-XX:NewSize=20m -XX:MaxNewSize=40m，-Xmn30m，-XX:NewRatio=5
这3组参数都可以影响年轻代的大小，混合使用的情况下，优先级是什么？
高优先级：
-XX:NewSize=20m -XX:MaxNewSize=40m
设置新生代初始值，最大值
中优先级：
-Xmn30m（默认等效-XX:NewSize=30m -XX:MaxNewSize=30m）
设置新生代初始值
低优先级：
-XX:NewRatio=5
设置老年代和新生代的比例。 例如：-XX:NewRatio = 4 → 新生代 ：老年代 = 1：4 ，即新生代占 1/5，老年代占 4/5
推荐使用 -Xmn参数，原因是这个参数相当于一次设定 NewSize/MaxNewSIze，而且两者相等，适用于生产环境；
-Xmn + -Xms + -Xmx 即可将堆内存布局完成
优先级验证
验证高优先级：
| 启动参数 |
|---|
-Xms60m -Xmx80m -Xmn30m -XX:NewSize=20m -XX:MaxNewSize=40m -XX:NewRatio=5 -XX:+PrintCommandLineFlags -Xlog:gc* |
| 启动日志 |
-XX:ConcGCThreads=3 -XX:G1ConcRefinementThreads=13 -XX:GCDrainStackTargetSize=64 -XX:InitialHeapSize=62914560 -XX:MarkStackSize=4194304 -XX:MaxHeapSize=83886080 -XX:MaxNewSize=41943040 -XX:MinHeapSize=62914560 -XX:NewRatio=5 -XX:NewSize=20971520 -XX:+PrintCommandLineFlags -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC -XX:-UseLargePagesIndividualAllocation[0.012s][warning][gc,ergo] -XX:NewSize and -XX:MaxNewSize override -XX:NewRatio |
| JPS+jhsdb jmap --heap --pid 进程ID |
| Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 83886080 (80.0MB) NewSize = 20971520 (20.0MB)MaxNewSize = 41943040 (40.0MB)OldSize = 5452592 (5.1999969482421875MB) NewRatio = 5 SurvivorRatio = 8 MetaspaceSize = 22020096 (21.0MB) CompressedClassSpaceSize = 1073741824 (1024.0MB) MaxMetaspaceSize = 17592186044415 MB G1HeapRegionSize = 1048576 (1.0MB) |
中优先级验证：
| 启动参数 |
|---|
-Xms60m -Xmx80m -Xmn30m -XX:NewRatio=5 -XX:+PrintCommandLineFlags -Xlog:gc* |
| 启动日志 |
-XX:ConcGCThreads=3 -XX:G1ConcRefinementThreads=13 -XX:GCDrainStackTargetSize=64 -XX:InitialHeapSize=62914560 -XX:MarkStackSize=4194304 -XX:MaxHeapSize=83886080 -XX:MaxNewSize=31457280 -XX:MinHeapSize=62914560 -XX:NewRatio=5 -XX:NewSize=31457280 -XX:+PrintCommandLineFlags -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC -XX:-UseLargePagesIndividualAllocation [0.015s][warning][gc,ergo] -XX:NewSize and -XX:MaxNewSize override -XX:NewRatio |
| JPS + jhsdb jmap --heap --pid 进程ID |
| Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 83886080 (80.0MB) NewSize = 31457280 (30.0MB)MaxNewSize = 31457280 (30.0MB)OldSize = 5452592 (5.1999969482421875MB) NewRatio = 5 SurvivorRatio = 8 MetaspaceSize = 22020096 (21.0MB) CompressedClassSpaceSize = 1073741824 (1024.0MB) MaxMetaspaceSize = 17592186044415 MB G1HeapRegionSize = 1048576 (1.0MB) |
低优先级验证：
| 启动参数 |
|---|
-Xms60m -Xmx80m -XX:NewRatio=5 -XX:+PrintCommandLineFlags -Xlog:gc* |
| 启动日志 |
-XX:ConcGCThreads=3 -XX:G1ConcRefinementThreads=13 -XX:GCDrainStackTargetSize=64 -XX:InitialHeapSize=62914560 -XX:MarkStackSize=4194304 -XX:MaxHeapSize=83886080 -XX:MinHeapSize=62914560 -XX:NewRatio=5 -XX:+PrintCommandLineFlags -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC -XX:-UseLargePagesIndividualAllocation |
| JPS + jhsdb jmap --heap --pid 进程ID |
| Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 83886080 (80.0MB) NewSize = 1363144 (1.2999954223632812MB)MaxNewSize = 13631488 (13.0MB) 因为新生代:老年代 = 1:5，且初始Heap Initial Capacity: 60M，所以这里为10MOldSize = 5452592 (5.1999969482421875MB)NewRatio = 5SurvivorRatio = 8 MetaspaceSize = 22020096 (21.0MB) CompressedClassSpaceSize = 1073741824 (1024.0MB) MaxMetaspaceSize = 17592186044415 MB G1HeapRegionSize = 1048576 (1.0MB) |
优先级验证（好早以前验证截图,删除可惜保留参考）
//JVM 启动参数
-Xms60m -Xmx80m -Xmn30m -XX:NewSize=20m -XX:MaxNewSize=40m -XX:NewRatio=5 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails//运行结果：
-XX:InitialHeapSize=62,914,560 -XX:MaxHeapSize=83,886,080
-XX:NewSize=20,971,520 -XX:MaxNewSize=41,943,040
-XX:NewRatio=5 -XX:+PrintCommandLineFlags -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC
------------------------------------------------------------------
//JVM 启动参数
-Xmx80m -Xms60m -Xmn30m -XX:NewRatio=5 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails//运行结果：
-XX:InitialHeapSize=62914560 -XX:MaxHeapSize=83886080
-XX:NewSize=31457280 -XX:MaxNewSize=31457280 -XX:NewRatio=5 -XX:+PrintCommandLineFlags -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC
------------------------------------------------------------------
//JVM 启动参数
-Xmx80m -Xms60m -XX:NewRatio=5 -XX:+PrintGCDetails -XX:+PrintCommandLineFlags//运行结果：
-XX:InitialHeapSize=62914560 -XX:MaxHeapSize=83886080
-XX:NewRatio=5 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC 
本文来自互联网用户投稿，文章观点仅代表作者本人，不代表本站立场，不承担相关法律责任。如若转载，请注明出处。 如若内容造成侵权/违法违规/事实不符，请点击【内容举报】进行投诉反馈！