那些遇到过的问题

为什么我在增加内存时会更频繁地获得GC？

Son*_*key 7 java garbage-collection g1gc

我有一个关于g1gc的问题。

在此处输入图片说明

在此处输入图片说明

这些是堆使用情况图。

上面是-Xms4g -Xmx4g。
底部是-Xms8g -Xmx8g。

我不知道为什么8g选项会导致g1gc发生更多。其他选项均为默认设置。

服务器规范是40个逻辑过程。

ps。有哪些适当的调优选项？

附加问题

内存分配越大->区域大小越大，内存分配能否更快？

gc.log

4G gc.log

2019-05-07T21:03:42.093+0900: 10.280: [GC pause (G1 Evacuation Pause) (young), 0.1785373 secs]
   [Parallel Time: 43.4 ms, GC Workers: 28]
      [GC Worker Start (ms): Min: 10280.0, Avg: 10280.1, Max: 10280.6, Diff: 0.6]
      [Ext Root Scanning (ms): Min: 0.0, Avg: 0.4, Max: 0.8, Diff: 0.8, Sum: 12.0]
      [Update RS (ms): Min: 0.8, Avg: 1.1, Max: 1.6, Diff: 0.8, Sum: 31.5]
         [Processed Buffers: Min: 0, Avg: 2.0, Max: 3, Diff: 3, Sum: 56]
      [Scan RS (ms): Min: 0.0, Avg: 0.4, Max: 0.7, Diff: 0.7, Sum: 10.9]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Object Copy (ms): Min: 38.0, Avg: 38.5, Max: 39.9, Diff: 1.9, Sum: 1079.0]
      [Termination (ms): Min: 1.3, Avg: 2.6, Max: 3.2, Diff: 1.9, Sum: 74.1]
         [Termination Attempts: Min: 413, Avg: 769.6, Max: 855, Diff: 442, Sum: 21549]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.1, Sum: 2.0]
      [GC Worker Total (ms): Min: 42.7, Avg: 43.2, Max: 43.4, Diff: 0.7, Sum: 1209.5]
      [GC Worker End (ms): Min: 10323.3, Avg: 10323.3, Max: 10323.4, Diff: 0.1]
   [Code Root Fixup: 0.0 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.4 ms]
   [Other: 134.7 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 132.4 ms]
      [Ref Enq: 0.9 ms]
      [Redirty Cards: 0.3 ms]
      [Humongous Register: 0.1 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 0.7 ms]
   [Eden: 928.0M(928.0M)->0.0B(828.0M) Survivors: 26.0M->120.0M Heap: 1193.0M(4096.0M)->409.0M(4096.0M)]
Heap after GC invocations=8 (full 0):
 garbage-first heap   total 4194304K, used 418816K [0x00000006c0000000, 0x00000006c0204000, 0x00000007c0000000)
  region size 2048K, 60 young (122880K), 60 survivors (122880K)
 Metaspace       used 28525K, capacity 30824K, committed 31104K, reserved 1077248K
  class space    used 3583K, capacity 4166K, committed 4224K, reserved 1048576K
}
 [Times: user=1.21 sys=0.08, real=0.18 secs]
{Heap before GC invocations=8 (full 0):
 garbage-first heap   total 4194304K, used 744448K [0x00000006c0000000, 0x00000006c0204000, 0x00000007c0000000)
  region size 2048K, 219 young (448512K), 60 survivors (122880K)
 Metaspace       used 28525K, capacity 30824K, committed 31104K, reserved 1077248K
  class space    used 3583K, capacity 4166K, committed 4224K, reserved 1048576K
2019-05-07T21:03:42.895+0900: 11.082: [GC pause (G1 Evacuation Pause) (young), 0.0505563 secs]
   [Parallel Time: 11.6 ms, GC Workers: 28]
      [GC Worker Start (ms): Min: 11082.3, Avg: 11082.6, Max: 11083.6, Diff: 1.3]
      [Ext Root Scanning (ms): Min: 0.0, Avg: 0.4, Max: 0.8, Diff: 0.8, Sum: 9.9]
      [Update RS (ms): Min: 0.4, Avg: 1.0, Max: 1.5, Diff: 1.1, Sum: 29.4]
         [Processed Buffers: Min: 1, Avg: 1.8, Max: 3, Diff: 2, Sum: 50]
      [Scan RS (ms): Min: 0.8, Avg: 1.2, Max: 1.4, Diff: 0.6, Sum: 32.4]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Object Copy (ms): Min: 8.3, Avg: 8.4, Max: 8.6, Diff: 0.2, Sum: 236.3]
      [Termination (ms): Min: 0.0, Avg: 0.1, Max: 0.1, Diff: 0.1, Sum: 2.8]
         [Termination Attempts: Min: 1, Avg: 42.7, Max: 52, Diff: 51, Sum: 1195]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.1, Sum: 2.0]
      [GC Worker Total (ms): Min: 10.2, Avg: 11.2, Max: 11.5, Diff: 1.3, Sum: 312.9]
      [GC Worker End (ms): Min: 11093.7, Avg: 11093.8, Max: 11093.8, Diff: 0.1]
   [Code Root Fixup: 0.0 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.3 ms]
   [Other: 38.6 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 37.0 ms]
      [Ref Enq: 0.5 ms]
      [Redirty Cards: 0.3 ms]
      [Humongous Register: 0.1 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 0.5 ms]
   [Eden: 318.0M(252.0M)->0.0B(1052.0M) Survivors: 120.0M->48.0M Heap: 727.0M(4096.0M)->397.0M(4096.0M)]
Heap after GC invocations=9 (full 0):
 garbage-first heap   total 4194304K, used 406528K [0x00000006c0000000, 0x00000006c0204000, 0x00000007c0000000)
  region size 2048K, 24 young (49152K), 24 survivors (49152K)
 Metaspace       used 28525K, capacity 30824K, committed 31104K, reserved 1077248K
  class space    used 3583K, capacity 4166K, committed 4224K, reserved 1048576K
}
 [Times: user=0.34 sys=0.02, real=0.05 secs]
{Heap before GC invocations=9 (full 0):
 garbage-first heap   total 4194304K, used 912384K [0x00000006c0000000, 0x00000006c0204000, 0x00000007c0000000)
  region size 2048K, 271 young (555008K), 24 survivors (49152K)
 Metaspace       used 29461K, capacity 31868K, committed 32256K, reserved 1077248K
  class space    used 3681K, capacity 4237K, committed 4352K, reserved 1048576K
Run Code Online (Sandbox Code Playgroud)

8G gc.log

2019-05-05T02:39:16.996+0900: 201016.724: [GC pause (G1 Evacuation Pause) (young), 0.0336675 secs]
   [Parallel Time: 12.9 ms, GC Workers: 28]
      [GC Worker Start (ms): Min: 201016724.7, Avg: 201016724.9, Max: 201016725.0, Diff: 0.2]
      [Ext Root Scanning (ms): Min: 0.8, Avg: 1.2, Max: 5.2, Diff: 4.4, Sum: 32.4]
      [Update RS (ms): Min: 0.0, Avg: 3.1, Max: 3.5, Diff: 3.5, Sum: 87.7]
         [Processed Buffers: Min: 0, Avg: 11.1, Max: 30, Diff: 30, Sum: 310]
      [Scan RS (ms): Min: 0.1, Avg: 0.3, Max: 0.3, Diff: 0.2, Sum: 7.3]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [Object Copy (ms): Min: 6.9, Avg: 7.5, Max: 7.7, Diff: 0.8, Sum: 211.2]
      [Termination (ms): Min: 0.2, Avg: 0.3, Max: 0.4, Diff: 0.2, Sum: 9.0]
         [Termination Attempts: Min: 105, Avg: 124.7, Max: 146, Diff: 41, Sum: 3491]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 3.2]
      [GC Worker Total (ms): Min: 12.4, Avg: 12.5, Max: 12.7, Diff: 0.4, Sum: 350.8]
      [GC Worker End (ms): Min: 201016737.3, Avg: 201016737.4, Max: 201016737.5, Diff: 0.2]
   [Code Root Fixup: 0.0 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.7 ms]
   [Other: 20.0 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 17.2 ms]
      [Ref Enq: 0.2 ms]
      [Redirty Cards: 0.3 ms]
      [Humongous Register: 0.1 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 1.7 ms]
   [Eden: 4864.0M(4864.0M)->0.0B(4868.0M) Survivors: 48.0M->44.0M Heap: 5968.1M(8192.0M)->1091.2M(8192.0M)]
Heap after GC invocations=19405 (full 0):
 garbage-first heap   total 8388608K, used 1117388K [0x00000005c0000000, 0x00000005c0404000, 0x00000007c0000000)
  region size 4096K, 11 young (45056K), 11 survivors (45056K)
 Metaspace       used 187853K, capacity 205120K, committed 210176K, reserved 1232896K
  class space    used 22574K, capacity 25471K, committed 26368K, reserved 1048576K
}
 [Times: user=0.39 sys=0.00, real=0.04 secs]
{Heap before GC invocations=19405 (full 0):
 garbage-first heap   total 8388608K, used 6106497K [0x00000005c0000000, 0x00000005c0404000, 0x00000007c0000000)
  region size 4096K, 1228 young (5029888K), 11 survivors (45056K)
 Metaspace       used 187853K, capacity 205120K, committed 210176K, reserved 1232896K
  class space    used 22574K, capacity 25471K, committed 26368K, reserved 1048576K
2019-05-05T02:39:33.830+0900: 201033.558: [GC pause (G1 Evacuation Pause) (young), 0.0373282 secs]
2019-05-05T02:39:33.830+0900: 201033.558: [GC pause (G1 Evacuation Pause) (young), 0.0373282 secs]
   [Parallel Time: 13.9 ms, GC Workers: 28]
      [GC Worker Start (ms): Min: 201033558.4, Avg: 201033558.5, Max: 201033558.6, Diff: 0.2]
      [Ext Root Scanning (ms): Min: 0.8, Avg: 1.2, Max: 4.5, Diff: 3.7, Sum: 32.5]
      [Update RS (ms): Min: 0.0, Avg: 2.8, Max: 3.1, Diff: 3.1, Sum: 77.4]
         [Processed Buffers: Min: 0, Avg: 10.3, Max: 31, Diff: 31, Sum: 289]
      [Scan RS (ms): Min: 0.1, Avg: 0.3, Max: 0.3, Diff: 0.3, Sum: 7.1]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [Object Copy (ms): Min: 8.5, Avg: 8.8, Max: 8.9, Diff: 0.4, Sum: 246.0]
      [Termination (ms): Min: 0.3, Avg: 0.4, Max: 0.5, Diff: 0.2, Sum: 12.0]
         [Termination Attempts: Min: 135, Avg: 156.5, Max: 175, Diff: 40, Sum: 4382]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 3.3]
      [GC Worker Total (ms): Min: 13.3, Avg: 13.5, Max: 13.7, Diff: 0.3, Sum: 378.4]
      [GC Worker End (ms): Min: 201033571.9, Avg: 201033572.0, Max: 201033572.1, Diff: 0.2]
   [Code Root Fixup: 0.0 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.8 ms]
   [Other: 22.6 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 18.5 ms]
      [Ref Enq: 0.3 ms]
      [Redirty Cards: 1.0 ms]
      [Humongous Register: 0.1 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 2.1 ms]
   [Eden: 4868.0M(4868.0M)->0.0B(4880.0M) Survivors: 44.0M->32.0M Heap: 5963.4M(8192.0M)->1082.0M(8192.0M)]
Heap after GC invocations=19406 (full 0):
 garbage-first heap   total 8388608K, used 1107927K [0x00000005c0000000, 0x00000005c0404000, 0x00000007c0000000)
  region size 4096K, 8 young (32768K), 8 survivors (32768K)
 Metaspace       used 187853K, capacity 205120K, committed 210176K, reserved 1232896K
  class space    used 22574K, capacity 25471K, committed 26368K, reserved 1048576K
}
 [Times: user=0.41 sys=0.00, real=0.04 secs]
{Heap before GC invocations=19406 (full 0):
 garbage-first heap   total 8388608K, used 6122963K [0x00000005c0000000, 0x00000005c0404000, 0x00000007c0000000)
  region size 4096K, 1228 young (5029888K), 8 survivors (32768K)
 Metaspace       used 187853K, capacity 205120K, committed 210176K, reserved 1232896K
  class space    used 22574K, capacity 25471K, committed 26368K, reserved 1048576K
Run Code Online (Sandbox Code Playgroud)

Mad*_*lay 5

使用G1GC设置的JVM 将通过构造一个称为region的内存块来启动，而不会区分New / Survivor / Old物理内存。从逻辑上讲，有“新” /“幸存者” /“旧”，但实际上并没有按地址分开。

在任何区域中创建对象，并将对象的引用者信息存储在“记忆”集中（在整个堆中使用5％的级别）。记忆集是一种数据结构，可以轻松知道哪个区域分配了带有参考的对象。（将引用跟踪到该区域）

如果要创建一个大于区域大小的对象，它将在多个区域上创建一个对象，这组区域称为Humongous。此信息也存储在记忆集中。

区域大小可以从1 MB到32 MB不等，具体取决于堆大小。下表显示了如果未显式设置区域大小，则将基于最小堆大小选择区域大小。

|---------------------|------------------|
|    Min Heap Size    |   Region Size    |
|---------------------|------------------|
|     heap < 4GB      |       1MB        |
|---------------------|------------------|
|  4GB <= heap < 8GB  |       2MB        |
|---------------------|------------------|
|  8GB <= heap < 16GB |       4MB        |
|---------------------|------------------|
| 16GB <= heap < 32GB |       8MB        |
|---------------------|------------------|
| 32GB <= heap < 64GB |      16MB        |
|---------------------|------------------|
|     64GB < heap     |      32MB        |
|---------------------|------------------|
Run Code Online (Sandbox Code Playgroud)

因此，在您的情况下，区域的大小将以不同的方式计算。另外，内存分配模式可能会因您的应用程序而异。为了找到更准确的原因，我们需要一个垃圾收集日志。

您可以设置InitiatingheapOccupancyPercent为让后台线程开始计时。堆使用率与堆总大小的比率。减小该值可使您快速启动后台线程。默认值为45。但是，如果该值太小，则垃圾收集将运行得太频繁。它占用CPU周期，并且可能会影响应用程序本身的性能。

如您所知，电锯图是健康的应用程序。因此，即使不进行其他设置也没有大问题。

额外：错误报告可以帮助您解决问题

Bug-8151176中的描述是为了实际计算IHOP而计算旧发电占用/总堆大小

这意味着完全忽略了年轻一代的职业。也就是说，如果年轻一代的分数大于IHOP，则并发周期无法开始。

原因是，如果旧发电机的使用量超过当前堆容量的固定百分比，则会启动静态IHOP。如果用户或人体工程学认为旧的代不能大于触发并发标记的那部分堆容量，则标记将永远不会开始。

  • 非凡的答案！ (2认同)

归档时间：

查看次数：

206 次

最近记录：

7 年，5 月 前
相关归档
如何处理未经检查的投射警告？ 583
连接两个字节数组的简便方法 235
使用JavaBeans的地方？ 167
我可以从<filter-mapping>中的<url-pattern>中排除一些具体的URL吗？ 121
一遍又一遍地运行相同的junit测试的简单方法？ 112
如何将一个项目的spring-config.xml导入另一个项目的spring-config.xml？ 74
最终瞬态场和序列化 59
Java:Thread.interrupted()和Thread.isInterrupted()之间的使用差异？ 54
垃圾收集似乎关闭本地执行程序并导致RejectedExecutionException 4
会话中的垃圾收集将发生在PHP中与数据库管理会话时？ 0
难疑归档
Bash中的Echo newline打印文字\n 2171
如何在Java中拆分字符串 1564
何时使用struct？ 1347
在JavaScript中停止setInterval调用 1332
如何从Git的暂存区域中删除单个文件,但不将其从索引中删除或撤消对文件本身的更改？ 1177
我是否提交了由npm 5创建的package-lock.json文件？ 1164
如何将参数传递给批处理文件？ 1100
按属性排序自定义对象的ArrayList 1093
angular-route和angular-ui-router之间有什么区别？ 1064
错误消息"未找到与约束合同名称匹配的导出" 1057