| J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 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 |