GC日志打印添加以及說明

項目經常自動重啟，但是沒有gc日志和dump文件。可以使用一下命令添加日志：

-XX:+PrintGCDetails -XX:+UseStringDeduplication -Xmx100M -XX:+UseG1GC -XX:+PrintGCTimeStamps -Xloggc:gc-%t.log -XX:+UseGCLogFileRotation -XX:GCLogFileSize=10M -XX:+HeapDumpAfterFullGC -XX:HeapDumpPath=e:\testDump

說明：

-XX:+PrintGCDetails 打印gc日志詳情，比如：

40.951: [GC pause (G1 Evacuation Pause) (young), 0.0031053 secs]
   [Parallel Time: 1.7 ms, GC Workers: 13]
      [GC Worker Start (ms): Min: 40951.5, Avg: 40951.6, Max: 40951.6, Diff: 0.1]
      [Ext Root Scanning (ms): Min: 0.3, Avg: 0.5, Max: 1.6, Diff: 1.2, Sum: 6.6]
      [Update RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
         [Processed Buffers: Min: 0, Avg: 0.2, Max: 1, Diff: 1, Sum: 2]
      [Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Object Copy (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.2]
      [Termination (ms): Min: 0.0, Avg: 1.0, Max: 1.1, Diff: 1.1, Sum: 13.0]
         [Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 13]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [GC Worker Total (ms): Min: 1.5, Avg: 1.5, Max: 1.6, Diff: 0.1, Sum: 20.0]
      [GC Worker End (ms): Min: 40953.1, Avg: 40953.1, Max: 40953.1, Diff: 0.0]
   [Code Root Fixup: 0.0 ms]
   [Code Root Purge: 0.0 ms]
   [String Dedup Fixup: 0.3 ms, GC Workers: 13]
      [Queue Fixup (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Table Fixup (ms): Min: 0.2, Avg: 0.2, Max: 0.3, Diff: 0.0, Sum: 3.1]
   [Clear CT: 0.1 ms]
   [Other: 1.0 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 0.9 ms]
      [Ref Enq: 0.0 ms]
      [Redirty Cards: 0.1 ms]
      [Humongous Register: 0.0 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 0.0 ms]
   [Eden: 0.0B(5120.0K)->0.0B(5120.0K) Survivors: 0.0B->0.0B Heap: 95.3M(100.0M)->95.3M(100.0M)]
 [Times: user=0.06 sys=0.00, real=0.00 secs]

eden區：回收前的內存（eden區總內存） ->回收后的內存(eden區總內存) Survivors：回收前內存->回收后內存堆區: 回收前內存(堆總內存) ->回收后內存（堆總內存）

-XX:+UseG1G -XX:+UseStringDeduplication

Note 1：要想使用此功能，你需要把你的Java升級到Java 8 update 20以及往后的版本。

Note 2：“ -XX:+UseStringDeduplication” 參數是運行在G1之上的，所以你需要在G1下使用此參數才會生效。

這個網上看是說能節省內存，可是自己使用profile比對，發現除了減少了一部分內存，full GC的次數大大減少了。附上自己的截圖：

-XX:+PrintGCDetails -Xmx100M -XX:+UseG1GC -Xloggc:gc-%t.log -XX:+UseGCLogFileRotation -XX:GCLogFileSize=10M -XX:+HeapDumpAfterFullGC -XX:HeapDumpPath=e:\testDump

-XX:+PrintGCDetails -Xmx100M -XX:+UseG1GC -XX:+UseStringDeduplication -Xloggc:gc-%t.log -XX:+UseGCLogFileRotation -XX:GCLogFileSize=10M -XX:+HeapDumpAfterFullGC -XX:HeapDumpPath=e:\testDump

-Xloggc:gc-%t.log :GC日志文件名稱

-XX:GCLogFileSize=10M 日志文件大小

-XX:+HeapDumpAfterFullGC fullgc前dump文件保存

-XX:HeapDumpPath=e:\testDump dump文件保存路徑

-XX:+PrintGCTimeStamps 輸出GC的時間戳（以基準時間的形式）

-XX:+PrintGCDateStamps 輸出GC的時間戳（以日期的形式，如 2023-05-04T21:53:59.234+0800）

posted @ 2022-11-15 11:45 Doyourself! 閱讀(1041) 評論(0) 收藏舉報

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GC日志打印添加以及說明

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