Java JFR view 试图功能

jcmd

jcmd <pid> JFR.view

输出

PS \openjdk-25> jcmd 7856 JFR.view
7856:
JFR.view
Display event data in predefined views

Impact: Medium

Options:

 cell-height   (Optional) Maximum number of rows in a table cell. (INT, no default value)

 maxage        (Optional) Length of time for the view to span. (INT followed by
               's' for seconds 'm' for minutes or 'h' for hours, default value is 10m)

 maxsize       (Optional) Maximum size for the view to span in bytes if one of
               the following suffixes is not used: 'm' or 'M' for megabytes OR
               'g' or 'G' for gigabytes. (STRING, default value is 32MB)

 truncate      (Optional) How to truncate content that exceeds space in a table cell.
               Mode can be 'beginning' or 'end'. (STRING, default value 'end')

 verbose       (Optional) Displays the query that makes up the view.
               (BOOLEAN, default value false)

 <view>        (Mandatory) Name of the view or event type to display.
               See list below for available views. (STRING, no default value)

 width         (Optional) The width of the view in characters
               (INT, default value is 100)

Java virtual machine views:
 blocked-by-system-gc      gc-concurrent-phases jvm-information
 class-modifications       gc-configuration     longest-compilations
 compiler-configuration    gc-cpu-time          native-memory-committed
 compiler-phases           gc-parallel-phases   native-memory-reserved
 compiler-statistics       gc-pause-phases      safepoints
 deoptimizations-by-reason gc-pauses            tlabs
 deoptimizations-by-site   gc-references        vm-operations
 gc                        heap-configuration

Environment views:
 active-recordings        cpu-load              native-library-failures
 active-settings          cpu-load-samples      network-utilization
 container-configuration  cpu-tsc               recording
 container-cpu-throttling environment-variables system-information
 container-cpu-usage      events-by-count       system-processes
 container-io-usage       events-by-name        system-properties
 container-memory-usage   jvm-flags

Application views:
 allocation-by-class            exception-by-site     method-timing
 allocation-by-site             exception-by-type     modules
 allocation-by-thread           exception-count       monitor-inflation
 class-loaders                  file-reads-by-path    native-methods
 contention-by-address          file-writes-by-path   object-statistics
 contention-by-class            finalizers            pinned-threads
 contention-by-site             hot-methods           socket-reads-by-host
 contention-by-thread           latencies-by-type     socket-writes-by-host
 cpu-time-hot-methods           longest-class-loading thread-allocation
 cpu-time-statistics            memory-leaks-by-class thread-count
 deprecated-methods-for-removal memory-leaks-by-site  thread-cpu-load
 exception-by-message           method-calls          thread-start


 The <view> parameter can be an event type name. Use the 'JFR.view types'
 to see a list. To display all views, use 'JFR.view all-views'. To display
 all events, use 'JFR.view all-events'.

Example usage:

 $ jcmd <pid> JFR.view gc

 $ jcmd <pid> JFR.view width=160 hot-methods

 $ jcmd <pid> JFR.view verbose=true allocation-by-class

 $ jcmd <pid> JFR.view contention-by-site

 $ jcmd <pid> JFR.view jdk.GarbageCollection

 $ jcmd <pid> JFR.view cell-height=5 ThreadStart

 $ jcmd <pid> JFR.view truncate=beginning SystemProcess

查看事件类型

jcmd <pid> JFR.view types

输出：括号中表示目前采集到的事件个数。

PS \openjdk-25> jcmd 1240 JFR.view types
1240:
Event Types (number of events):

 ActiveRecording (1)              JavaMonitorStatistics (1)
 ActiveSetting (379)              JavaMonitorWait (22)
 AllocationRequiringGC            JavaThreadStatistics (438)
 BooleanFlag (489)                LongFlag (137)
 BooleanFlagChanged               LongFlagChanged
 CPUInformation (1)               MetaspaceAllocationFailure (3)
 CPULoad (438)                    MetaspaceChunkFreeListSummary (132)
 CPUTimeStampCounter (1)          MetaspaceGCThreshold (6)
 ClassDefine                      MetaspaceOOM
 ClassLoad                        MetaspaceSummary (66)
 ClassLoaderStatistics (3)        MethodTiming (4959)
 ClassLoadingStatistics (438)     MethodTrace
 ClassRedefinition (1)            ModuleExport
 ClassUnload                      ModuleRequire
 CodeCacheConfiguration (1)       NativeAgent
 CodeCacheFull                    NativeLibrary (48)
 CodeCacheStatistics (1)          NativeLibraryLoad (5)
 Compilation                      NativeLibraryUnload
 CompilationFailure               NativeMemoryUsage
 CompilerConfiguration (1)        NativeMemoryUsageTotal
 CompilerInlining                 NativeMethodSample (21741)
 CompilerPhase                    NetworkUtilization (86)
 CompilerQueueUtilization (43)    OSInformation (1)
 CompilerStatistics (438)         ObjectAllocationInNewTLAB
 ConcurrentModeFailure            ObjectAllocationOutsideTLAB
 ContainerCPUThrottling           ObjectAllocationSample (1960)
 ContainerCPUUsage                ObjectCount
 ContainerConfiguration           ObjectCountAfterGC
 Container

查看网络使用情况

PS \openjdk-25> jcmd 1240 JFR.view NetworkUtilization
1240:

                              Network Utilization

Time     Network Interface                                 Read Rate Write Rate
-------- ------------------------------------------------ ---------- ----------
11:03:10 Intel(R) Dual Band Wireless-AC 3165                1.4 kbps   1.9 kbps
11:03:16 Intel(R) Dual Band Wireless-AC 3165                1.3 kbps   1.6 kbps
11:03:21 Intel(R) Dual Band Wireless-AC 3165               75.8 kbps  76.0 kbps
11:13:03 Intel(R) Dual Band Wireless-AC 3165                   0 bps    472 bps
11:13:09 Intel(R) Dual Band Wireless-AC 3165                 216 bps   1.2 kbps
...

Timespan: 11:03:10 - 11:13:10

指定事件具体名称

指定以jdk.开头的事件，例：jdk.ThreadSleep。

各类事件名称可以查看jdk/lib/jfr下的default.jfc或profile.jfc，若启动JFR时未指定settings，则默认使用的default.jfc。

PS \openjdk-25> jcmd 1240 JFR.view jdk.ThreadSleep
1240:

                                     Java Thread Sleep

Start Time Duration Event Thread Stack Trace                                     Sleep Time
---------- -------- ------------ ----------------------------------------------- ----------
11:14:46     10.4 s container-0  org.apache.catalina.core.StandardServer.await()     10.0 s
11:14:56     10.4 s container-0  org.apache.catalina.core.StandardServer.await()     10.0 s
11:15:07     10.4 s container-0  org.apache.catalina.core.StandardServer.await()     10.0 s
...

Timespan: 11:05:27 - 11:15:27

jfr

jdk中自带的jfr view和jcmd命令的JFR.view使用基本相同，jfr命令主要查看dump出来的.jfr离线文件。

参考链接

https://inside.java/2023/05/31/jfr-view-command/

https://egahlin.github.io/2023/05/30/views.html