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88 lines
3.1 KiB
88 lines
3.1 KiB
7 months ago
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============================
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'hotspot' PROBES DESCRIPTION
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============================
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This directory contains D scripts which demonstrate usage of 'hotspot' provider probes.
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The 'hotspot' provider makes available probes that can be used to track the
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lifespan of the VM, thread start and stop events, GC and memory pool
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statistics, method compilations, and monitor activity. With a startup flag,
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additional probes are enabled which can be used to monitor the running Java
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program, such as method enter and return probes, and object allocations. All
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of the hotspot probes originate in the VM library (libjvm.so), so they are
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also provided from programs which embed the VM.
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Many of the probes in the provider have arguments that can be examined to
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provide further details on the state of the VM. Many of these probes'
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arguments are opaque IDs which can be used to link probe firings to each
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other, however strings and other data are also provided. When string values
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are provided, they are always present as a pair: a pointer to unterminated
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modified UTF-8 data (see JVM spec: 4.4.7) , and a length value which
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indicates the extent of that data. Because the string data (even when none
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of the characters are outside the ASCII range) is not guaranteed to be
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terminated by a NULL character, it is necessary to use the length-terminated
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copyinstr() intrinsic to read the string data from the process.
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You can find more information about HotSpot probes here:
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http://java.sun.com/javase/6/docs/technotes/guides/vm/dtrace.html
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===========
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THE SCRIPTS
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===========
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The following scripts/samples which demonstrate 'hotspot' probes usage are
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available:
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- class_loading_stat.d
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The script collects statistics about loaded and unloaded Java classes and
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dump current state to stdout every N seconds.
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- gc_time_stat.d
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The script measures the duration of a time spent in GC.
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The duration is measured for every memory pool every N seconds.
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- hotspot_calls_tree.d
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The script prints calls tree of fired 'hotspot' probes.
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- method_compile_stat.d
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The script prints statistics about N methods with largest/smallest
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compilation time every M seconds.
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- method_invocation_stat.d
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The script collects statistics about Java method invocations.
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- method_invocation_stat_filter.d
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The script collects statistics about Java method invocations.
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You can specify package, class or method name to trace.
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- method_invocation_tree.d
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The script prints tree of Java and JNI method invocations.
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- monitors.d
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The script traces monitor related probes.
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- object_allocation_stat.d
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The script collects statistics about N object allocations every M seconds.
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==========
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HOW TO RUN
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==========
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To run any D script from hotspot directory you can do either:
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# dscript.d -c "java ..."
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or if you don't have Solaris 10 patch which allows to specify probes that
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don't yet exist ( Hotspot DTrace probes are defined in libjvm.so and as
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result they could be not been yet loaded when you try to attach D script to
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the Java process) do:
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# ../helpers/dtrace_helper.d -c "java ..." dscript.d
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or if your application is already running you can just simply attach
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the D script like:
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# dscript.d -p JAVA_PID
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