tifast

tifast is a JVMTI agent designed for profiling the performance impact listening to various JVMTI events. It is called tifast since none of the event handlers do anything meaning that it can be considered speed-of-light.

Usage

Build

make libtifast

The libraries will be built for 32-bit, 64-bit, host and target. Below examples assume you want to use the 64-bit version.

Command Line

The agent is loaded using -agentpath like normal. It takes arguments in the following format:

`[log,][EventName1[,EventName2[,...]]]`

  • If 'log' is the first argument the event handlers will LOG(INFO) when they are called. This behavior is static. The no-log methods have no branches and just immediately return.

  • If 'all' is one of the arguments all events the current runtime is capable of providing will be listened for and all other arguments (excepting 'log') will be ignored.

  • The event-names are the same names as are used in the jvmtiEventCallbacks struct.

  • All required capabilities are automatically gained. No capabilities other than those needed to listen for the events are gained.

  • Only events which do not require additional function calls to cause delivery and are sent more than once are supported.

Supported events

The following events may be listened for with this agent

  • SingleStep

  • MethodEntry

  • MethodExit

  • NativeMethodBind

  • Exception

  • ExceptionCatch

  • ThreadStart

  • ThreadEnd

  • ClassLoad

  • ClassPrepare

  • ClassFileLoadHook

  • CompiledMethodLoad

  • CompiledMethodUnload

  • DynamicCodeGenerated

  • DataDumpRequest

  • MonitorContendedEnter

  • MonitorContendedEntered

  • MonitorWait

  • MonitorWaited

  • ResourceExhausted

  • VMObjectAlloc

  • GarbageCollectionStart

  • GarbageCollectionFinish

All other events cannot be listened for by this agent. Most of these missing events either require the use of other functions in order to be called (FramePop, ObjectFree, etc) or are only called once (VMInit, VMDeath, etc).

ART

art -Xplugin:$ANDROID_HOST_OUT/lib64/libopenjdkjvmti.so '-agentpath:libtifast.so=MethodEntry' -cp tmp/java/helloworld.dex -Xint helloworld

  • -Xplugin and -agentpath need to be used, otherwise the agent will fail during init.
  • If using libartd.so, make sure to use the debug version of jvmti.

adb shell setenforce 0

adb push $ANDROID_PRODUCT_OUT/system/lib64/libtifast.so /data/local/tmp/

adb shell am start-activity --attach-agent /data/local/tmp/libtifast.so=MonitorWait,ClassPrepare some.debuggable.apps/.the.app.MainActivity

RI

java '-agentpath:libtifast.so=MethodEntry' -cp tmp/helloworld/classes helloworld