- jmap -heap pid
查看java 堆（heap）使用情况
using thread-local object allocation.
Parallel GC with 4 thread(s) //GC 方式 Heap Configuration: //堆内存初始化配置
MinHeapFreeRatio=40 //对应jvm启动参数-XX:MinHeapFreeRatio设置JVM堆最小空闲比率(default 40)
1 2 | MaxHeapFreeRatio= 70 //对应jvm启动参数 -XX:MaxHeapFreeRatio设置JVM堆最大空闲比率(default 70) MaxHeapSize= 512 .0MB //对应jvm启动参数-XX:MaxHeapSize=设置JVM堆的最大大小 |
NewSize = 1.0MB //对应jvm启动参数-XX:NewSize=设置JVM堆的‘新生代’的默认大小
1 2 3 | MaxNewSize =4095MB //对应jvm启动参数-XX:MaxNewSize=设置JVM堆的‘新生代’的最大大小 OldSize = 4 .0MB //对应jvm启动参数-XX:OldSize=<value>:设置JVM堆的‘老生代’的大小 NewRatio = 8 //对应jvm启动参数-XX:NewRatio=:‘新生代’和‘老生代’的大小比率 |
SurvivorRatio = 8 //对应jvm启动参数-XX:SurvivorRatio=设置年轻代中Eden区与Survivor区的大小比值
1 | PermSize= 16 .0MB //对应jvm启动参数-XX:PermSize=<value>:设置JVM堆的‘永生代’的初始大小 |
MaxPermSize=64.0MB //对应jvm启动参数-XX:MaxPermSize= :设置JVM堆的‘永生代’的最大大小
Heap Usage: //堆内存分步
PS Young Generation
Eden Space: //Eden区内存分布
1 | capacity = 20381696 ( 19 .4375MB) //Eden区总容量 |
used = 20370032 (19.426376342773438MB) //Eden区已使用
1 | free = 11664 ( 0 .0111236572265625MB) //Eden区剩余容量 |
99.94277218147106% used //Eden区使用比率
From Space: //其中一个Survivor区的内存分布
1 2 3 | capacity = 8519680 ( 8 .125MB) used = 32768 ( 0 .03125MB) free = 8486912 ( 8 .09375MB) |
0.38461538461538464% used
To Space: //另一个Survivor区的内存分布
capacity = 9306112 (8.875MB)
used = 0 (0.0MB)
1 2 | free = 9306112 ( 8 .875MB) 0.0 % used |
PS Old Generation //当前的Old区内存分布
1 2 3 4 | capacity = 366280704 ( 349 .3125MB) used = 322179848 ( 307 .25464630126953MB) free = 44100856 ( 42 .05785369873047MB) 87.95982001825573 % used |
PS Perm Generation //当前的 “永生代” 内存分布
capacity = 32243712 (30.75MB)
used = 28918584 (27.57891082763672MB)
1 | free = 3325128 ( 3 .1710891723632812MB) |
89.68751488662348% used
- jmap -histo pid
查看堆内存(histogram)中的对象数量，大小
1 | num #instances #bytes class name |