K8S增加限制后的启动时间验证

背景

前段时间看了下JVM载linux上面的启动时间, 进行过一些验证. 
最近想着能够验证一下K8S上面的启动相关的信息
所以就整理了一下. 
虽然没有特别好的结论,
但是还是发现自己对JVM的启动和参数还是了解的不够深入. 

自己的几个启动参数

1. "-XX:MaxRAMPercentage=80.0","-XX:MinRAMPercentage=50.0"
2. "-XX:-UseAdaptiveSizePolicy","-XX:MaxRAMPercentage=80.0","-XX:MinRAMPercentage=50.0"
3. "-XX:-UseAdaptiveSizePolicy","-XX:InitialRAMPercentage=75.0","-XX:MaxRAMPercentage=75.0","-XX:MinRAMPercentage=75.0"
4. "-XX:InitialRAMPercentage=75.0","-XX:MaxRAMPercentage=75.0","-XX:MinRAMPercentage=75.0","-XX:SurvivorRatio=3","-XX:NewRatio=1",

启动脚本挨个说明

启动顺序的排序为: 
4 3 1 2 
详细信息为: 
4. 最快, 怀疑启动过程中, 需要消耗最多的young区域.  old区域可以不用非常大. 所以比较适合启动. 
3. 次之, 与4的启动速度相差无几, 所以感觉方式3 应该是比较好的启动方式. 
1. 再次之, 慢大约 5%左右, 其实差异性不是很大, 但是堆区大小有一些差异. 
2. 最慢, 堆没有设置初始堆大小, 最大最小堆不一样, 然后还关闭了 自适应堆区设置, 导致启动速度很慢, 90min都没有启动起来. 
   堆区显示也只有1G左右, 所以几乎不可用. 

关于堆区的显示问题

进入容器后可以使用jmap -heap 1 的方式进行查看. 
New Generation (Eden + 1 Survivor Space):
   capacity = 9709027328 (9259.25MB)
Eden Space:
   capacity = 7281836032 (6944.5MB)
From Space:
   capacity = 2427191296 (2314.75MB)
To Space:
   capacity = 2427191296 (2314.75MB)
tenured generation:
   capacity = 12136218624 (11574.0MB)

注意这个设置的是 : 
"-XX:SurvivorRatio=3","-XX:NewRatio=1"

关于开启UseAdaptiveSizePolicy的情况

内存启动过程中 堆区变化是很大的
一开始: 
Heap Configuration:
   MinHeapFreeRatio         = 0
   MaxHeapFreeRatio         = 100
   MaxHeapSize              = 24052236288 (22938.0MB)
   NewSize                  = 156237824 (149.0MB)
   MaxNewSize               = 8017412096 (7646.0MB)
   OldSize                  = 313524224 (299.0MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

三分钟后
Heap Configuration:
   MinHeapFreeRatio         = 0
   MaxHeapFreeRatio         = 100
   MaxHeapSize              = 24052236288 (22938.0MB)
   NewSize                  = 156237824 (149.0MB)
   MaxNewSize               = 8017412096 (7646.0MB)
   OldSize                  = 313524224 (299.0MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

关于资源限制

        resources:
          limits:
            cpu: 6
            memory: 28Gi
          requests:
            cpu: 6
            memory: 28Gi