AndroidMultiProcessPlayground

An Android app that allows for easy experimention of:

• BIND_* flags for bindService()
• OutOfMemory handling
• Thread priorities

Build & Run:

./gradlew assembleDebug
adb install -r app/build/outputs/apk/app-debug.apk
adb shell am start -n com.example.agrieve.multiprocessdemo/.MainActivity

How to use it

1. Start the app & connect your device with a USB cable
2. On your host machine, navigate to chrome://inspect/#devices
3. Click on the "Stetho" link
4. Type init() into the JS console.
5. Try out example workflows, but DO NOT copy & paste them more than one line at a time or you may execute commands too quickly.

Example Workflow #1 - BIND flags

In devtools:

ren1 = api.createRenderer()
// Show what bindings they have enabled:
api.listBindings()
// Add a custom binding:
api.bindService('Service1', ['BIND_AUTO_CREATE', 'BIND_ADJUST_WITH_ACTIVITY'])
// Remove existing binding:
ren1.moderateBinding.unbind()
// Show OOM buckets via /proc/PID/oom_score_adj
api.listOomScores()

In a terminal:

# See OOM buckets and memory use:
adb shell dumpsys meminfo

Example Workflow #2 - OOM Order and Task Stacks

In devtools:

// Create a process bound to main activity
api.createRenderer()
// Switch to a different activity stack
api.startAffinityActivity()
api.createRenderer()

In a terminal:

# Show which OOM bucket each bound service ends up in.
adb shell dumpsys activity | sed -n -e '/dumpsys activity processes/,$p'
# Note that both services are always together despite being bound by different activities.

Example Workflow #3 - Explicit OOM ordering with BIND_ABOVE_CLIENT

In devtools:

// Create all 8 renderers, and each one create a BIND_ABOVE_CLIENT binding on the previous one.
api.createAllRenderers(0, true);  // First 4.
api.createAllRenderers(0, true);  // Second 4.

In a terminal:

# Show which OOM bucket each bound service ends up in.
adb shell dumpsys activity | sed -n -e '/dumpsys activity processes/,$p'

In devtools:

// Remove all "vis" bindings
renderers.forEach(function(r) { r.moderateBinding.unbind(); })

In a terminal:

# Show which OOM bucket each bound service ends up in.
adb shell dumpsys activity | sed -n -e '/dumpsys activity processes/,$p'
# Switch apps a few times while repeating this step.

Example Workflow #4 - OOM Killing in Action

In devtools:

// Create 4 child services (ren1, ren2, ren3, ren4), have each consume 100meg
api.createAllRenderers(100)
// Show what bindings they have enabled:
api.listBindings()
api.consumeNativeMemoryUntilLow()

In a terminal:

# Watch memory usage go up and apps disappear from cached list
adb shell dumpsys activity | sed -n -e '/dumpsys activity processes/,$p'
# Or use meminfo (but it doesn't show separate background buckets):
adb shell dumpsys meminfo

In devtools:

// This function stops as soon as an onTrimMemory callback is called.
// Call it again to reach the next threshold.
api.consumeNativeMemoryUntilLow()
api.consumeNativeMemoryUntilLow()

Example Workflow #5 - Thread Priorities

In devtools:

// Create 4 native threads, and 4 java threads, all at different priorities.
api.createAllWorkers()
// Show performance of each thread
api.listWorkers()

In a terminal:

# List all threads of the process
adb shell top -n 1 | grep multiprocessdemo
# Monitor CPU usage of top threads
adb shell top -m 20 -t

In devtools:

// Create workers on another process.
api.createAllRenderers()
ren1.createWorker(9)
// Starting at 10, threads go to a low-power cgroup.
ren1.createWorker(10)
api.listWorkers()

Example Workflow #6 - BIND_NOT_FOREGROUND

In devtools:

// Create a workers with & without BIND_NOT_FOREGROUND.
ren1 = api.createRenderer()
ren2 = api.createRenderer(['BIND_NOT_FOREGROUND'])
// Create 2 threads per process of equal priority
ren1.createWorker(0)
ren1.createWorkerNative(0)
ren2.createWorker(0)
ren2.createWorkerNative(0)
// Show performance of each thread
api.listWorkers()

In a terminal:

# Monitor CPU usage of top threads
adb shell top -m 20 -t

Example Workflow #7 - Changing Thread Priorities

In devtools:

api.createWorker(0)
api.createWorker(0)
api.createWorker(10)
// Show performance of each thread
api.listWorkers()

workerThreads[2].setNice(0)
api.resetWorkerStats()
// Show that changed priority worked.
api.listWorkers()

Example Workflow #8 - Querying Current Trim Level

In devtools:

api.createRenderer()
api.createRenderer()
api.createRenderer()
api.printMemoryInfo()  // Look at lastTrimLevel

ren1.consumeNativeMemoryUntilLow()
api.printMemoryInfo()  // lastTrimLevel is now > 0

ren1.moderateBinding.unbind()
ren2.moderateBinding.unbind()
ren3.moderateBinding.unbind()

api.printMemoryInfo()  // lastTrimLevel is now 0 again
// Note also that no onTrimMemory log is shown for this transition.