数：-Xmx1024m
-Xms1024m
-XX:MaxPermSize=512m
-XX:PermSize=512m
-XX:ReservedCodeCacheSize=64m
  这段gc日志是什么原因，刚开始还比较正常，过了一会以后就一直执行full gc 而且感觉完全没有被回收


246.903: [GC 246.903: [DefNew: 419456K->52416K(471872K), 0.1968420 secs] 419456K->65324K(996160K), 0.1968960 secs] [Times: user=0.16 sys=0.03, real=0.20 secs]
260.883: [GC 260.883: [DefNew: 471872K->31465K(471872K), 0.1835558 secs] 484780K->96681K(996160K), 0.1835916 secs] [Times: user=0.17 sys=0.01, real=0.18 secs]
279.782: [GC 279.782: [DefNew: 450921K->26351K(471872K), 0.0988423 secs] 516137K->100883K(996160K), 0.0988873 secs] [Times: user=0.08 sys=0.02, real=0.10 secs]
336.299: [GC 336.299: [DefNew: 445807K->23405K(471872K), 0.1228503 secs] 520339K->115279K(996160K), 0.1228963 secs] [Times: user=0.13 sys=0.00, real=0.12 secs]
353.804: [GC 353.804: [DefNew: 442861K->26570K(471872K), 0.0518401 secs] 534735K->118443K(996160K), 0.0518858 secs] [Times: user=0.05 sys=0.00, real=0.05 secs]
369.930: [GC 369.930: [DefNew: 446026K->18654K(471872K), 0.0827542 secs] 537899K->129046K(996160K), 0.0828085 secs] [Times: user=0.08 sys=0.00, real=0.08 secs]
646.004: [Full GC (System) 646.004: [Tenured: 110391K->169046K(524288K), 0.5900779 secs] 387467K->169046K(996160K), [Perm : 92228K->92228K(524288K)], 0.5901298 secs] [Times: user=0.55 sys=0.02, real=0.59 secs]
757.403: [Full GC (System) 757.403: [Tenured: 169046K->174889K(524288K), 0.5257659 secs] 407134K->174889K(996160K), [Perm : 94157K->94157K(524288K)], 0.5258219 secs] [Times: user=0.52 sys=0.00, real=0.52 secs]
834.889: [Full GC (System) 834.889: [Tenured: 174889K->176155K(524288K), 0.5315415 secs] 460397K->176155K(996160K), [Perm : 94240K->94240K(524288K)], 0.5316011 secs] [Times: user=0.53 sys=0.00, real=0.53 secs]
894.902: [Full GC (System) 894.902: [Tenured: 176155K->160810K(524288K), 0.6421650 secs] 197688K->160810K(996160K), [Perm : 94240K->93666K(524288K)], 0.6422193 secs] [Times: user=0.64 sys=0.00, real=0.64 secs]
961.577: [Full GC (System) 961.577: [Tenured: 160810K->165913K(524288K), 0.4800967 secs] 264748K->165913K(996160K), [Perm : 94562K->94562K(524288K)], 0.4801460 secs] [Times: user=0.47 sys=0.00, real=0.48 secs]
1023.166: [Full GC (System) 1023.166: [Tenured: 165913K->167237K(524288K), 0.4560619 secs] 248002K->167237K(996160K), [Perm : 94577K->94577K(524288K)], 0.4561119 secs] [Times: user=0.45 sys=0.00, real=0.46 secs]
1100.885: [Full GC (System) 1100.885: [Tenured: 167237K->167838K(524288K), 0.4540202 secs] 203448K->167838K(996160K), [Perm : 94605K->94605K(524288K)], 0.4540702 secs] [Times: user=0.45 sys=0.00, real=0.45 secs]
1164.377:

日志里面的Full GC (System) 表示你的代码或者依赖的库里面使用了System.gc()的代码，
可以通过jvm加启动参数-XX:+DisableExplicitGC来禁止System.gc()的调用