Java性能调优作为大型分布式系统提供高性能服务的必修课，其重要性不言而喻。

好的分析工具能起到事半功倍的效果，利用分析利器JMC、JFR，可以实现性能问题的准确定位。

本文主要阐述如何利用JFR生成性能日志

JMC：Java Mission Control

JFR：Java Flight Recorder

1. 打开JFR

JVM_OPT中添加：-XX:+UnlockCommercialFeatures -XX:+FlightRecorder -Djavax.xml.parsers.SAXParserFactory=com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl"

2. 启动JFR

登陆服务器，找到应用PID，执行命令：jcmd $PID JFR.start name=abc,duration=120s

3. Dump JFR

等待至少duration（本文设定120s）后，执行命令：jcmd $PID JFR.dump name=abc,duration=120s filename=abc.jfr（注意，文件名必须为.jfr后缀）

4. 检查JFR状态

执行命令：jcmd $PID JFR.check name=abc,duration=120s

5. 停止JFR

执行命令：jcmd $PID JFR.stop name=abc,duration=120s

6. JMC分析

切回开发机器，下载步骤3中生成的abc.jfr，打开jmc，导入abc.jfr即可进行可视化分析

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另一种配置方法, 已经成功:

java 参数  -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:NativeMemoryTracking=summary -XX:FlightRecorderOptions=defaultrecording=true

sudo -utomcat jcmd 8588 JFR.start settings=/tmp/my-profiling.jfc duration=6m filename=/tmp/hsperfdata_tomcat/new2.jfr

my-profiling.jfc 这个是模板文件, 内容如下:

<?xml version="1.0" encoding="UTF-8"?>
<configuration version="1.0" name="my-profiling" description="Low overhead configuration for profiling, typically around 2 % overhead." provider="Oracle">

<producer uri="http://www.oracle.com/hotspot/jvm/" label="Oracle JDK">

<control>

<selection name="gc-level" default="detailed" label="Garbage Collector">
        <option label="Off" name="off">off</option>
        <option label="Normal" name="detailed">normal</option>
        <option label="All" name="all">all</option>
      </selection>

<condition name="gc-enabled-normal" true="true" false="false">
        <or>
          <test name="gc-level" operator="equal" value="normal"/>
          <test name="gc-level" operator="equal" value="all"/>
        </or>
      </condition>

<condition name="gc-enabled-all" true="true" false="false">
        <test name="gc-level" operator="equal" value="all"/>
      </condition>

<selection name="compiler-level" default="detailed" label="Compiler">
        <option label="Off" name="off">off</option>
        <option label="Normal" name="normal">normal</option>
        <option label="Detailed" name="detailed">detailed</option>
        <option label="All" name="all">all</option>
      </selection>

<condition name="compiler-enabled" true="false" false="true">
        <test name="compiler-level" operator="equal" value="off"/>
      </condition>

<condition name="compiler-enabled-failure" true="true" false="false">
        <or>
          <test name="compiler-level" operator="equal" value="detailed"/>
          <test name="compiler-level" operator="equal" value="all"/>
        </or>
      </condition>

<condition name="compiler-sweeper-threshold" true="0 ms" false="100 ms">
        <test name="compiler-level" operator="equal" value="all"/>
      </condition>

<condition name="compiler-compilation-threshold" true="1000 ms">
        <test name="compiler-level" operator="equal" value="normal"/>
      </condition>

<condition name="compiler-compilation-threshold" true="100 ms">
        <test name="compiler-level" operator="equal" value="detailed"/>
      </condition>

<condition name="compiler-compilation-threshold" true="0 ms">
        <test name="compiler-level" operator="equal" value="all"/>
      </condition>

<condition name="compiler-phase-threshold" true="60 s">
        <test name="compiler-level" operator="equal" value="normal"/>
      </condition>

<condition name="compiler-phase-threshold" true="10 s">
        <test name="compiler-level" operator="equal" value="detailed"/>
      </condition>

<condition name="compiler-phase-threshold" true="0 s">
        <test name="compiler-level" operator="equal" value="all"/>
      </condition>

<selection name="method-sampling-interval" default="maximum" label="Method Sampling">
        <option label="Off" name="off">999 d</option>
        <option label="Normal" name="normal">20 ms</option>
        <option label="Maximum" name="maximum">10 ms</option>
      </selection>

<condition name="method-sampling-enabled" true="false" false="true">
        <test name="method-sampling-interval" operator="equal" value="999 d"/>
      </condition>

<selection name="thread-dump-interval" default="everyMinute" label="Thread Dump">
        <option label="Off" name="off">999 d</option>
        <option label="At least Once" name="normal">everyChunk</option>
        <option label="Every 60 s" name="everyMinute">60 s</option>
        <option label="Every 10 s" name="everyTenSecond">10 s</option>
        <option label="Every 1 s" name="everySecond">1 s</option>
      </selection>

<condition name="thread-dump-enabled" true="false" false="true">
        <test name="thread-dump-interval" operator="equal" value="999 d"/>
      </condition>

<selection name="exception-level" default="errors" label="Exceptions">
        <option label="Off" name="off">off</option>
        <option label="Errors Only" name="errors">errors</option>
        <option label="All Exceptions, including Errors" name="all">all</option>
      </selection>

<condition name="enable-errors" true="true" false="false">
        <or>
          <test name="exception-level" operator="equal" value="errors"/>
          <test name="exception-level" operator="equal" value="all"/>
        </or>
      </condition>

<condition name="enable-exceptions" true="true" false="false">
        <test name="exception-level" operator="equal" value="all"/>
      </condition>

<text name="synchronization-threshold" label="Synchronization Threshold" contentType="timespan" minimum="0 s">10 ms</text>

<text name="file-io-threshold" label="File I/O Threshold" contentType="timespan" minimum="0 s">10 ms</text>

<text name="socket-io-threshold" label="Socket I/O Threshold" contentType="timespan" minimum="0 s">10 ms</text>

<flag name="heap-statistics-enabled" label="Heap Statistics">false</flag>

<flag name="class-loading-enabled" label="Class Loading">true</flag>

<flag name="allocation-profiling-enabled" label="Allocation Profiling">true</flag>

</control>

<event path="java/statistics/thread_allocation">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="java/statistics/class_loading">
      <setting name="enabled">true</setting>
      <setting name="period">1000 ms</setting>
    </event>

<event path="java/statistics/threads">
      <setting name="enabled">true</setting>
      <setting name="period">1000 ms</setting>
    </event>

<event path="java/thread_start">
      <setting name="enabled">true</setting>
    </event>

<event path="java/thread_end">
      <setting name="enabled">true</setting>
    </event>

<event path="java/thread_sleep">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="synchronization-threshold">10 ms</setting>
    </event>

<event path="java/thread_park">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="synchronization-threshold">10 ms</setting>
    </event>

<event path="java/monitor_enter">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="synchronization-threshold">10 ms</setting>
    </event>

<event path="java/monitor_wait">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="synchronization-threshold">10 ms</setting>
    </event>

<event path="vm/class/load">
      <setting name="enabled" control="class-loading-enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/class/unload">
      <setting name="enabled" control="class-loading-enabled">true</setting>
    </event>

<event path="vm/info">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/initial_system_property">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/prof/execution_sample">
      <setting name="enabled" control="method-sampling-enabled">true</setting>
      <setting name="period" control="method-sampling-interval">10 ms</setting>
    </event>

<event path="vm/prof/execution_sampling_info">
      <setting name="enabled">false</setting>
      <setting name="threshold">1 ms</setting>
    </event>

<event path="vm/runtime/execute_vm_operation">
      <setting name="enabled">true</setting>
      <setting name="threshold">10 ms</setting>
    </event>

<event path="vm/runtime/thread_dump">
      <setting name="enabled" control="thread-dump-enabled">true</setting>
      <setting name="period" control="thread-dump-interval">60 s</setting>
    </event>

<event path="vm/flag/long">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/flag/ulong">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/flag/double">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/flag/boolean">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/flag/string">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/flag/long_changed">
      <setting name="enabled">true</setting>
    </event>

<event path="vm/flag/ulong_changed">
      <setting name="enabled">true</setting>
    </event>

<event path="vm/flag/double_changed">
      <setting name="enabled">true</setting>
    </event>

<event path="vm/flag/boolean_changed">
      <setting name="enabled">true</setting>
    </event>

<event path="vm/flag/string_changed">
      <setting name="enabled">true</setting>
    </event>

<event path="vm/gc/detailed/object_count">
      <setting name="enabled" control="heap-statistics-enabled">false</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/gc/configuration/gc">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/gc/configuration/heap">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/gc/configuration/young_generation">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/gc/configuration/tlab">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/gc/configuration/survivor">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/gc/detailed/object_count_after_gc">
      <setting name="enabled">false</setting>
    </event>

<event path="vm/gc/heap/summary">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/heap/ps_summary">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/heap/metaspace_summary">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/metaspace/gc_threshold">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/metaspace/allocation_failure">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="stackTrace">true</setting>
    </event>

<event path="vm/gc/metaspace/out_of_memory">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="stackTrace">true</setting>
    </event>

<event path="vm/gc/metaspace/chunk_free_list_summary">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/collector/garbage_collection">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/collector/parold_garbage_collection">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/collector/young_garbage_collection">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/collector/old_garbage_collection">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/collector/g1_garbage_collection">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/phases/pause">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/phases/pause_level_1">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/phases/pause_level_2">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/phases/pause_level_3">
      <setting name="enabled" control="gc-enabled-all">false</setting>
      <setting name="threshold">0 ms</setting>
    </event>

<event path="vm/gc/reference/statistics">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/detailed/promotion_failed">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/detailed/evacuation_failed">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/detailed/evacuation_info">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/detailed/concurrent_mode_failure">
      <setting name="enabled" control="gc-enabled-normal">true</setting>
    </event>

<event path="vm/gc/detailed/allocation_requiring_gc">
      <setting name="enabled" control="gc-enabled-all">false</setting>
      <setting name="stackTrace">true</setting>
    </event>

<event path="vm/compiler/config">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/compiler/stats">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="period">1000 ms</setting>
    </event>

<event path="vm/compiler/compilation">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="threshold" control="compiler-compilation-threshold">100 ms</setting>
    </event>

<event path="vm/compiler/phase">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="threshold" control="compiler-phase-threshold">10 s</setting>
    </event>

<event path="vm/compiler/failure">
      <setting name="enabled" control="compiler-enabled-failure">true</setting>
    </event>

<event path="vm/code_sweeper/config">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/code_sweeper/stats">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/code_sweeper/sweep">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="threshold" control="compiler-sweeper-threshold">100 ms</setting>
    </event>

<event path="vm/code_cache/config">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/code_cache/stats">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="vm/code_cache/full">
      <setting name="enabled" control="compiler-enabled">true</setting>
    </event>

<event path="os/information">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="os/processor/cpu_information">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="os/processor/context_switch_rate">
      <setting name="enabled" control="compiler-enabled">true</setting>
      <setting name="period">10 s</setting>
    </event>

<event path="os/processor/cpu_load">
      <setting name="enabled">true</setting>
      <setting name="period">1000 ms</setting>
    </event>

<event path="os/processor/cpu_tsc">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="os/system_process">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="os/initial_environment_variable">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="os/memory/physical_memory">
      <setting name="enabled">true</setting>
      <setting name="period">everyChunk</setting>
    </event>

<event path="java/object_alloc_in_new_TLAB">
      <setting name="enabled" control="allocation-profiling-enabled">true</setting>
      <setting name="stackTrace">true</setting>
    </event>

<event path="java/object_alloc_outside_TLAB">
      <setting name="enabled" control="allocation-profiling-enabled">true</setting>
      <setting name="stackTrace">true</setting>
    </event>

</producer>

<producer uri="http://www.oracle.com/hotspot/jdk/" label="Oracle JDK">

<event path="java/file_read">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="http://www.oracle.com/hotspot/jvm/file-io-threshold">10 ms</setting>
    </event>

<event path="java/file_write">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="http://www.oracle.com/hotspot/jvm/file-io-threshold">10 ms</setting>
    </event>

<event path="java/socket_read">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="http://www.oracle.com/hotspot/jvm/socket-io-threshold">10 ms</setting>
    </event>

<event path="java/socket_write">
      <setting name="enabled">true</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="http://www.oracle.com/hotspot/jvm/socket-io-threshold">10 ms</setting>
    </event>

<event path="java/exception_throw">
      <setting name="enabled" control="http://www.oracle.com/hotspot/jvm/enable-exceptions">false</setting>
      <setting name="stackTrace">true</setting>
    </event>

<event path="java/error_throw">
      <setting name="enabled" control="http://www.oracle.com/hotspot/jvm/enable-errors">true</setting>
      <setting name="stackTrace">true</setting>
    </event>

<event path="java/statistics/throwables">
      <setting name="enabled">true</setting>
      <setting name="period">1000 ms</setting>
    </event>

</producer>

<producer uri="http://www.oracle.com/hotspot/jfr-info/" label="Oracle JDK">

<event path="recordings/recording">
      <setting name="enabled">true</setting>
    </event>

<event path="recordings/recording_setting">
      <setting name="enabled">true</setting>
    </event>

</producer>

</configuration>