线上排查：新生代老年代比例错误问题#

起因#

线上一个应用频繁full gc，排查发现单pod总内存3g的情况下新生代只有200mb，很奇怪，于是到容器里查看jvm参数。

jamp -heap 1，打印

1
Heap Configuration:
2
   MinHeapFreeRatio         = 40
3
   MaxHeapFreeRatio         = 70
4
   MaxHeapSize              = 3221225472 (3072.0MB)
5
   NewSize                  = 261685248 (249.5625MB)
6
   MaxNewSize               = 261685248 (249.5625MB)
7
   OldSize                  = 2959540224 (2822.4375MB)
8
   NewRatio                 = 2
9
   SurvivorRatio            = 8
10
   MetaspaceSize            = 268435456 (256.0MB)
11
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
12
   MaxMetaspaceSize         = 268435456 (256.0MB)
13
   G1HeapRegionSize         = 0 (0.0MB)
14

15
Heap Usage:
16
New Generation (Eden + 1 Survivor Space):
17
   capacity = 235536384 (224.625MB)
18
   used     = 45215760 (43.12110900878906MB)
19
   free     = 190320624 (181.50389099121094MB)
20
   19.19693222428005% used
21
Eden Space:
22
   capacity = 209387520 (199.6875MB)
23
   used     = 33745216 (32.18194580078125MB)
24
   free     = 175642304 (167.50555419921875MB)
25
   16.116154391627543% used
26
From Space:
27
   capacity = 26148864 (24.9375MB)
28
   used     = 11470544 (10.939163208007812MB)
29
   free     = 14678320 (13.998336791992188MB)
30
   43.866318628602755% used
31
To Space:
32
   capacity = 26148864 (24.9375MB)
33
   used     = 0 (0.0MB)
34
   free     = 26148864 (24.9375MB)
35
   0.0% used
36
concurrent mark-sweep generation:
37
   capacity = 2959540224 (2822.4375MB)
38
   used     = 279529808 (266.5803985595703MB)
39
   free     = 2680010416 (2555.8571014404297MB)
40
   9.445041690367646% used

NewRatio确实是2，但是新生代是224mb，老年代是2.8g，比例确实和监控一样，不符合默认的1:2配比

排查#

一番排查，google“NewRatio not work”后，发现一个JDK的bug： https://bugs.openjdk.org/browse/JDK-8153578

检查下JVM参数，确实使用了UseConcMarkSweepGC

解决#

在启动参数中指定新生代GC算法-XX:+UseParNewGC后，重新发布解决解决方式还可以在启动参数里指定-XXNewRatio=2解决，不过我们是用的指定新生代算法

乘桴

线上排查：新生代老年代比例错误问题#

起因#

排查#

解决#

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乘桴

线上排查：新生代老年代比例错误问题#

起因#

排查#

解决#

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