization

Fullow the standard Kernel optimizing guide:
   http://elinux.org/Boot_Time

Avoid loading unneeded kernel module at boot time
Zygote Class Preloading
Android Framework has thousands of Java classes
Preloaded by Zygote and instantiated in its heap
To improve Application startup time and save memory
Controlled by resource: preloaded-classes

    frameworks/base/preloaded-classes
Zygote Class Preloading
Can use the tool in framework to adjust the list:
$ adb logcat > logcat.txt
$ java -p preload.jar Compile logcat.txt logcat.compiled
$ java -p preload.jar PrintCsv logcat.compiled

Google Android Developer Dianne Hackborn said:

    The content of the file is a “black art”

    You can adjust this as much as you like

    But the result maybe suboptimal
PackageManager Package Scannig
Every APK is scanned at boot time
Package management code is inefficient
Uses mmaped files means each access will cause
page fault
ParseZipArchive() scans entire APK for only one
AndroidManifest.xml file
System Services Starting
Last stage of Android boot
Start every base service
Zygote start SystemServer process
Start native service (SurfaceFlinger, AudioFlinger) first
Start each service sequentially
Q&A
Reduction Approach
Boot-loader
Improve U-Boot

    Reading multi-mmc-block

    Cache (I/D) enablement

    Optimize CRC32

    Disable verification
Boot-loader
Qi Boot-loader
                                                        Qi           U-Boot + XLoader
                                                        Boot-oader
                                       Size             ~30K         ~270K+20K

    Only one stage boot-loader         Time to Kernel   <1s          > 5s


    Small footprint ~30K               Usage            Product      Engineering

                                       Code             Simple       Complicated

    Currently support
     −   iMX31
     −   Samsung 24xx
     −   Beagleboard

    KISS concept
     −   Boot device and load kernel
Kernel Boot Time
Fullow the standard Kernel optimizing guide:
   http://elinux.org/Boot_Time

Minimize kernel size
Use compression or not
Enable embedded options
Avoid loading unneeded kernel module at boot time
Optimize Android Init
Parallize init tasks

    insmod cannot be parallized

    Use external scripts to init at background

Start services on demand
Optimize Class Preloading
Trade-off between preload class and application
startup time
Split class to more packages to reduce dependency
Save inited heap for later use
Share heaps between zygote and children
Filesystem Optimization
According to reasearch by Linaro Kernel WG
Use correct NAND configuration will improve the
performance
MMC controllers are often optimized for particular
usage / filesystem
Adjust the filesystem partition scheme
Toothpaste Effect
Observed by Sony Developer Tim Bird
“When you squeeze a tube of toothpaste, sometimes
it just moves the toothpaste somewhere else in the
tube, and nothing actually comes out.”
Q&A
Hibernation Based Technologies
QuickBoot
Developed by Japanese
company Ubiquitous
Demand loading of
required page from flash
Requires deep
integration of hardware
and software
Fast-On
Developed by CCU
Based on existing technologies thus requires little
modification to userspace
Release clean-pages before suspend
Swap out dirty-pages before save image
Image size reduced leads to faster resume time.
Android Wakelocks & TuxOnIce
TuxOnIce Patch
TuxOnIce (was Software Suspend 2) is a hibernation
patchset
Can save images to different locations
Can use different compresion algorithm
Porting to ARM is possible
Android Wakelocks
An aggressive approach to save device power
Use wakelocks to prevent device going suspend
Port TOI to Android have to deal with wakelocks
because MMC driver might hold a wakelock
Linux Suspend Architecture
Documentation/power/devices.txt:
  struct dev_pm_ops {
          int (*prepare)(struct device *dev);
          void (*complete)(struct device *dev);
          int (*suspend)(struct device *dev);
          int (*resume)(struct device *dev);
          int (*freeze)(struct device *dev);
          int (*thaw)(struct device *dev);
          int (*poweroff)(struct device *dev);
          int (*restore)(struct device *dev);
          int (*suspend_noirq)(struct device *dev);
          int (*resume_noirq)(struct device *dev);
          int (*freeze_noirq)(struct device *dev);
          int (*thaw_noirq)(struct device *dev);
          int (*poweroff_noirq)(struct device *dev);
          int (*restore_noirq)(struct device *dev);
          int (*runtime_suspend)(struct device *dev);
          int (*runtime_resume)(struct device *dev);
          int (*runtime_idle)(struct device *dev);
  };
Q&A
We Don't Need Boot-loader
R-Loader
Normal suspend-to-disk approach has many
duplicated effort

    Boot-loader inits some hardwares

    Boot-loader loads the normal kernel image

    Kernel inits some hardwares again

    Kernel loads the suspended kernel image

    Kernel resumes, inits some hardwares again
R-Loader
0xlab Developer Matt Proposed “Resume-Loader”
R-Loader inits some hardware then reads the
suspended kernel image as fast as possible
Jump directly to the resume point
Kernel will takeover the job and inits reset hardwares
Demo
Get 0xdroid 0x7 release
   https://code.google.com/p/0xdroid/wiki/0x7_leb_gingerbread

Get TOI Patch for 0x7 release
   https://gitorious.org/0xlab-kernel/kernel/commits/toi/linaro-android.38
Future Work and Conclusions
Save the heap image (like core dump) of Zygote after
preloading classes
Modify Dalvik to make hibernation image after system
init and before Launcher startup
Parallize Android init
Cache & Share JITed code fragment
Q&A
http://0xlab.org

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Android Boot Time Optimization

  • 1. Connect your device to application
  • 2. Android Boot Time Optimization Kan-Ru Chen kanru@0xlab.org Sep 09, 2011
  • 3. Agenda Motivation Boot Time Measurement Android Boot Time Analysis Reduction Approach Hibernation Based Technologies We Don't Need Boot-loader Demo Future Work and Conclusions
  • 7. Printk Times Linux kernel feature Built-in since Linux 2.6.11 How to enable?  Add CONFIG_PRINTK_TIME=y to .config  Or choose from menuconfig Kernel hacking ---> [*] Show timing information on printks
  • 8. Printk Times Output Example linux$ dmesg [0.000000] per task-struct memory footprint: 1152 bytes [0.003692] Calibrating delay loop... 506.27 BogoMIPS (lpj=1978368) [0.079833] pid_max: default: 32768 minimum: 301 [0.080230] Security Framework initialized [0.080474] Mount-cache hash table entries: 512 [0.083892] CPU: Testing write buffer coherency: ok Analysis Tool linux$ dmesg > timefile linux$ scripts/show_delta timefile ... [0.194488 < 0.194488 >] OMAP DMA hardware revision 5.0 [0.259948 < 0.065460 >] bio: create slab <bio-0> at 0 [0.267822 < 0.007874 >] SCSI subsystem initialized ...
  • 9. initcall_debug Kernel Parameter Print the time spent for each initcall Output Example calling ipc_init+0x0/0x28 @ 1 msgmni has been set to 42 initcall ipc_init+0x0/0x28 returned 0 after 1872 usecs
  • 10. Bootchart Visualize the booting process Use “bootchartd” to collect CPU and IO utilization information. On Ubuntu: apt-get install bootchart bootchart-view Original “bootchartd” is not suitable for embedded usage.
  • 12. Strace Trace system calls during process execution and output timing information. $ strace -tt ls 15:11:04.243357 execve("/bin/ls", ["ls"], [/* 51 vars */]) = 0 15:11:04.244252 brk(0) = 0x234f000 15:11:04.244458 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT 15:11:04.244676 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE| MAP_ANONYMOUS, -1, 0) = 0x7f1444794000 15:11:04.244852 access("/etc/ld.so.preload", R_OK) = -1 ENOENT 15:11:04.245096 open("/etc/ld.so.cache", O_RDONLY) = 3
  • 13. OProfile OProfile is a system-wide profiler for Linux systems. Capable of profiling all running code at low overhead. Supports wide number of hardwares. Profiling daemon ported to Android and available in AOSP.
  • 14. OProfile Output Example $ opreport --exclude-dependent CPU: PIII, speed 863.195 MHz (estimated) Counted CPU_CLK_UNHALTED events (clocks processor is not halted)... 450385 75.6634 cc1plus 60213 10.1156 lyx 29313 4.9245 XFree86 11633 1.9543 as 10204 1.7142 oprofiled 7289 1.2245 vmlinux 7066 1.1871 bash 6417 1.0780 oprofile 6397 1.0747 vim ...
  • 15. Perf New profiling tool based on the performance counter subsystem of Linux. Very powerful and easy to use. Included in Linux source code: tools/perf/
  • 16. Perf Recording: $ perf record -a -f ^C [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.288 MB perf.data (~12567 samples)] Output $ perf report --sort comm,dso,symbol|head -10 # Events: 1K cycles # # Overhead Command Shared Object Symbol # ........ ........... ...................... ............ # 35.47% firefox libxul.so [.] 0xc1b3a7 3.08% firefox libcairo.so.2.11000.2 [.] 0xff88 2.98% Xorg Xorg (deleted) [.] 0xe201c 2.51% firefox firefox [.] 0x2726 1.49% Xorg [kernel.kallsyms] [k] find_vma 0.93% perf_3.0.0 perf_3.0.0 [.] hex2u64
  • 17. Perf Timechart $ perf timechart record $ perf timechart
  • 19. Bootchart Original “bootchartd” is not suitable on embedded devices. Android re-implemented in its “init” program.
  • 20. Bootchart To build: $ cd system/core/init $ touch init.c $ mm INIT_BOOTCHART=true
  • 21. Bootchart To run: $ adb shell 'echo 120 > /data/bootchart-start' Remember the /data directory must be write able during boot. Use grab-bootchart.sh to retrieve the data.
  • 22. Strace After analyzed the bootchart, can use strace to analyze individual progarm. Available in AOSP since Éclair
  • 23. Strace Modify init.rc from service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server To service zygote /system/xbin/strace -tt -o/data/boot.strace /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
  • 24. Logcat Android log utility Can output timing information Adjust loglevel to 6 in init.rc  Displays time spent for each command
  • 25. Dalvik Method Tracer Method tracer is built into Dalvik Use DDMS or using calls inside source to collect data. // start tracing to "/sdcard/calc.trace" Debug.startMethodTracing("calc"); // ... // stop tracing Debug.stopMethodTracing();
  • 26. Stopwatch Not real stopwatch A utility in Android Framework for measuring C++ code. Output result to system log #include <utils/StopWatch.h> … { StopWatch watch("blah"); /* your codes here */ }
  • 27. Q&A
  • 28. Android Boot Time Analysis
  • 29. Boot-loader Init Usually constant time Avoid init hardware multiple times Ensure to use maximum CPU frequency Use faster NAND/MMC reading mechanism
  • 30. Kernel Init Mostly usual suspects  ip_auto_config  USB init  Flash driver initialization Fullow the standard Kernel optimizing guide:  http://elinux.org/Boot_Time Avoid loading unneeded kernel module at boot time
  • 31. Zygote Class Preloading Android Framework has thousands of Java classes Preloaded by Zygote and instantiated in its heap To improve Application startup time and save memory Controlled by resource: preloaded-classes  frameworks/base/preloaded-classes
  • 32. Zygote Class Preloading Can use the tool in framework to adjust the list: $ adb logcat > logcat.txt $ java -p preload.jar Compile logcat.txt logcat.compiled $ java -p preload.jar PrintCsv logcat.compiled Google Android Developer Dianne Hackborn said:  The content of the file is a “black art”  You can adjust this as much as you like  But the result maybe suboptimal
  • 33. PackageManager Package Scannig Every APK is scanned at boot time Package management code is inefficient Uses mmaped files means each access will cause page fault ParseZipArchive() scans entire APK for only one AndroidManifest.xml file
  • 34. System Services Starting Last stage of Android boot Start every base service Zygote start SystemServer process Start native service (SurfaceFlinger, AudioFlinger) first Start each service sequentially
  • 35. Q&A
  • 37. Boot-loader Improve U-Boot  Reading multi-mmc-block  Cache (I/D) enablement  Optimize CRC32  Disable verification
  • 38. Boot-loader Qi Boot-loader Qi U-Boot + XLoader Boot-oader Size ~30K ~270K+20K  Only one stage boot-loader Time to Kernel <1s > 5s  Small footprint ~30K Usage Product Engineering Code Simple Complicated  Currently support − iMX31 − Samsung 24xx − Beagleboard  KISS concept − Boot device and load kernel
  • 39. Kernel Boot Time Fullow the standard Kernel optimizing guide:  http://elinux.org/Boot_Time Minimize kernel size Use compression or not Enable embedded options Avoid loading unneeded kernel module at boot time
  • 40. Optimize Android Init Parallize init tasks  insmod cannot be parallized  Use external scripts to init at background Start services on demand
  • 41. Optimize Class Preloading Trade-off between preload class and application startup time Split class to more packages to reduce dependency Save inited heap for later use Share heaps between zygote and children
  • 42. Filesystem Optimization According to reasearch by Linaro Kernel WG Use correct NAND configuration will improve the performance MMC controllers are often optimized for particular usage / filesystem Adjust the filesystem partition scheme
  • 43. Toothpaste Effect Observed by Sony Developer Tim Bird “When you squeeze a tube of toothpaste, sometimes it just moves the toothpaste somewhere else in the tube, and nothing actually comes out.”
  • 44. Q&A
  • 46. QuickBoot Developed by Japanese company Ubiquitous Demand loading of required page from flash Requires deep integration of hardware and software
  • 47. Fast-On Developed by CCU Based on existing technologies thus requires little modification to userspace Release clean-pages before suspend Swap out dirty-pages before save image Image size reduced leads to faster resume time.
  • 49. TuxOnIce Patch TuxOnIce (was Software Suspend 2) is a hibernation patchset Can save images to different locations Can use different compresion algorithm Porting to ARM is possible
  • 50. Android Wakelocks An aggressive approach to save device power Use wakelocks to prevent device going suspend Port TOI to Android have to deal with wakelocks because MMC driver might hold a wakelock
  • 51. Linux Suspend Architecture Documentation/power/devices.txt: struct dev_pm_ops { int (*prepare)(struct device *dev); void (*complete)(struct device *dev); int (*suspend)(struct device *dev); int (*resume)(struct device *dev); int (*freeze)(struct device *dev); int (*thaw)(struct device *dev); int (*poweroff)(struct device *dev); int (*restore)(struct device *dev); int (*suspend_noirq)(struct device *dev); int (*resume_noirq)(struct device *dev); int (*freeze_noirq)(struct device *dev); int (*thaw_noirq)(struct device *dev); int (*poweroff_noirq)(struct device *dev); int (*restore_noirq)(struct device *dev); int (*runtime_suspend)(struct device *dev); int (*runtime_resume)(struct device *dev); int (*runtime_idle)(struct device *dev); };
  • 52. Q&A
  • 53. We Don't Need Boot-loader
  • 54. R-Loader Normal suspend-to-disk approach has many duplicated effort  Boot-loader inits some hardwares  Boot-loader loads the normal kernel image  Kernel inits some hardwares again  Kernel loads the suspended kernel image  Kernel resumes, inits some hardwares again
  • 55. R-Loader 0xlab Developer Matt Proposed “Resume-Loader” R-Loader inits some hardware then reads the suspended kernel image as fast as possible Jump directly to the resume point Kernel will takeover the job and inits reset hardwares
  • 56. Demo Get 0xdroid 0x7 release  https://code.google.com/p/0xdroid/wiki/0x7_leb_gingerbread Get TOI Patch for 0x7 release  https://gitorious.org/0xlab-kernel/kernel/commits/toi/linaro-android.38
  • 57. Future Work and Conclusions Save the heap image (like core dump) of Zygote after preloading classes Modify Dalvik to make hibernation image after system init and before Launcher startup Parallize Android init Cache & Share JITed code fragment
  • 58. Q&A