Drowsy Power Management. Matthew Lentz James Litton Bobby Bhattacharjee University of Maryland

Transcription

1 Drowsy Power Management Matthew Lentz James Litton Bobby Bhattacharjee University of Maryland

2 Background Energy Consumption Mobile devices consume energy without human-interaction Many (periodic) short-lived events executed: Fetch Remote Data Communicate with Nearby Device(s) Receive Push Notification Sample Sensor(s)...

3 Power Trace with Events

4 Power Trace with Events Event = Pull data from remote server over WiFi Event Event

5 Power Management States Event On Suspend System in low-power state Memory retains contents Off

6 Power Management States On On On Event Suspend System in low-power state Memory retains contents Off

7 Power Management States On Suspend On On Event Suspend System in low-power state Memory retains contents Off

8 Power Management States On Suspend On On Event WiFi Controller Power-Save Mode Suspend System in low-power state Memory retains contents Off

9 Power Trace with Events On Suspend On Event Event

10 Power Trace with Events On Suspend On Event Event

11 What Happens During a Wakeup?

12 What Happens During a Wakeup? Interrupt (from RTC Alarm)

13 What Happens During a Wakeup? Suspend On Interrupt (from RTC Alarm)

14 What Happens During a Wakeup? Suspend On Event Interrupt (from RTC Alarm)

15 What Happens During a Wakeup? Suspend On Event Wakelocks Objects held by applications and drivers When all locks released, can enter Suspend Interrupt (from RTC Alarm)

16 What Happens During a Wakeup? Suspend On Event Interrupt (from RTC Alarm)

17 What Happens During a Wakeup? Suspend On Event On Suspend Interrupt (from RTC Alarm)

18 What Happens During a Wakeup? Acquire wakelock Fetch update over WiFi Set future wakeup alarm Release wakelock Suspend On Event On Suspend Interrupt (from RTC Alarm)

19 Transitions are Inefficient Transitions account for 75% of total energy consumption! Suspend On Event On Suspend

20 Transitions are Inefficient Transitions account for 75% of total energy consumption! Suspend On Event On Suspend Transitions for Other Events RTC Alarm (ALM) Bluetooth Connection (BT2) Push Notification (PSH) Sample Accelerometer (SEN) 85% 32% 89% 23%

21 Transitions are Inefficient Transitions account for 75% of total energy consumption! Suspend On Event On Suspend

22 On Suspend

23 On Suspend Flush filesystem buffers Freeze all tasks Suspend all devices Disable non-boot CPUs Set RAM to self-refresh * Wait for interrupt *

24 On Suspend Flush filesystem buffers Freeze all tasks Suspend all devices Disable non-boot CPUs Set RAM to self-refresh * Wait for interrupt *

25 Suspend On

26 Suspend On Enable CPUs Resume all devices Thaw all tasks

27 Suspend On Enable CPUs Resume all devices Thaw all tasks

28 Drowsy Power Management Wake up only what is necessary

29 Drowsy Power Management Wake up only what is necessary Necessary for Pull Data: { }

30 Drowsy Power Management Wake up only what is necessary { } a Application System Services Necessary for Pull Data: Alarm Device WiFi Device

31 Drowsy Power Management Wake up only what is necessary { } a Application System Services Necessary for Pull Data: Alarm Device WiFi Device Unnecessary: { } USB Device Calendar App Bluetooth Device Input Devices Battery Monitoring Device Power Regulator Devices Power Regulators SD Card Device

32 Drowsy Power Management Construct minimal wake set of tasks and devices

33 Drowsy Power Management Construct minimal wake set of tasks and devices Smallest set that maintains correct behavior

34 Drowsy Power Management Construct minimal wake set of tasks and devices Smallest set that maintains correct behavior Expand on-demand as event progresses

35 Drowsy Power Management Construct minimal wake set of tasks and devices Smallest set that maintains correct behavior Expand on-demand as event progresses Constraint: No modifications to user-space

36 Transitions To/From Drowsy Drowsy Thaw all tasks Flush filesystem buffers Freeze all tasks Resume all devices Enable CPUs Suspend all devices Disable non-boot CPUs 5 Set RAM to self-refresh Suspend

37 Transitions To/From Drowsy Drowsy Thaw previously running tasks Resume all devices Enable CPUs Flush filesystem buffers Freeze all tasks Suspend all devices Disable non-boot CPUs Set RAM to self-refresh Suspend

38 Transitions To/From Drowsy Drowsy On CPU or Run Queue Thaw previously running tasks Resume all devices Enable CPUs Flush filesystem buffers Freeze all tasks Suspend all devices Disable non-boot CPUs Set RAM to self-refresh Suspend

39 Transitions To/From Drowsy Wake Set = { <Prev. Running Tasks> } Thaw previously running tasks Resume all devices Enable CPUs Drowsy Flush filesystem buffers Freeze all tasks Suspend all devices Disable non-boot CPUs Set RAM to self-refresh Suspend

40 Transitions To/From Drowsy Wake Set = { <Prev. Running Tasks> } Drowsy Thaw previously running tasks Resume all devices Enable CPUs Flush filesystem buffers Freeze all tasks Suspend all devices Disable non-boot CPUs Set RAM to self-refresh Suspend

41 Transitions To/From Drowsy Wake Set = { <Prev. { <Prev. Running { <Prev. Running Tasks>, Tasks>, Task, Task Device, } } } Drowsy Thaw previously running tasks Resume all devices Enable CPUs Flush filesystem buffers Freeze all tasks Suspend all devices Disable non-boot CPUs Set RAM to self-refresh Suspend

42 Transitions To/From Drowsy Wake Set = { <Prev. { <Prev. Running { <Prev. Running Tasks>, Tasks>, Task, Task Device, } } } Drowsy Thaw previously running tasks Resume all devices Enable CPUs Flush filesystem buffers Freeze tasks in wake set Suspend devices in wake set Disable non-boot CPUs Set RAM to self-refresh Suspend

43 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Task A Time open() named pipe read() from pipe ioctl() command to device

44 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Task A Time open() named pipe read() from pipe Blocks waiting on condition to be met

45 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Task B Task A Time open() named pipe write() to pipe Satisfies condition read() from pipe Blocks waiting on condition to be met ioctl() command to device

46 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Task B Task A Time open() named pipe write() to pipe Satisfies condition read() from pipe Blocks waiting on condition to be met ioctl() command to device

47 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Frozen Task B Task A Time Suspended

48 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Frozen Task B Task A Time Transition to Suspend (All wakelocks released) Suspended

49 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Frozen Task B Task A Time Transition to Suspend (All wakelocks released) Suspended Transition to Drowsy

50 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Frozen Task B Task A Time Suspended Wake Set = { Task B, Task A } { Task B, Task A, Device }

51 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Frozen Task B Task A Time Suspended Wake Set = { Task B } { Task B, Task A } { Task B, Task A, Device }

52 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Frozen Task B Task A Time Suspended Wake Set = { Task B } { Task B, Task A } { Task B, Task A, Device }

53 Constructing the Wake Set Task States: Run (CPU) Run (I/O) Run (Device I/O) Blocked Frozen Task B Task A Time Suspended Wake Set = { Task B } { Task B, Task A } { Task B, Task A, Device }

54 Drowsy Wake Set: Pull Data Task Device IRQ Wakeup Chained IRQ

55 Drowsy Wake Set: Pull Data Task Device IRQ Wakeup Chained IRQ cpu cpu1 log_main wcnss_wlan.0 wlan0 ision hread anager cpu2 cpu3 binder Compiler Benchmark Worker Binder_4 Binder_3 flush-0:17 anager ActivityManager Binder_1 Binder_1 Binder_2 flush-179:0 s 13 ms 26 ms 41 ms 91 ms 98 ms me ing Tasks) Suspend (Sync Filesystem Buffers)

56 Drowsy Wake Set: Pull Data Task Device IRQ Wakeup Chained IRQ IRQ 48 IRQ 362 IRQ 479 cpu cpu1 log_main wcnss_wlan.0 wlan0 platform msm-ssbi.0 msmgpio pm8921-core Time (ms) rtc-pm8xxx mpdecision cpu2 rtc0 ServerThread cpu3 PowerManager binder alarm /dev/alarm AlarmManager ActivityManager Benchmark Worker Compiler Binder_1 Binder_1 Binder_2 Binder_4 Binder_3 flush-0:17 flush-179:0 0 ms 4 ms 6 ms 13 ms 26 ms 41 ms 91 ms 98 ms Resume (Thaw Running Tasks) Suspend (Sync Filesystem Buffers) 15 tasks thawed & 16 devices resumed 1.8% 1.9%

57 Implementation Implemented Drowsy within Android kernel Platform: Google Nexus 4 ( Mako ) Version: (Fork of Linux 3.4) SLOC: ~4,600

58 Instrumenting Android For determining when to add tasks/devices to wake set

59 Instrumenting Android For determining when to add tasks/devices to wake set

60 Example: file_operations struct file_operations d_fops:.open = &drv_open.read = &drv_read.write = &drv_write

61 Example: file_operations struct file_operations d_fops:.open = &drv_open.read = &drv_read.write = &drowsy_write.write_impl = &drv_write

62 Example: file_operations struct file_operations d_fops:.open = &drv_open.read = &drv_read.write = &drowsy_write.write_impl = &drv_write int drowsy_write(file *f, ) Device *d = filetodevice(f) if(d!state == Suspended) resumedevice(d) f!f_ops.write_impl(f, )

63 Evaluation: Benchmarking On Drowsy Suspend Suspend On Drowsy Release Wakelock Acquire Wakelock Handle I/O Event ALM BT2 PUL PSH SEN Set a future wakeup alarm Accept incoming Bluetooth connection Fetch weather update (and set alarm) Receive incoming push notification Sample the accelerometer (and set alarm)

64 Evaluation: Measurement IPhone VPhone IPhone = VShunt / RShunt Time

65 Evaluation: Measurement IPhone VPhone IPhone = VShunt / RShunt Time

66 Evaluation: Measurement IPhone VPhone VPhoto IPhone = VShunt / RShunt Time

67 Evaluation: Measurement LED Toggled On (Software Timestamp) IPhone VPhone VPhoto IPhone = VShunt / RShunt Time

68 Improvement: Wakeup Events Plus Plus (1 Core, Powersave) (1 Core, Powersave)

69 Improvement: Wakeup Events Plus Plus (1 Core, Powersave) (1 Core, Powersave) Drowsy is 1.5-5x as energy efficient

70 Improvement: Wakeup Events Plus Plus (1 Core, Powersave) (1 Core, Powersave) Drowsy is 1.5-5x as energy efficient cpuidle entered deep idle states more often in the Drowsy state

71 Improvement: Wakeup Events Plus Plus (1 Core, Powersave) (1 Core, Powersave)

72 Wakeup Cycle: Pull Data Android Suspend On Event On Suspend

73 Wakeup Cycle: Pull Data Android Suspend On Event On Suspend Drowsy Suspend Drowsy Event & Wake Set Drowsy Suspend

74 Wakeup Cycle: Pull Data Android Suspend On Event On Suspend Drowsy Suspend Drowsy Event & Wake Set Drowsy Suspend WiFi Tail Energy

75 Improvement: Battery Life

76 Improvement: Battery Life Converges to 0% as the interval increases

77 Improvement: Battery Life Benefits of Drowsy aggregate across all applications on device Converges to 0% as the interval increases

78 Summary Existing power management not optimized for short-lived events Drowsy wakes up the minimal set of tasks and devices is 1.5-5x as energy efficient for short-lived events Source code is available at: