JVM堆内存分析

jmap工具查看堆内存

jmap:全称JVM Memory Map

是一个可以输出所有内存中对象的工具，可以将JVM中的heap（堆），以二进制输出成文本，打印出Java进程对应的内存

找到pid

jmap -heap 19792

Attaching to process ID 19792, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.161-b12

using thread-local object allocation.
Parallel GC with 10 thread(s)

Heap Configuration:
   MinHeapFreeRatio         = 0                        ——>最小堆开放比率
   MaxHeapFreeRatio         = 100                      ——>最大堆开放比率
   MaxHeapSize              = 8537505792 (8142.0MB)    ——>新生代大小
   NewSize                  = 178257920 (170.0MB)      ——>最大新生代大小
   MaxNewSize               = 2845835264 (2714.0MB)    ——>年老代大小
   OldSize                  = 356515840 (340.0MB)      ——>最大年老代大小
   NewRatio                 = 2                        ——>新生代比率
   SurvivorRatio            = 8                        ——>存活比率
   MetaspaceSize            = 21807104 (20.796875MB)   ——>元空间大小
   CompressedClassSpaceSize = 1073741824 (1024.0MB)    ——>压缩类空间大小
   MaxMetaspaceSize         = 17592186044415 MB        ——>最大元空间大小
   G1HeapRegionSize         = 0 (0.0MB)                ——>G1堆区域大小

Heap Usage:
PS Young Generation
Eden Space:                                          ————>Eden空间
   capacity = 715128832 (682.0MB)                      ——>空间大小
   used     = 552720928 (527.1157531738281MB)          ——>使用
   free     = 162407904 (154.88424682617188MB)         ——>剩余
   77.28969987886043% used                             ——>比率
From Space:                                          ————>From空间
   capacity = 30408704 (29.0MB)                        ——>空间大小
   used     = 30395408 (28.987319946289062MB)          ——>使用
   free     = 13296 (0.0126800537109375MB)             ——>剩余
   99.95627567685884% used                             ——>比率
To Space:                                            ————>To空间
   capacity = 45088768 (43.0MB)                        ——>空间大小
   used     = 0 (0.0MB)                                ——>使用
   free     = 45088768 (43.0MB)                        ——>剩余
   0.0% used                                           ——>比率
PS Old Generation                                    ————>年老代
   capacity = 282066944 (269.0MB)                      ——>空间大小
   used     = 84960168 (81.02433013916016MB)           ——>使用
   free     = 197106776 (187.97566986083984MB)         ——>剩余
   30.1205688249666% used                              ——>比率

42326 interned Strings occupying 4345832 bytes.