java 启动参数 -XX:+PrintHeapAtGC
在启动时, 加入 -XX:+PrintHeapAtGC 将会看到如下log 打印
{Heap before GC invocations=4 (full 0):
PSYoungGen total 17408K, used 17392K [0x00000000fdf00000, 0x0000000100000000, 0x0000000100000000)
eden space 16384K, 100% used [0x00000000fdf00000,0x00000000fef00000,0x00000000fef00000)
from space 1024K, 98% used [0x00000000fef00000,0x00000000feffc010,0x00000000ff000000)
to space 1024K, 0% used [0x00000000fff00000,0x00000000fff00000,0x0000000100000000)
ParOldGen total 68608K, used 34096K [0x00000000f9c00000, 0x00000000fdf00000, 0x00000000fdf00000)
object space 68608K, 49% used [0x00000000f9c00000,0x00000000fbd4c000,0x00000000fdf00000)
Metaspace used 2612K, capacity 4486K, committed 4864K, reserved 1056768K
class space used 285K, capacity 386K, committed 512K, reserved 1048576K
[GC (Allocation Failure) [PSYoungGen: 17392K->1024K(32768K)] 51488K->52816K(101376K), 0.0101398 secs] [Times: user=0.00 sys=0.00, real=0.00
Heap after GC invocations=4 (full 0):
PSYoungGen total 32768K, used 1024K [0x00000000fdf00000, 0x0000000100000000, 0x0000000100000000)
eden space 31744K, 0% used [0x00000000fdf00000,0x00000000fdf00000,0x00000000ffe00000)
from space 1024K, 100% used [0x00000000fff00000,0x0000000100000000,0x0000000100000000)
to space 1024K, 0% used [0x00000000ffe00000,0x00000000ffe00000,0x00000000fff00000)
ParOldGen total 68608K, used 51792K [0x00000000f9c00000, 0x00000000fdf00000, 0x00000000fdf00000)
object space 68608K, 75% used [0x00000000f9c00000,0x00000000fce94050,0x00000000fdf00000)
Metaspace used 2612K, capacity 4486K, committed 4864K, reserved 1056768K
class space used 285K, capacity 386K, committed 512K, reserved 1048576K
}