1 ================================ 2 'hotspot_jni' PROBES DESCRIPTION 3 ================================ 4 5 This directory contains D scripts which demonstrate usage of 'hotspot_jni' 6 provider probes. 7 8 In order to call from native code to Java code, due to embedding of the VM 9 in an application or execution of native code within a Java application, the 10 native code must make a call through the JNI interface. The JNI interface 11 provides a number of methods for invoking Java code and examining the state 12 of the VM. DTrace probes are provided at the entry point and return point 13 for each of these methods. The probes are provided by the hotspot_jni 14 provider. The name of the probe is the name of the JNI method, appended with 15 "-entry" for entry probes, and "-return" for return probes. The arguments 16 available at each entry probe are the arguments that were provided to the 17 function (with the exception of the Invoke* methods, which omit the 18 arguments that are passed to the Java method). The return probes have the 19 return value of the method as an argument (if available). 20 21 You can find more information about HotSpot probes here: 22 http://java.sun.com/javase/6/docs/technotes/guides/vm/dtrace.html 23 24 =========== 25 THE SCRIPTS 26 =========== 27 28 The following scripts/samples which demonstrate hotspot_jni probes usage are 29 available: 30 31 - CriticalSection.d 32 Inspect a JNI application for Critical Section violations. 33 34 - CriticalSection_slow.d 35 Do the same as CriticalSection.d but provide more debugging info. 36 37 - hotspot_jni_calls_stat.d 38 This script collects statistics about how many times particular JNI method 39 has been called. 40 41 - hotspot_jni_calls_tree.d 42 The script prints tree of JNI method calls. 43 44 See more details in the scripts. 45 46 47 ========== 48 HOW TO RUN 49 ========== 50 To run any dscript from hotspot directory you can do either: 51 52 # dscript.d -c "java ..." 53 54 or if you don't have Solaris 10 patch which allows to specify probes that 55 don't yet exist ( Hotspot DTrace probes are defined in libjvm.so and as 56 result they could be not been yet loaded when you try to attach dscript to 57 the Java process) do: 58 59 # ../helpers/dtrace_helper.d -c "java ..." dscript.d 60 61 or if your application is already running you can just simply attach 62 the D script like: 63 64 # dscript.d -p JAVA_PID 65
