Java GC日誌中的「375848K-> 125488K（4355072K）」是什麼意思？

Question

我的Java GC日誌：

[GC (Allocation Failure) [PSYoungGen: 267611K->5387K(255488K)] 386801K->125992K(4367872K), 0.0187757 secs] [Times: user=0.05 sys=0.01, real=0.02 secs] 
[GC (Allocation Failure) [PSYoungGen: 255243K->4819K(242688K)] 375848K->125488K(4355072K), 0.0157165 secs] [Times: user=0.05 sys=0.00, real=0.02 secs] 
2015-10-16 16:30:53.623 INFO 26072 ---  [  Thread-2] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@5194569f: startup date [Fri Oct 16 13:57:40 CST 2015]; root of context hierarchy 
2015-10-16 16:30:53.628 INFO 26072 ---  [  Thread-4] c.e.c.s.c.l.EnniuWeightedLoadBalancer : Shutting down the Executor Pool for DynamicServerListLoadBalancer 
2015-10-16 16:30:53.629 INFO 26072 ---  [  Thread-2] ationConfigEmbeddedWebApplicationContext : Closing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@63510626: startup date [Fri Oct 16 13:57:44 CST 2015]; parent: org.springframework.context.annotation.AnnotationConfigApplicationContext@5194569f 
2015-10-16 16:30:53.635 INFO 26072 ---  [  Thread-2] o.s.c.support.DefaultLifecycleProcessor : Stopping beans in phase 0 
2015-10-16 16:30:53.648 INFO 26072 ---  [  Thread-2] o.s.j.e.a.AnnotationMBeanExporter  : Unregistering JMX-exposed beans on shutdown 
2015-10-16 16:30:53.649 INFO 26072 ---  [  Thread-2] o.s.j.e.a.AnnotationMBeanExporter  : Unregistering JMX-exposed beans 
Heap 
PSYoungGen  total 242688K, used 100212K [0x0000000742800000, 0x000000075bf80000, 0x00000007c0000000) 
    eden space 237568K, 40% used [0x0000000742800000,0x0000000748528590,0x0000000751000000) 
    from space 5120K, 94% used [0x000000075ba80000,0x000000075bf34d70,0x000000075bf80000) 
    to space 20992K, 0% used [0x0000000759680000,0x0000000759680000,0x000000075ab00000) 
ParOldGen  total 4112384K, used 120668K [0x0000000647800000, 0x0000000742800000, 0x0000000742800000) 
    object space 4112384K, 2% used [0x0000000647800000,0x000000064edd72f0,0x0000000742800000) 
Metaspace  used 71725K, capacity 76019K, committed 76248K, reserved 1114112K 
    class space used 9925K, capacity 10922K, committed 10968K, reserved 1048576K 

那麼，是什麼PSYoungGen: 267611K->5387K(255488K)是什麼意思？

Answer 1

這意味着年輕的gen的規模從267米減少到5米，節省255米的RAM空間。

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