云计算GC日志解析

概念：
	Serial收集器中新生代的名称：DefNew (Default New Generation)
	ParNew收集器中新生代的名称：ParNew (Parallel New Generation)
	Parallel Scavenge收集器中新生代的名称：PSYoungGen


GC日志分析：
	[GC[ParNew: 2771276K->313122K(2831168K), 0.3010830 secs] 4183496K->1794522K(8074048K), 0.3011690 secs] [Times: user=1.01 sys=0.16, real=0.30 secs]
	GC								Young GC
	ParNew							新生代使用ParNew收集器
	2771276K->313122K(2831168K)		gc前新生代已使用的容量->gc后新生代已使用容量(新生代的总容量)
	4183496K->1794522K(8074048K)	gc前java堆已使用的容量->gc后java堆已使用容量(新生代的总容量)
	0.3010830 secs					新生代gc花费的时间
	0.3011690 secs					java堆gc花费的时间
	user	用户态消耗的CPU时间
	sys		内核态消耗的CPU时间
	real 	操作从开始到结束所经过的墙钟时间
				1>墙钟时间包括CPU时间、各种非运算的等待耗时:等待磁盘I/O、线程阻塞等。
				2>当系统是多CPU或多核的话，多线程操作会叠加这些CPU时间，故我们经常可以看到user或sys大于real的情况。
	

举例：

	17339682 [GC[ParNew: 2771276K->313122K(2831168K), 0.3010830 secs] 4183496K->1794522K(8074048K), 0.3011690 secs] [Times: user=1.01 sys=0.16, real=0.30 secs]
	17339683 [GC[ParNew: 2829730K->314560K(2831168K), 0.2366420 secs] 4311130K->1882659K(8074048K), 0.2367140 secs] [Times: user=1.18 sys=0.02, real=0.24 secs]
	17339684 [GC[ParNew: 2831168K->314560K(2831168K), 0.5052540 secs] 4399267K->2046532K(8074048K), 0.5053260 secs] [Times: user=1.51 sys=0.30, real=0.51 secs]
	17339685 [GC[ParNew: 2831168K->314560K(2831168K), 0.2661690 secs] 4563140K->2161862K(8074048K), 0.2662570 secs] [Times: user=1.29 sys=0.02, real=0.26 secs]


	17339692 [GC [1 CMS-initial-mark: 2676020K(5242880K)] 3015776K(8074048K), 0.2355140 secs] [Times: user=0.21 sys=0.03, real=0.23 secs]

	17339695 [CMS-concurrent-mark: 2.344/3.052 secs] [Times: user=12.18 sys=0.28, real=3.05 secs]


	17339696 [CMS-concurrent-preclean: 0.359/0.359 secs] [Times: user=1.07 sys=0.00, real=0.36 secs]

	17339699 [CMS-concurrent-abortable-preclean: 1.295/2.062 secs] [Times: user=6.77 sys=0.35, real=2.07 secs]

	17339700 [GC[YG occupancy: 819967 K (2831168 K)][Rescan (parallel) , 0.1143590 secs][weak refs processing, 0.0011090 secs][scrub string table, 0.0016320 secs] [1 CMS-remark: 3178137K(5242880K)] 3998104K(8074048         K), 0.1173070 secs] [Times: user=0.68 sys=0.00, real=0.11 secs]

	17339702 [CMS-concurrent-sweep: 1.496/1.752 secs] [Times: user=5.87 sys=0.00, real=1.75 secs]
	17339703 [CMS-concurrent-reset: 0.039/0.039 secs] [Times: user=0.11 sys=0.00, real=0.04 secs]

	17339713 [GC [1 CMS-initial-mark: 3805421K(5242880K)] 4170491K(8074048K), 0.2260330 secs] [Times: user=0.23 sys=0.00, real=0.22 secs]

	17339731 [GC[ParNew: 2831168K->2831168K(2831168K), 0.0000320 secs][CMS[CMS-concurrent-mark: 4.525/6.195 secs] [Times: user=21.57 sys=1.04, real=6.19 secs]

	17339732  (concurrent mode failure): 5105678K->5242879K(5242880K), 14.1941150 secs] 7936846K->5418601K(8074048K), [CMS Perm : 65531K->65391K(131072K)], 14.1942500 secs] [Times: user=14.42 sys=0.23, real=14.19 s         ecs]
	17339733 [GC [1 CMS-initial-mark: 5242879K(5242880K)] 8012667K(8074048K), 1.2654450 secs] [Times: user=1.26 sys=0.00, real=1.26 secs]
	17339734 [Full GC[CMS[CMS-concurrent-mark: 4.458/4.459 secs] [Times: user=9.35 sys=0.01, real=4.46 secs]
	17339735  (concurrent mode failure): 5242879K->5242879K(5242880K), 17.7646400 secs] 8074042K->5555551K(8074048K), [CMS Perm : 65391K->65391K(131072K)], 17.7647310 secs] [Times: user=21.95 sys=0.00, real=17.76 s         ecs]
	17339736 [GC [1 CMS-initial-mark: 5242879K(5242880K)] 8048767K(8074048K), 1.3574940 secs] [Times: user=1.36 sys=0.00, real=1.36 secs]
	17339737 [Full GC[CMS[CMS-concurrent-mark: 4.408/4.409 secs] [Times: user=8.97 sys=0.00, real=4.41 secs]
	17339738  (concurrent mode failure): 5242879K->5242879K(5242880K), 18.0209010 secs] 8074047K->5682979K(8074048K), [CMS Perm : 65391K->65391K(131072K)], 18.0209880 secs] [Times: user=22.28 sys=0.00, real=18.02 s         ecs]

	17339900 [GC [1 CMS-initial-mark: 5242880K(5242880K)] 8029020K(8074048K), 2.6830200 secs] [Times: user=2.68 sys=0.00, real=2.69 secs] 17339901 [Full GC[CMS[CMS-concurrent-mark: 4.176/4.177 secs] [Times: user=8.56 sys=0.00, real=4.17 secs]
	17339902  (concurrent mode failure): 5242880K->5242880K(5242880K), 19.8391610 secs] 8074047K->8031137K(8074048K), [CMS Perm : 65199K->65199K(131072K)], 19.8392250 secs] [Times: user=23.89 sys=0.00, real=19.83 s         ecs] 
	17339903 [Full GC[CMS: 5242880K->5242880K(5242880K), 18.7585490 secs] 8074040K->8033385K(8074048K), [CMS Perm : 65199K->65199K(131072K)], 18.7586190 secs] [Times: user=18.74 sys=0.00, real=18.76 secs]
	17339904 [GC [1 CMS-initial-mark: 5242880K(5242880K)] 8033393K(8074048K), 2.6797130 secs] [Times: user=2.68 sys=0.00, real=2.68 secs] 17339905 [Full GC[CMS[CMS-concurrent-mark: 4.171/4.172 secs] [Times: user=8.53 sys=0.00, real=4.17 secs]
	17339906  (concurrent mode failure): 5242880K->5242879K(5242880K), 22.9767690 secs] 8074047K->8035243K(8074048K), [CMS Perm : 65199K->65199K(131072K)], 22.9768360 secs] [Times: user=27.03 sys=0.00, real=22.97 s         ecs]