微商城网站建设行情,网站建设捌金手指花总十八,廊坊seo关键词优化,北京网站制作设计推广公司目录
一、JVM Optimization
1、G1
1、G1内存模型
2、基础概念
3、G1特点#xff1a;
4、CMS日志分析
5、G1日志分析
2、GC参数
2.1、GC常用参数
2.2、Parallel常用参数
2.3、CMS常用参数
2.4、G1常用参数 一、JVM Optimization
1、G1
G1官网说明#xff1a;Gar…目录
一、JVM Optimization
1、G1
1、G1内存模型
2、基础概念
3、G1特点
4、CMS日志分析
5、G1日志分析
2、GC参数
2.1、GC常用参数
2.2、Parallel常用参数
2.3、CMS常用参数
2.4、G1常用参数 一、JVM Optimization
1、G1
G1官网说明Garbage First Garbage Collector Tuning
The Garbage First Garbage Collector (G1 GC) is the low-pause, server-style generational
garbage collector for Java HotSpot VM. The G1 GC uses concurrent and parallel phases
to achieve its target pause time and to maintain good throughput. When G1 GC determines
that a garbage collection is necessary, it collects the regions with the least live data
first (garbage first).
G1是Java HotSpot VM的低暂停、服务器端应用的垃圾收集器。G1 GC使用并行和并行阶段来实现其目标暂停
时间并保持良好的吞吐量。当G1GC确定有必要进行垃圾收集时它首先收集具有最少活动数据的区域
垃圾优先。G1是一种服务端应用使用的垃圾收集器目标是用在多核、大内存的机器上它在大多数情况下可以实现指定
的GC暂停时间同时还能保持较高的吞吐量。
分而治之分层模型
1、G1内存模型 humongous/hjuːˈmʌŋɡəs/ 巨大的、庞大的
humongous object超过单个region的50%
it collects the regions with the least live data first (garbage first).垃圾优先 每个分区都可能是年轻代也可能是老年代但是在同一时刻只能属于某个代。 年轻代、幸存区、老年代这些概念还存在成为逻辑上的概念这样方便复用之前分代框架的逻辑。在物理上不需要连续则带来了额外的好处——有的分区内垃圾对象特别多有的分区内垃圾对象很少G1会优先回收垃圾对象特别多的分区这样可以花费较少的时间来回收这些分区的垃圾这也就是G1名字的由来即首先收集垃圾最多的分区。 新生代其实并不是适用于这种算法的依然是在新生代满了的时候对整个新生代进行回收——整个新生代中的对象要么被回收、要么晋升至于新生代也采取分区机制的原因则是因为这样跟老年代的策略统一方便调整代的大小。 G1还是一种带压缩的收集器在回收老年代的分区时是将存活的对象从一个分区拷贝到另一个可用分区这个拷贝的过程就实现了局部的压缩。每个分区的大小从1M到32M不等但是都是2的幂次方。 2、基础概念 1、Card Table 由于做YGC时需要扫描整个OLD区(因为OLD区有可能有引用指向Y区)效率非常低所以JVM设计了CardTable 如果一个OLD区CardTable中有对象指向Y区就将它设为Dirty下次扫描时只需要扫描Dirty Card 在结构上Card Table用BitMap来实现。Dirty肮脏的脏数据 2、CSet Collection Set 一组可被回收的分区的集合。 在CSet中存活的数据会在GC过程中被移动到另一个可用分区CSet中的分区可以来自Eden空间、survivor空间、或者老年代。 CSet会占用不到整个堆空间的1%大小。 3、RSet RememberedSet (Remembered记得) 在Region中有一块区域记录了其他Region中的对象到本Region的引用 RSet的价值在于使得垃圾收集器不需要扫描整个堆找到谁引用了当前分区中的对象只需要扫描RSet即可。 4、RSet与赋值的效率 由于RSet 的存在那么每次给对象赋引用的时候就得做一些额外的操作指的是在RSet中做一些额外的记录在GC中被称为写屏障这个写屏障 不等于 内存屏障 5、GC何时触发 YGCEden空间不足、多线程并行执行 FGCOld空间不足、System.gc() 6、G1是否分代G1垃圾回收器会产生FGC吗 G1是逻辑分代物理不分代。会产生FGC,最后的对象分配不开了 7、如果G1产生FGC你应该做什么 1.扩内存 2. 提高CPU性能 3. 降低MixedGC触发的阈值让MixedGC提早发生默认是45% 8、G1中的MixedGC 1.CMS 2.XX:InitiatingHeapOccupacyPercent 默认值45%当O超过这个值时启动MixedGC 9、MixedGC的过程 1.初始标记 STW 2.并发标记 SATB算法 Snapshot At The Beginning GC开始时通过root tracing得到一个Snapshot 维持并发GC的正确性 如何做到并发GC的正确性三色标记算法 白对象没有标记标记阶段结束后会被回收 灰对象标记了但是他的Field还没有标记或标记完 黑对象标记了且他的Field也标记完成 漏标 在remark过程中黑色指向了白色如果不对黑色重新扫描则会漏标。会把白色D对象当做没有新引用指向从而回收掉。 并发标记过程中删除了所有从灰色到白色的引用会产生漏标此时白色对象应该被回收。 漏标是指本来是live object但是由于没有遍历到被当成garbage回收掉了 产生漏标 ①. 标记进行时增加了一个黑到白的引用如果不重新对黑色进行处理则会漏标 ②. 标记进行时删除了灰对象到白对象的引用那么这个白对象有可能被漏标 打破上述两个条件之一即可解决漏标问题 ①. incremental update -- 增量更新关注引用的增加把黑色重新标记为灰色下次重新扫描属性CMS使用。 ②. SATB snapshot at the beginning – 关注引用的删除当B-D消失时要把这个引用推到GC的堆栈保证D还能被GC扫描到G1使用。 3.最终标记 STW 重新标记 4.筛选回收 STW 并行 10、为什么G1用SATB 灰色 → 白色 引用消失时如果没有黑色指向白色引用会被push到堆栈。 下次扫描时拿到这个引用由于有RSet的存在不需要扫描整个堆去查找指向白色的引用效率比较高。SATB 配合 RSet 浑然天成 11、G1的Full GC java 10以前是串行FullGC之后是并行FullGC 12、G1新老年代比例 5%-60%一般不用手工指定也不要手工指定因为这是G1预测停顿时间的基准 13、每个Region有多大 取值1 2 4 8 16 32 即2的幂次方 手工指定 -XX:G1HeapRegionSize 3、G1特点
并发收集压缩空闲空间不会延长GC的暂停时间更易预测的GC暂停时间适用不需要实现很高的吞吐量的场景 4、CMS日志分析
JVM Optimization Learning(四)
中的JVM Optimization Case环境继续使用此环境
[rootlocalhost java]# java -Xms20M -Xmx20M -XX:PrintGCDetails -XX:UseConcMarkSweepGC com.lwz.jvm.T15_FullGC_Problem01
[GC (Allocation Failure) [ParNew: 5504K-640K(6144K), 0.0124495 secs] 5504K-1049K(19840K), 0.0126009 secs] [Times: user0.01 sys0.01, real0.02 secs]
[GC (Allocation Failure) [ParNew: 6144K-640K(6144K), 0.0273421 secs] 6553K-2858K(19840K), 0.0274255 secs] [Times: user0.08 sys0.00, real0.02 secs]
[GC (Allocation Failure) [ParNew: 6144K-640K(6144K), 0.0169154 secs] 8362K-6127K(19840K), 0.0171555 secs] [Times: user0.05 sys0.00, real0.02 secs]
[GC (Allocation Failure) [ParNew: 6144K-640K(6144K), 0.0139854 secs] 11631K-9628K(19840K), 0.0140778 secs] [Times: user0.05 sys0.00, real0.02 secs]
[GC (CMS Initial Mark) [1 CMS-initial-mark: 8988K(13696K)] 9628K(19840K), 0.0014297 secs] [Times: user0.00 sys0.00, real0.00 secs]
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.030/0.030 secs] [Times: user0.04 sys0.00, real0.03 secs]
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.001/0.001 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Final Remark) [YG occupancy: 1274 K (6144 K)][Rescan (parallel) , 0.0012268 secs][weak refs processing, 0.0000665 secs][class unloading, 0.0014624 secs][scrub symbol table, 0.0007199 secs][scrub string table, 0.0003808 secs][1 CMS-remark: 8988K(13696K)] 10262K(19840K), 0.0041094 secs] [Times: user0.00 sys0.00, real0.00 secs]
[CMS-concurrent-sweep-start]
[CMS-concurrent-sweep: 0.015/0.015 secs] [Times: user0.01 sys0.00, real0.01 secs]
[CMS-concurrent-reset-start]
[CMS-concurrent-reset: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Initial Mark) [1 CMS-initial-mark: 8926K(13696K)] 10982K(19840K), 0.0012949 secs] [Times: user0.01 sys0.00, real0.00 secs]
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.018/0.018 secs] [Times: user0.02 sys0.00, real0.02 secs]
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.002/0.002 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Final Remark) [YG occupancy: 2056 K (6144 K)][Rescan (parallel) , 0.0006445 secs][weak refs processing, 0.0000152 secs][class unloading, 0.0008104 secs][scrub symbol table, 0.0005612 secs][scrub string table, 0.0002756 secs][1 CMS-remark: 8926K(13696K)] 10982K(19840K), 0.0024193 secs] [Times: user0.00 sys0.00, real0.01 secs]
[CMS-concurrent-sweep-start]
[CMS-concurrent-sweep: 0.005/0.005 secs] [Times: user0.01 sys0.00, real0.00 secs]
[CMS-concurrent-reset-start]
[CMS-concurrent-reset: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Initial Mark) [1 CMS-initial-mark: 8926K(13696K)] 11454K(19840K), 0.0018331 secs] [Times: user0.00 sys0.00, real0.00 secs]
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.031/0.031 secs] [Times: user0.04 sys0.00, real0.03 secs]
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.004/0.004 secs] [Times: user0.00 sys0.00, real0.01 secs]
[GC (CMS Final Remark) [YG occupancy: 2528 K (6144 K)][Rescan (parallel) , 0.0086513 secs][weak refs processing, 0.0000225 secs][class unloading, 0.0009794 secs][scrub symbol table, 0.0005974 secs][scrub string table, 0.0002462 secs][1 CMS-remark: 8926K(13696K)] 11454K(19840K), 0.0106071 secs] [Times: user0.04 sys0.00, real0.01 secs]
[CMS-concurrent-sweep-start]
[CMS-concurrent-sweep: 0.005/0.005 secs] [Times: user0.00 sys0.00, real0.01 secs]
[CMS-concurrent-reset-start]
[CMS-concurrent-reset: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Initial Mark) [1 CMS-initial-mark: 8926K(13696K)] 11791K(19840K), 0.0017124 secs] [Times: user0.01 sys0.00, real0.01 secs]
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.028/0.028 secs] [Times: user0.03 sys0.00, real0.02 secs]
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.002/0.002 secs] [Times: user0.00 sys0.00, real0.01 secs]
[CMS-concurrent-abortable-preclean-start]CMS: abort preclean due to time [CMS-concurrent-abortable-preclean: 1.068/5.088 secs] [Times: user1.51 sys0.00, real5.08 secs]
[GC (CMS Final Remark) [YG occupancy: 4373 K (6144 K)][Rescan (parallel) , 0.0016615 secs][weak refs processing, 0.0000167 secs][class unloading, 0.0007608 secs][scrub symbol table, 0.0005483 secs][scrub string table, 0.0002508 secs][1 CMS-remark: 8926K(13696K)] 13299K(19840K), 0.0033322 secs] [Times: user0.00 sys0.00, real0.01 secs]
[CMS-concurrent-sweep-start]
[CMS-concurrent-sweep: 0.007/0.007 secs] [Times: user0.01 sys0.00, real0.00 secs]
[CMS-concurrent-reset-start]
[CMS-concurrent-reset: 0.012/0.012 secs] [Times: user0.01 sys0.00, real0.02 secs]
[GC (CMS Initial Mark) [1 CMS-initial-mark: 8926K(13696K)] 13771K(19840K), 0.0030760 secs] [Times: user0.01 sys0.00, real0.00 secs]
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.027/0.027 secs] [Times: user0.03 sys0.00, real0.03 secs]
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.005/0.005 secs] [Times: user0.00 sys0.00, real0.00 secs]
[CMS-concurrent-abortable-preclean-start]
[CMS-concurrent-abortable-preclean: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Final Remark) [YG occupancy: 4845 K (6144 K)][Rescan (parallel) , 0.0024014 secs][weak refs processing, 0.0000203 secs][class unloading, 0.0010572 secs][scrub symbol table, 0.0007175 secs][scrub string table, 0.0003684 secs][1 CMS-remark: 8926K(13696K)] 13771K(19840K), 0.0046857 secs] [Times: user0.02 sys0.00, real0.01 secs]
[CMS-concurrent-sweep-start]
[CMS-concurrent-sweep: 0.007/0.007 secs] [Times: user0.00 sys0.00, real0.01 secs]
[CMS-concurrent-reset-start]
[CMS-concurrent-reset: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Initial Mark) [1 CMS-initial-mark: 8926K(13696K)] 14998K(19840K), 0.0048182 secs] [Times: user0.01 sys0.00, real0.00 secs]
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.021/0.021 secs] [Times: user0.03 sys0.00, real0.02 secs]
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.004/0.004 secs] [Times: user0.00 sys0.00, real0.01 secs]
[CMS-concurrent-abortable-preclean-start]
[CMS-concurrent-abortable-preclean: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (CMS Final Remark) [YG occupancy: 6072 K (6144 K)][Rescan (parallel) , 0.0032505 secs][weak refs processing, 0.0000216 secs][class unloading, 0.0010294 secs][scrub symbol table, 0.0006718 secs][scrub string table, 0.0003728 secs][1 CMS-remark: 8926K(13696K)] 14998K(19840K), 0.0055128 secs] [Times: user0.02 sys0.00, real0.00 secs]
[CMS-concurrent-sweep-start]
[CMS-concurrent-sweep: 0.011/0.011 secs] [Times: user0.01 sys0.00, real0.01 secs]
[CMS-concurrent-reset-start]
[CMS-concurrent-reset: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]
[GC (Allocation Failure) [ParNew: 6144K-640K(6144K), 0.0149299 secs] 14864K-12924K(19840K), 0.0150074 secs] [Times: user0.06 sys0.00, real0.02 secs]
[GC (CMS Initial Mark) [1 CMS-initial-mark: 12284K(13696K)] 13014K(19840K), 0.0008257 secs] [Times: user0.00 sys0.00, real0.00 secs]
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.026/0.026 secs] [Times: user0.03 sys0.00, real0.02 secs]
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.001/0.001 secs] [Times: user0.00 sys0.00, real0.01 secs]
[GC (CMS Final Remark) [YG occupancy: 1336 K (6144 K)][Rescan (parallel) , 0.0007401 secs][weak refs processing, 0.0000219 secs][class unloading, 0.0010162 secs][scrub symbol table, 0.0006404 secs][scrub string table, 0.0004188 secs][1 CMS-remark: 12284K(13696K)] 13621K(19840K), 0.0029844 secs] [Times: user0.00 sys0.00, real0.00 secs]
[CMS-concurrent-sweep-start]ParNew年轻代
[GC (Allocation Failure) [ParNew: 5504K-640K(6144K), 0.0124495 secs] 5504K-1049K(19840K), 0.0126009 secs] [Times: user0.01 sys0.01, real0.02 secs]
ParNew年轻代收集器
5504K-640K收集前后的对比
(6144K)整个年轻代容量
5504K-1049K整个堆的情况
(19840K)整个堆大小
CMS老年代回收日志---主要看1.频繁不频繁2.花的时间长不长是不是在我允许的范围之内
[GC (CMS Initial Mark) [1 CMS-initial-mark: 8988K(13696K)] 9628K(19840K), 0.0014297 secs][Times: user0.00 sys0.00, real0.00 secs]//8988K(13696K) : 老年代使用最大//9628K(19840K) : 整个堆使用最大
[CMS-concurrent-mark-start]
[CMS-concurrent-mark: 0.030/0.030 secs] [Times: user0.04 sys0.00, real0.03 secs]//这里的时间意义不大因为是并发执行
[CMS-concurrent-preclean-start]
[CMS-concurrent-preclean: 0.001/0.001 secs] [Times: user0.00 sys0.00, real0.00 secs]//标记Card为Dirty也称为Card Marking
[GC (CMS Final Remark) [YG occupancy: 1274 K (6144 K)][Rescan (parallel) , 0.0012268 secs]
[weak refs processing, 0.0000665 secs][class unloading, 0.0014624 secs][scrub symbol table,0.0007199 secs][scrub string table, 0.0003808 secs][1 CMS-remark: 8988K(13696K)]10262K(19840K), 0.0041094 secs] [Times: user0.00 sys0.00, real0.00 secs]//STW阶段YG occupancy:年轻代占用及容量//[Rescan (parallel)STW下的存活对象标记//weak refs processing: 弱引用处理//class unloading: 卸载用不到的class//scrub symbol(string) table: //cleaning up symbol and string tables which hold class-level metadata and //internalized string respectively//CMS-remark: 8988K(13696K): 阶段过后的老年代占用及容量//10262K(19840K): 阶段过后的堆占用及容量
[CMS-concurrent-sweep-start]
[CMS-concurrent-sweep: 0.015/0.015 secs] [Times: user0.01 sys0.00, real0.01 secs]//标记已经完成进行并发清理
[CMS-concurrent-reset-start]
[CMS-concurrent-reset: 0.000/0.000 secs] [Times: user0.00 sys0.00, real0.00 secs]//重置内部结构为下次GC做准备 5、G1日志分析
JVM Optimization Learning(四) ---JVM Optimization Case环境继续使用此环境
[rootlocalhost java]# java -Xms20M -Xmx20M -XX:PrintGCDetails -XX:UseG1GC com.lwz.jvm.T15_FullGC_Problem01
[GC pause (G1 Evacuation Pause) (young), 0.0091218 secs][Parallel Time: 7.8 ms, GC Workers: 4][GC Worker Start (ms): Min: 7838.5, Avg: 7842.2, Max: 7846.0, Diff: 7.5][Ext Root Scanning (ms): Min: 0.0, Avg: 1.0, Max: 2.0, Diff: 2.0, Sum: 4.0][Update RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Processed Buffers: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Code Root Scanning (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 0.2][Object Copy (ms): Min: 0.0, Avg: 2.5, Max: 5.2, Diff: 5.2, Sum: 10.0][Termination (ms): Min: 0.0, Avg: 0.2, Max: 0.4, Diff: 0.4, Sum: 1.0][Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.1][GC Worker Total (ms): Min: 0.1, Avg: 3.9, Max: 7.6, Diff: 7.6, Sum: 15.5][GC Worker End (ms): Min: 7846.1, Avg: 7846.1, Max: 7846.1, Diff: 0.1][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.3 ms][Other: 1.0 ms][Choose CSet: 0.0 ms][Ref Proc: 0.5 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.3 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 12.0M(12.0M)-0.0B(10.0M) Survivors: 0.0B-2048.0K Heap: 12.0M(20.0M)-1952.0K(20.0M)][Times: user0.02 sys0.01, real0.01 secs]
[GC pause (G1 Evacuation Pause) (young), 0.0184956 secs][Parallel Time: 16.2 ms, GC Workers: 4][GC Worker Start (ms): Min: 31098.3, Avg: 31098.9, Max: 31099.7, Diff: 1.3][Ext Root Scanning (ms): Min: 0.4, Avg: 2.9, Max: 8.0, Diff: 7.6, Sum: 11.4][Update RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Processed Buffers: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Code Root Scanning (ms): Min: 0.0, Avg: 0.1, Max: 0.4, Diff: 0.4, Sum: 0.4][Object Copy (ms): Min: 7.5, Avg: 12.4, Max: 14.2, Diff: 6.7, Sum: 49.7][Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Termination Attempts: Min: 3, Avg: 4.2, Max: 8, Diff: 5, Sum: 17][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.1][GC Worker Total (ms): Min: 14.6, Avg: 15.4, Max: 15.9, Diff: 1.3, Sum: 61.7][GC Worker End (ms): Min: 31114.3, Avg: 31114.3, Max: 31114.3, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.8 ms][Other: 1.4 ms][Choose CSet: 0.0 ms][Ref Proc: 0.6 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.6 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 10.0M(10.0M)-0.0B(7168.0K) Survivors: 2048.0K-2048.0K Heap: 11.9M(20.0M)-6817.5K(20.0M)][Times: user0.05 sys0.01, real0.02 secs]
[GC pause (G1 Evacuation Pause) (young) (to-space exhausted), 0.0245234 secs][Parallel Time: 16.8 ms, GC Workers: 4][GC Worker Start (ms): Min: 53252.5, Avg: 53252.7, Max: 53252.9, Diff: 0.4][Ext Root Scanning (ms): Min: 0.5, Avg: 0.7, Max: 0.9, Diff: 0.4, Sum: 2.8][Update RS (ms): Min: 2.9, Avg: 3.0, Max: 3.3, Diff: 0.4, Sum: 12.0][Processed Buffers: Min: 12, Avg: 14.2, Max: 18, Diff: 6, Sum: 57][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.2][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 12.1, Avg: 12.3, Max: 12.5, Diff: 0.5, Sum: 49.3][Termination (ms): Min: 0.0, Avg: 0.2, Max: 0.3, Diff: 0.3, Sum: 0.6][Termination Attempts: Min: 1, Avg: 1.2, Max: 2, Diff: 1, Sum: 5][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1][GC Worker Total (ms): Min: 16.1, Avg: 16.2, Max: 16.5, Diff: 0.4, Sum: 65.0][GC Worker End (ms): Min: 53269.0, Avg: 53269.0, Max: 53269.0, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.7 ms][Other: 7.0 ms][Evacuation Failure: 5.8 ms][Choose CSet: 0.0 ms][Ref Proc: 0.4 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.6 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 7168.0K(7168.0K)-0.0B(1024.0K) Survivors: 2048.0K-2048.0K Heap: 13.7M(20.0M)-19.0M(20.0M)][Times: user0.08 sys0.00, real0.02 secs]
[GC pause (G1 Evacuation Pause) (young) (initial-mark) (to-space exhausted), 0.0435448 secs][Parallel Time: 35.5 ms, GC Workers: 4][GC Worker Start (ms): Min: 56073.6, Avg: 56073.8, Max: 56073.9, Diff: 0.3][Ext Root Scanning (ms): Min: 0.5, Avg: 0.6, Max: 0.8, Diff: 0.3, Sum: 2.5][Update RS (ms): Min: 0.0, Avg: 3.5, Max: 14.1, Diff: 14.1, Sum: 14.1][Processed Buffers: Min: 0, Avg: 14.2, Max: 57, Diff: 57, Sum: 57][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.1][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 20.1, Avg: 30.9, Max: 34.6, Diff: 14.5, Sum: 123.6][Termination (ms): Min: 0.0, Avg: 0.2, Max: 0.4, Diff: 0.4, Sum: 0.7][Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][GC Worker Total (ms): Min: 35.1, Avg: 35.2, Max: 35.4, Diff: 0.3, Sum: 141.0][GC Worker End (ms): Min: 56109.0, Avg: 56109.0, Max: 56109.0, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.6 ms][Other: 7.4 ms][Evacuation Failure: 6.4 ms][Choose CSet: 0.0 ms][Ref Proc: 0.4 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.5 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 1024.0K(1024.0K)-0.0B(1024.0K) Survivors: 2048.0K-0.0B Heap: 20.0M(20.0M)-20.0M(20.0M)][Times: user0.07 sys0.00, real0.04 secs]
[GC concurrent-root-region-scan-start]
[GC concurrent-root-region-scan-end, 0.0001056 secs]
[GC concurrent-mark-start]
[Full GC (Allocation Failure) 20M-11M(20M), 0.0384932 secs][Eden: 0.0B(1024.0K)-0.0B(3072.0K) Survivors: 0.0B-0.0B Heap: 20.0M(20.0M)-11.1M(20.0M)], [Metaspace: 3879K-3873K(1056768K)][Times: user0.05 sys0.00, real0.04 secs]
[GC concurrent-mark-abort]
[GC pause (G1 Evacuation Pause) (young), 0.0100011 secs][Parallel Time: 8.4 ms, GC Workers: 4][GC Worker Start (ms): Min: 65691.5, Avg: 65691.7, Max: 65691.8, Diff: 0.3][Ext Root Scanning (ms): Min: 0.4, Avg: 0.6, Max: 0.7, Diff: 0.3, Sum: 2.2][Update RS (ms): Min: 3.9, Avg: 4.0, Max: 4.1, Diff: 0.2, Sum: 16.0][Processed Buffers: Min: 13, Avg: 14.8, Max: 17, Diff: 4, Sum: 59][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 3.4, Avg: 3.5, Max: 3.6, Diff: 0.2, Sum: 13.9][Termination (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 0.5][Termination Attempts: Min: 18, Avg: 22.8, Max: 26, Diff: 8, Sum: 91][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1][GC Worker Total (ms): Min: 8.0, Avg: 8.2, Max: 8.4, Diff: 0.3, Sum: 32.8][GC Worker End (ms): Min: 65699.8, Avg: 65699.8, Max: 65699.8, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.5 ms][Other: 1.0 ms][Choose CSet: 0.0 ms][Ref Proc: 0.5 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.4 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 3072.0K(3072.0K)-0.0B(1024.0K) Survivors: 0.0B-1024.0K Heap: 14.1M(20.0M)-13.6M(20.0M)][Times: user0.04 sys0.00, real0.01 secs]
[GC pause (G1 Evacuation Pause) (young) (initial-mark), 0.0105135 secs][Parallel Time: 8.5 ms, GC Workers: 4][GC Worker Start (ms): Min: 69872.2, Avg: 69872.4, Max: 69872.6, Diff: 0.4][Ext Root Scanning (ms): Min: 0.5, Avg: 0.7, Max: 0.9, Diff: 0.4, Sum: 2.7][Update RS (ms): Min: 4.1, Avg: 4.2, Max: 4.3, Diff: 0.2, Sum: 16.7][Processed Buffers: Min: 12, Avg: 14.8, Max: 17, Diff: 5, Sum: 59][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 3.1, Avg: 3.2, Max: 3.3, Diff: 0.2, Sum: 12.8][Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.2][Termination Attempts: Min: 11, Avg: 14.2, Max: 16, Diff: 5, Sum: 57][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1][GC Worker Total (ms): Min: 7.9, Avg: 8.1, Max: 8.3, Diff: 0.4, Sum: 32.6][GC Worker End (ms): Min: 69880.6, Avg: 69880.6, Max: 69880.6, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.7 ms][Other: 1.4 ms][Choose CSet: 0.0 ms][Ref Proc: 0.7 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.5 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 1024.0K(1024.0K)-0.0B(1024.0K) Survivors: 1024.0K-1024.0K Heap: 14.6M(20.0M)-15.4M(20.0M)][Times: user0.03 sys0.00, real0.01 secs]
[GC concurrent-root-region-scan-start]
[GC concurrent-root-region-scan-end, 0.0029410 secs]
[GC concurrent-mark-start]
[GC concurrent-mark-end, 0.0485784 secs]
[GC remark [Finalize Marking, 0.0005557 secs] [GC ref-proc, 0.0003018 secs] [Unloading, 0.0014276 secs], 0.0029364 secs][Times: user0.01 sys0.00, real0.00 secs]
[GC cleanup 15M-15M(20M), 0.0013613 secs][Times: user0.00 sys0.00, real0.00 secs]
[GC pause (G1 Evacuation Pause) (young), 0.0114531 secs][Parallel Time: 9.6 ms, GC Workers: 4][GC Worker Start (ms): Min: 73775.8, Avg: 73775.9, Max: 73776.1, Diff: 0.3][Ext Root Scanning (ms): Min: 0.4, Avg: 0.5, Max: 0.7, Diff: 0.3, Sum: 2.2][Update RS (ms): Min: 5.7, Avg: 5.8, Max: 5.9, Diff: 0.3, Sum: 23.0][Processed Buffers: Min: 15, Avg: 15.2, Max: 16, Diff: 1, Sum: 61][Scan RS (ms): Min: 0.0, Avg: 0.2, Max: 0.3, Diff: 0.2, Sum: 0.7][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 2.7, Avg: 2.8, Max: 2.8, Diff: 0.1, Sum: 11.1][Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1][GC Worker Total (ms): Min: 9.1, Avg: 9.3, Max: 9.4, Diff: 0.3, Sum: 37.0][GC Worker End (ms): Min: 73785.2, Avg: 73785.2, Max: 73785.2, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.6 ms][Other: 1.3 ms][Choose CSet: 0.0 ms][Ref Proc: 0.6 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.4 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 1024.0K(1024.0K)-0.0B(1024.0K) Survivors: 1024.0K-1024.0K Heap: 16.4M(20.0M)-16.7M(20.0M)][Times: user0.04 sys0.00, real0.01 secs]
[GC pause (G1 Evacuation Pause) (mixed) (to-space exhausted), 0.0406284 secs][Parallel Time: 34.3 ms, GC Workers: 4][GC Worker Start (ms): Min: 77404.1, Avg: 77404.4, Max: 77404.7, Diff: 0.6][Ext Root Scanning (ms): Min: 0.3, Avg: 0.6, Max: 0.9, Diff: 0.6, Sum: 2.2][Update RS (ms): Min: 4.1, Avg: 4.2, Max: 4.2, Diff: 0.1, Sum: 16.8][Processed Buffers: Min: 13, Avg: 15.2, Max: 18, Diff: 5, Sum: 61][Scan RS (ms): Min: 0.0, Avg: 0.1, Max: 0.4, Diff: 0.4, Sum: 0.5][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 28.7, Avg: 29.0, Max: 29.1, Diff: 0.4, Sum: 115.9][Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Termination Attempts: Min: 1, Avg: 1.2, Max: 2, Diff: 1, Sum: 5][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1][GC Worker Total (ms): Min: 33.6, Avg: 33.9, Max: 34.2, Diff: 0.6, Sum: 135.4][GC Worker End (ms): Min: 77438.3, Avg: 77438.3, Max: 77438.3, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.5 ms][Other: 5.8 ms][Evacuation Failure: 4.3 ms][Choose CSet: 0.0 ms][Ref Proc: 0.7 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.7 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 1024.0K(1024.0K)-0.0B(1024.0K) Survivors: 1024.0K-1024.0K Heap: 17.7M(20.0M)-19.1M(20.0M)][Times: user0.07 sys0.00, real0.04 secs]
[GC pause (G1 Evacuation Pause) (young) (to-space exhausted), 0.0146382 secs][Parallel Time: 11.7 ms, GC Workers: 4][GC Worker Start (ms): Min: 77445.6, Avg: 77445.8, Max: 77446.3, Diff: 0.7][Ext Root Scanning (ms): Min: 0.0, Avg: 0.4, Max: 0.6, Diff: 0.6, Sum: 1.6][Update RS (ms): Min: 0.0, Avg: 2.3, Max: 5.0, Diff: 5.0, Sum: 9.3][Processed Buffers: Min: 0, Avg: 65.5, Max: 156, Diff: 156, Sum: 262][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 5.6, Avg: 8.3, Max: 10.6, Diff: 5.0, Sum: 33.1][Termination (ms): Min: 0.0, Avg: 0.1, Max: 0.3, Diff: 0.3, Sum: 0.5][Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][GC Worker Total (ms): Min: 10.7, Avg: 11.2, Max: 11.4, Diff: 0.7, Sum: 44.6][GC Worker End (ms): Min: 77457.0, Avg: 77457.0, Max: 77457.0, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.4 ms][Other: 2.6 ms][Evacuation Failure: 1.5 ms][Choose CSet: 0.0 ms][Ref Proc: 0.6 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.4 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 0.0B(1024.0K)-0.0B(1024.0K) Survivors: 1024.0K-0.0B Heap: 19.1M(20.0M)-19.1M(20.0M)][Times: user0.02 sys0.00, real0.01 secs]
G1日志young 参照CMS日志查看
[GC pause (G1 Evacuation Pause) (young), 0.0091218 secs][Parallel Time: 7.8 ms, GC Workers: 4][GC Worker Start (ms): Min: 7838.5, Avg: 7842.2, Max: 7846.0, Diff: 7.5][Ext Root Scanning (ms): Min: 0.0, Avg: 1.0, Max: 2.0, Diff: 2.0, Sum: 4.0][Update RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Processed Buffers: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Code Root Scanning (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 0.2][Object Copy (ms): Min: 0.0, Avg: 2.5, Max: 5.2, Diff: 5.2, Sum: 10.0][Termination (ms): Min: 0.0, Avg: 0.2, Max: 0.4, Diff: 0.4, Sum: 1.0][Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.1][GC Worker Total (ms): Min: 0.1, Avg: 3.9, Max: 7.6, Diff: 7.6, Sum: 15.5][GC Worker End (ms): Min: 7846.1, Avg: 7846.1, Max: 7846.1, Diff: 0.1][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.3 ms] //清理Card table[Other: 1.0 ms][Choose CSet: 0.0 ms][Ref Proc: 0.5 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.3 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 12.0M(12.0M)-0.0B(10.0M) Survivors: 0.0B-2048.0K Heap: 12.0M(20.0M)-1952.0K(20.0M)][Times: user0.02 sys0.01, real0.01 secs]
G1日志mixedGC--混合回收
查看日志回收是否回收正常没回收代表不正常。
[GC pause (G1 Evacuation Pause) (young) (initial-mark) (to-space exhausted), 0.0435448 secs]
//young - 年轻代 Evacuation(疏散撤离)- 复制存活对象
//initial-mark 混合回收的阶段(mixedGC)这里是YGC混合老年代回收[Parallel Time: 35.5 ms, GC Workers: 4] //4个GC线程[GC Worker Start (ms): Min: 56073.6, Avg: 56073.8, Max: 56073.9, Diff: 0.3][Ext Root Scanning (ms): Min: 0.5, Avg: 0.6, Max: 0.8, Diff: 0.3, Sum: 2.5][Update RS (ms): Min: 0.0, Avg: 3.5, Max: 14.1, Diff: 14.1, Sum: 14.1][Processed Buffers: Min: 0, Avg: 14.2, Max: 57, Diff: 57, Sum: 57][Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.1][Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][Object Copy (ms): Min: 20.1, Avg: 30.9, Max: 34.6, Diff: 14.5, Sum: 123.6][Termination (ms): Min: 0.0, Avg: 0.2, Max: 0.4, Diff: 0.4, Sum: 0.7][Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4][GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0][GC Worker Total (ms): Min: 35.1, Avg: 35.2, Max: 35.4, Diff: 0.3, Sum: 141.0][GC Worker End (ms): Min: 56109.0, Avg: 56109.0, Max: 56109.0, Diff: 0.0][Code Root Fixup: 0.0 ms][Code Root Purge: 0.0 ms][Clear CT: 0.6 ms] //清理Card table[Other: 7.4 ms][Evacuation Failure: 6.4 ms][Choose CSet: 0.0 ms][Ref Proc: 0.4 ms][Ref Enq: 0.0 ms][Redirty Cards: 0.5 ms][Humongous Register: 0.0 ms][Humongous Reclaim: 0.0 ms][Free CSet: 0.0 ms][Eden: 1024.0K(1024.0K)-0.0B(1024.0K) Survivors: 2048.0K-0.0B
Heap: 20.0M(20.0M)-20.0M(20.0M)][Times: user0.07 sys0.00, real0.04 secs]
//以下是混合回收其他阶段
[GC concurrent-root-region-scan-start]
[GC concurrent-root-region-scan-end, 0.0001056 secs]
[GC concurrent-mark-start]
//无法evacuation进行FGC
[Full GC (Allocation Failure) 20M-11M(20M), 0.0384932 secs][Eden: 0.0B(1024.0K)-0.0B(3072.0K) Survivors: 0.0B-0.0B
Heap: 20.0M(20.0M)-11.1M(20.0M)], [Metaspace: 3879K-3873K(1056768K)][Times: user0.05 sys0.00, real0.04 secs]
[GC concurrent-mark-abort] 2、GC参数
2.1、GC常用参数 -Xmn -Xms -Xmx -Xss 年轻代 最小堆 最大堆 栈空间 -XX:UseTLAB 使用TLAB默认打开 -XX:PrintTLAB 打印TLAB的使用情况 -XX:TLABSize 设置TLAB大小 -XX:DisableExplictGC System.gc()不管用 FGC -XX:PrintGC 打印GC信息 -XX:PrintGCDetails 打印GC详细信息 -XX:PrintHeapAtGC 打印GC堆栈信息 -XX:PrintGCTimeStamps 打印发生GC系统信息 -XX:PrintGCApplicationConcurrentTime (低) 打印应用程序时间 -XX:PrintGCApplicationStoppedTime 低 打印应用程序暂停时长 -XX:PrintReferenceGC 重要性低 记录回收了多少种不同引用类型的引用 -verbose:class 类加载详细过程 -XX:PrintVMOptions 打印JVM运行时参数 -XX:PrintFlagsFinal (需要会) 查找JVM命令设置的最终值 [rootlocalhost ~]# java -XX:PrintFlagsFinal -version | grep G1double G1ConcMarkStepDurationMillis 10.000000 {product}uintx G1ConcRSHotCardLimit 4 {product}uintx G1ConcRSLogCacheSize 10 {product}intx G1ConcRefinementGreenZone 0 {product}intx G1ConcRefinementRedZone 0 {product}intx G1ConcRefinementServiceIntervalMillis 300 {product}uintx G1ConcRefinementThreads 0 {product}intx G1ConcRefinementThresholdStep 0 {product}intx G1ConcRefinementYellowZone 0 {product}uintx G1ConfidencePercent 50 {product}uintx G1HeapRegionSize 0 {product}uintx G1HeapWastePercent 5 {product}uintx G1MixedGCCountTarget 8 {product}intx G1RSetRegionEntries 0 {product}uintx G1RSetScanBlockSize 64 {product}intx G1RSetSparseRegionEntries 0 {product}intx G1RSetUpdatingPauseTimePercent 10 {product}intx G1RefProcDrainInterval 10 {product}uintx G1ReservePercent 10 {product}uintx G1SATBBufferEnqueueingThresholdPercent 60 {product}intx G1SATBBufferSize 1024 {product}intx G1UpdateBufferSize 256 {product}bool G1UseAdaptiveConcRefinement true {product}bool UseG1GC false {product}
java version 1.8.0_202
Java(TM) SE Runtime Environment (build 1.8.0_202-b08)
Java HotSpot(TM) 64-Bit Server VM (build 25.202-b08, mixed mode)-XX:PrintFlagsInitial (需要会) 查找JVM命令初始化默认值 [rootlocalhost ~]# java -XX:PrintFlagsInitial -version | grep CMSbool CMSAbortSemantics false {product}uintx CMSAbortablePrecleanMinWorkPerIteration 100 {product}intx CMSAbortablePrecleanWaitMillis 100 {manageable}uintx CMSBitMapYieldQuantum 10485760 {product}uintx CMSBootstrapOccupancy 50 {product}bool CMSClassUnloadingEnabled true {product}uintx CMSClassUnloadingMaxInterval 0 {product}bool CMSCleanOnEnter true {product}bool CMSCompactWhenClearAllSoftRefs true {product}uintx CMSConcMarkMultiple 32 {product}bool CMSConcurrentMTEnabled true {product}uintx CMSCoordinatorYieldSleepCount 10 {product}bool CMSDumpAtPromotionFailure false {product}bool CMSEdenChunksRecordAlways true {product}uintx CMSExpAvgFactor 50 {product}bool CMSExtrapolateSweep false {product}uintx CMSFullGCsBeforeCompaction 0 {product}uintx CMSIncrementalDutyCycle 10 {product}uintx CMSIncrementalDutyCycleMin 0 {product}bool CMSIncrementalMode false {product}uintx CMSIncrementalOffset 0 {product}bool CMSIncrementalPacing true {product}uintx CMSIncrementalSafetyFactor 10 {product}uintx CMSIndexedFreeListReplenish 4 {product}intx CMSInitiatingOccupancyFraction -1 {product}uintx CMSIsTooFullPercentage 98 {product}double CMSLargeCoalSurplusPercent 0.950000 {product}double CMSLargeSplitSurplusPercent 1.000000 {product}bool CMSLoopWarn false {product}uintx CMSMaxAbortablePrecleanLoops 0 {product}intx CMSMaxAbortablePrecleanTime 5000 {product}uintx CMSOldPLABMax 1024 {product}uintx CMSOldPLABMin 16 {product}uintx CMSOldPLABNumRefills 4 {product}uintx CMSOldPLABReactivityFactor 2 {product}bool CMSOldPLABResizeQuicker false {product}uintx CMSOldPLABToleranceFactor 4 {product}bool CMSPLABRecordAlways true {product}uintx CMSParPromoteBlocksToClaim 16 {product}bool CMSParallelInitialMarkEnabled true {product}bool CMSParallelRemarkEnabled true {product}bool CMSParallelSurvivorRemarkEnabled true {product}uintx CMSPrecleanDenominator 3 {product}uintx CMSPrecleanIter 3 {product}uintx CMSPrecleanNumerator 2 {product}bool CMSPrecleanRefLists1 true {product}bool CMSPrecleanRefLists2 false {product}bool CMSPrecleanSurvivors1 false {product}bool CMSPrecleanSurvivors2 true {product}uintx CMSPrecleanThreshold 1000 {product}bool CMSPrecleaningEnabled true {product}bool CMSPrintChunksInDump false {product}bool CMSPrintEdenSurvivorChunks false {product}bool CMSPrintObjectsInDump false {product}uintx CMSRemarkVerifyVariant 1 {product}bool CMSReplenishIntermediate true {product}uintx CMSRescanMultiple 32 {product}uintx CMSSamplingGrain 16384 {product}bool CMSScavengeBeforeRemark false {product}uintx CMSScheduleRemarkEdenPenetration 50 {product}uintx CMSScheduleRemarkEdenSizeThreshold 2097152 {product}uintx CMSScheduleRemarkSamplingRatio 5 {product}double CMSSmallCoalSurplusPercent 1.050000 {product}double CMSSmallSplitSurplusPercent 1.100000 {product}bool CMSSplitIndexedFreeListBlocks true {product}intx CMSTriggerInterval -1 {manageable}uintx CMSTriggerRatio 80 {product}intx CMSWaitDuration 2000 {manageable}uintx CMSWorkQueueDrainThreshold 10 {product}bool CMSYield true {product}uintx CMSYieldSleepCount 0 {product}uintx CMSYoungGenPerWorker 67108864 {pd product}uintx CMS_FLSPadding 1 {product}uintx CMS_FLSWeight 75 {product}uintx CMS_SweepPadding 1 {product}uintx CMS_SweepTimerThresholdMillis 10 {product}uintx CMS_SweepWeight 75 {product}bool PrintCMSInitiationStatistics false {product}intx PrintCMSStatistics 0 {product}bool UseCMSBestFit true {product}bool UseCMSCollectionPassing true {product}bool UseCMSCompactAtFullCollection true {product}bool UseCMSInitiatingOccupancyOnly false {product}
[rootlocalhost ~]#-Xloggc:opt/log/gc.log -XX:MaxTenuringThreshold GC升代年龄最大值15 锁自旋次数 -XX:PreBlockSpin 热点代码检测参数-XX:CompileThreshold 逃逸分析 标量替换 不建议设置 2.2、Parallel常用参数 -XX:SurvivorRatio -XX:PreTenureSizeThreshold 大对象到底多大 -XX:MaxTenuringThreshold GC升代年龄最大值15 -XX:ParallelGCThreads 并行收集器的线程数同样适用于CMS一般设为和CPU核数相同 -XX:UseAdaptiveSizePolicy 自动选择各区大小比例 2.3、CMS常用参数 -XX:UseConcMarkSweepGC 启动CMS垃圾回收器 -XX:ParallelCMSThreads CMS线程数量 -XX:CMSInitiatingOccupancyFraction 使用多少比例的老年代后开始CMS收集默认是68%(近似值)如果频繁发生SerialOld卡顿应该调小频繁CMS回收 怎么解决CMS回收器浮动垃圾和碎片化的问题-XX:UseCMSCompactAtFullCollection 在FGC时进行压缩 -XX:CMSFullGCsBeforeCompaction 多少次FGC之后进行压缩 -XX:CMSClassUnloadingEnabled 回收不用的class -XX:CMSInitiatingPermOccupancyFraction 达到什么比例时进行Perm回收 GCTimeRatio 设置GC时间占用程序运行时间的百分比是一个建议时间 -XX:MaxGCPauseMillis 停顿时间是一个建议时间GC会尝试用各种手段达到这个时间比如减小年轻代 2.4、G1常用参数 -XX:UseG1GC 启动G1GC -XX:MaxGCPauseMillis 建议值G1会尝试调整Young区的块数来达到这个值 -XX:GCPauseIntervalMillis GC的间隔时间 -XX:G1HeapRegionSize 设置分区大小建议逐渐增大该值1 2 4 8 16 32。 随着size增加垃圾的存活时间更长GC间隔更长但每次GC的时间也会更长 ZGC做了改进动态区块大小 G1NewSizePercent 新生代最小比例默认为5% G1MaxNewSizePercent 新生代最大比例默认为60% GCTimeRatio GC时间建议比例G1会根据这个值调整堆空间 ConcGCThreads 线程数量 InitiatingHeapOccupancyPercent 启动G1的堆空间占用比例 JVM Optimization Learning(四) 不断学习才能不断提高 生如蝼蚁当立鸿鹄之志命比纸薄应有不屈之心。 乾坤未定你我皆是黑马若乾坤已定谁敢说我不能逆转乾坤 努力吧机会永远是留给那些有准备的人否则机会来了没有实力只能眼睁睁地看着机会溜走。
