JDK11的ZGC小试牛刀
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本文主要试一下JDK11的ZGC
ZGC
ZGC全称是Z Garbage Collector，是一款可伸缩(scalable)的低延迟(low latency garbage)、并发(concurrent)垃圾回收器，旨在实现以下几个目标：
- 停顿时间不超过10ms
- 停顿时间不随heap大小或存活对象大小增大而增大
- 可以处理从几百兆到几T的内存大小
设置
-server -XX:+UnlockExperimentalVMOptions -XX:+UseZGC -Xlog:age*,gc*=info:file=gc-%t.log:time,tid,tags:filecount=3,filesize=20m -Djava.io.tmpdir=/tmp'log实例
[2018-07-22T13:17:59.526+0000][7][gc,init] Initializing The Z Garbage Collector
[2018-07-22T13:17:59.526+0000][7][gc,init] Version: 11-ea+22 (release)
[2018-07-22T13:17:59.526+0000][7][gc,init] NUMA Support: Disabled
[2018-07-22T13:17:59.526+0000][7][gc,init] CPUs: 2 total, 2 available
[2018-07-22T13:17:59.530+0000][7][gc,init] Memory: 2001M
[2018-07-22T13:17:59.530+0000][7][gc,init] Large Page Support: Disabled
[2018-07-22T13:17:59.530+0000][7][gc,init] Workers: 4 parallel, 4 concurrent
[2018-07-22T13:17:59.531+0000][7][gc,init] Heap backed by file: /memfd:java_heap
[2018-07-22T13:17:59.532+0000][7][gc,init] Available space on backing filesystem: N/A
[2018-07-22T13:17:59.540+0000][7][gc,init] Pre-touching: Disabled
[2018-07-22T13:17:59.540+0000][7][gc,init] Pre-mapping: 32M
[2018-07-22T13:17:59.576+0000][7][gc,init] Runtime Workers: 4 parallel
[2018-07-22T13:17:59.584+0000][7][gc ] Using The Z Garbage Collector
[2018-07-22T13:18:01.071+0000][13][gc,start] GC(0) Garbage Collection (Warmup)
[2018-07-22T13:18:01.072+0000][19][gc,phases] GC(0) Pause Mark Start 0.370ms
[2018-07-22T13:18:01.102+0000][13][gc,phases] GC(0) Concurrent Mark 29.459ms
[2018-07-22T13:18:01.102+0000][19][gc,phases] GC(0) Pause Mark End 0.513ms
[2018-07-22T13:18:01.103+0000][13][gc,phases] GC(0) Concurrent Process Non-Strong References 0.410ms
[2018-07-22T13:18:01.103+0000][13][gc,phases] GC(0) Concurrent Reset Relocation Set 0.000ms
[2018-07-22T13:18:01.103+0000][13][gc,phases] GC(0) Concurrent Destroy Detached Pages 0.000ms
[2018-07-22T13:18:01.105+0000][13][gc,phases] GC(0) Concurrent Select Relocation Set 1.739ms
[2018-07-22T13:18:01.105+0000][13][gc,phases] GC(0) Concurrent Prepare Relocation Set 0.342ms
[2018-07-22T13:18:01.112+0000][19][gc,phases] GC(0) Pause Relocate Start 7.167ms
[2018-07-22T13:18:01.126+0000][13][gc,phases] GC(0) Concurrent Relocate 9.600ms
[2018-07-22T13:18:01.126+0000][13][gc,load ] GC(0) Load: 0.09/0.43/0.23
[2018-07-22T13:18:01.128+0000][13][gc,mmu ] GC(0) MMU: 2ms/0.0%, 5ms/0.0%, 10ms/27.3%, 20ms/61.6%, 50ms/83.9%, 100ms/92.0%
[2018-07-22T13:18:01.129+0000][13][gc,marking] GC(0) Mark: 4 stripe(s), 1 proactive flush(es), 2 terminate flush(es), 1 completion(s), 0 continuation(s)
[2018-07-22T13:18:01.129+0000][13][gc,reloc ] GC(0) Relocation: Successful, 3M relocated
[2018-07-22T13:18:01.129+0000][13][gc,nmethod] GC(0) NMethods: 379 registered, 0 unregistered
[2018-07-22T13:18:01.129+0000][13][gc,metaspace] GC(0) Metaspace: 14M used, 14M capacity, 14M committed, 16M reserved
[2018-07-22T13:18:01.129+0000][13][gc,ref ] GC(0) Soft: 491 encountered, 0 discovered, 0 enqueued
[2018-07-22T13:18:01.129+0000][13][gc,ref ] GC(0) Weak: 477 encountered, 334 discovered, 102 enqueued
[2018-07-22T13:18:01.129+0000][13][gc,ref ] GC(0) Final: 57 encountered, 0 discovered, 0 enqueued
[2018-07-22T13:18:01.129+0000][13][gc,ref ] GC(0) Phantom: 1229 encountered, 1227 discovered, 1223 enqueued
[2018-07-22T13:18:01.129+0000][13][gc,heap ] GC(0) Mark Start Mark End Relocate Start Relocate End High Low
[2018-07-22T13:18:01.129+0000][13][gc,heap ] GC(0) Capacity: 92M (18%) 96M (19%) 96M (19%) 102M (20%) 102M (20%) 92M (18%)
[2018-07-22T13:18:01.129+0000][13][gc,heap ] GC(0) Reserve: 40M (8%) 40M (8%) 40M (8%) 40M (8%) 40M (8%) 40M (8%)
[2018-07-22T13:18:01.129+0000][13][gc,heap ] GC(0) Free: 410M (82%) 406M (81%) 406M (81%) 448M (89%) 448M (89%) 400M (80%)
[2018-07-22T13:18:01.129+0000][13][gc,heap ] GC(0) Used: 52M (10%) 56M (11%) 56M (11%) 14M (3%) 62M (12%) 14M (3%)
[2018-07-22T13:18:01.129+0000][13][gc,heap ] GC(0) Live: - 3M (1%) 3M (1%) 3M (1%) - -
[2018-07-22T13:18:01.129+0000][13][gc,heap ] GC(0) Allocated: - 4M (1%) 4M (1%) 12M (2%) - -
[2018-07-22T13:18:01.132+0000][13][gc,heap ] GC(0) Garbage: - 48M (10%) 48M (10%) 4M (1%) - -
[2018-07-22T13:18:01.132+0000][13][gc,heap ] GC(0) Reclaimed: - - 0M (0%) 44M (9%) - -
[2018-07-22T13:18:01.132+0000][13][gc ] GC(0) Garbage Collection (Warmup) 52M(10%)->14M(3%)
[2018-07-22T13:18:02.172+0000][13][gc,start ] GC(1) Garbage Collection (Warmup)
[2018-07-22T13:18:02.173+0000][19][gc,phases ] GC(1) Pause Mark Start 0.776ms
[2018-07-22T13:18:02.198+0000][13][gc,phases ] GC(1) Concurrent Mark 24.883ms
[2018-07-22T13:18:02.198+0000][19][gc,phases ] GC(1) Pause Mark End 0.256ms
[2018-07-22T13:18:02.205+0000][13][gc,phases ] GC(1) Concurrent Process Non-Strong References 6.484ms
[2018-07-22T13:18:02.205+0000][13][gc,phases ] GC(1) Concurrent Reset Relocation Set 0.005ms
[2018-07-22T13:18:02.205+0000][13][gc,phases ] GC(1) Concurrent Destroy Detached Pages 0.000ms
[2018-07-22T13:18:02.206+0000][13][gc,phases ] GC(1) Concurrent Select Relocation Set 1.104ms
[2018-07-22T13:18:02.210+0000][13][gc,phases ] GC(1) Concurrent Prepare Relocation Set 3.879ms
[2018-07-22T13:18:02.220+0000][19][gc,phases ] GC(1) Pause Relocate Start 9.183ms
[2018-07-22T13:18:02.229+0000][13][gc,phases ] GC(1) Concurrent Relocate 8.888ms
[2018-07-22T13:18:02.229+0000][13][gc,load ] GC(1) Load: 0.09/0.43/0.23
[2018-07-22T13:18:02.229+0000][13][gc,mmu ] GC(1) MMU: 2ms/0.0%, 5ms/0.0%, 10ms/8.2%, 20ms/54.1%, 50ms/79.6%, 100ms/89.8%
[2018-07-22T13:18:02.229+0000][13][gc,marking ] GC(1) Mark: 4 stripe(s), 3 proactive flush(es), 1 terminate flush(es), 1 completion(s), 0 continuation(s)
[2018-07-22T13:18:02.229+0000][13][gc,reloc ] GC(1) Relocation: Successful, 6M relocated
[2018-07-22T13:18:02.229+0000][13][gc,nmethod ] GC(1) NMethods: 572 registered, 0 unregistered
[2018-07-22T13:18:02.229+0000][13][gc,metaspace] GC(1) Metaspace: 22M used, 22M capacity, 23M committed, 24M reserved
[2018-07-22T13:18:02.229+0000][13][gc,ref ] GC(1) Soft: 838 encountered, 0 discovered, 0 enqueued
[2018-07-22T13:18:02.229+0000][13][gc,ref ] GC(1) Weak: 875 encountered, 259 discovered, 154 enqueued
[2018-07-22T13:18:02.229+0000][13][gc,ref ] GC(1) Final: 57 encountered, 46 discovered, 0 enqueued
[2018-07-22T13:18:02.229+0000][13][gc,ref ] GC(1) Phantom: 2544 encountered, 2541 discovered, 2536 enqueued
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Mark Start Mark End Relocate Start Relocate End High Low
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Capacity: 148M (29%) 152M (30%) 152M (30%) 158M (31%) 158M (31%) 148M (29%)
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Reserve: 40M (8%) 40M (8%) 40M (8%) 40M (8%) 40M (8%) 40M (8%)
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Free: 354M (71%) 350M (70%) 350M (70%) 448M (89%) 448M (89%) 344M (69%)
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Used: 108M (22%) 112M (22%) 112M (22%) 14M (3%) 118M (24%) 14M (3%)
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Live: - 6M (1%) 6M (1%) 6M (1%) - -
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Allocated: - 4M (1%) 4M (1%) 14M (3%) - -
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Garbage: - 101M (20%) 101M (20%) 3M (1%) - -
[2018-07-22T13:18:02.229+0000][13][gc,heap ] GC(1) Reclaimed: - - 0M (0%) 98M (20%) - -
[2018-07-22T13:18:02.229+0000][13][gc ] GC(1) Garbage Collection (Warmup) 108M(22%)->14M(3%)
[2018-07-22T13:18:03.670+0000][13][gc,start ] GC(2) Garbage Collection (Warmup)
[2018-07-22T13:18:03.671+0000][19][gc,phases ] GC(2) Pause Mark Start 0.676ms
[2018-07-22T13:18:03.731+0000][13][gc,phases ] GC(2) Concurrent Mark 59.720ms
[2018-07-22T13:18:03.732+0000][19][gc,phases ] GC(2) Pause Mark End 0.344ms
[2018-07-22T13:18:03.733+0000][13][gc,phases ] GC(2) Concurrent Process Non-Strong References 1.265ms
[2018-07-22T13:18:03.733+0000][13][gc,phases ] GC(2) Concurrent Reset Relocation Set 0.151ms
[2018-07-22T13:18:03.733+0000][13][gc,phases ] GC(2) Concurrent Destroy Detached Pages 0.000ms
[2018-07-22T13:18:03.734+0000][13][gc,phases ] GC(2) Concurrent Select Relocation Set 1.317ms
[2018-07-22T13:18:03.735+0000][13][gc,phases ] GC(2) Concurrent Prepare Relocation Set 0.768ms
[2018-07-22T13:18:03.749+0000][19][gc,phases ] GC(2) Pause Relocate Start 13.753ms
[2018-07-22T13:18:03.776+0000][13][gc,phases ] GC(2) Concurrent Relocate 26.811ms
[2018-07-22T13:18:03.776+0000][13][gc,load ] GC(2) Load: 0.33/0.47/0.25
[2018-07-22T13:18:03.776+0000][13][gc,mmu ] GC(2) MMU: 2ms/0.0%, 5ms/0.0%, 10ms/0.0%, 20ms/29.5%, 50ms/71.8%, 100ms/85.2%
[2018-07-22T13:18:03.776+0000][13][gc,marking ] GC(2) Mark: 4 stripe(s), 3 proactive flush(es), 1 terminate flush(es), 0 completion(s), 0 continuation(s)
[2018-07-22T13:18:03.776+0000][13][gc,reloc ] GC(2) Relocation: Successful, 8M relocated
[2018-07-22T13:18:03.776+0000][13][gc,nmethod ] GC(2) NMethods: 1316 registered, 0 unregistered
[2018-07-22T13:18:03.776+0000][13][gc,metaspace] GC(2) Metaspace: 29M used, 29M capacity, 29M committed, 30M reserved
[2018-07-22T13:18:03.776+0000][13][gc,ref ] GC(2) Soft: 1822 encountered, 0 discovered, 0 enqueued
[2018-07-22T13:18:03.776+0000][13][gc,ref ] GC(2) Weak: 1354 encountered, 493 discovered, 51 enqueued
[2018-07-22T13:18:03.776+0000][13][gc,ref ] GC(2) Final: 57 encountered, 0 discovered, 0 enqueued
[2018-07-22T13:18:03.776+0000][13][gc,ref ] GC(2) Phantom: 2712 encountered, 2709 discovered, 2704 enqueued
[2018-07-22T13:18:03.776+0000][13][gc,heap ] GC(2) Mark Start Mark End Relocate Start Relocate End High Low
[2018-07-22T13:18:03.776+0000][13][gc,heap ] GC(2) Capacity: 196M (39%) 198M (39%) 198M (39%) 210M (42%) 210M (42%) 196M (39%)
[2018-07-22T13:18:03.776+0000][13][gc,heap ] GC(2) Reserve: 40M (8%) 40M (8%) 40M (8%) 40M (8%) 40M (8%) 40M (8%)
[2018-07-22T13:18:03.776+0000][13][gc,heap ] GC(2) Free: 306M (61%) 304M (61%) 304M (61%) 436M (87%) 436M (87%) 292M (58%)
[2018-07-22T13:18:03.776+0000][13][gc,heap ] GC(2) Used: 156M (31%) 158M (31%) 158M (31%) 26M (5%) 170M (34%) 26M (5%)
[2018-07-22T13:18:03.776+0000][13][gc,heap ] GC(2) Live: - 12M (3%) 12M (3%) 12M (3%) - -
[2018-07-22T13:18:03.777+0000][13][gc,heap ] GC(2) Allocated: - 2M (0%) 2M (0%) 18M (4%) - -
[2018-07-22T13:18:03.777+0000][13][gc,heap ] GC(2) Garbage: - 143M (29%) 143M (29%) 11M (2%) - -
[2018-07-22T13:18:03.777+0000][13][gc,heap ] GC(2) Reclaimed: - - 0M (0%) 132M (26%) - -
[2018-07-22T13:18:03.777+0000][13][gc ] GC(2) Garbage Collection (Warmup) 156M(31%)->26M(5%)小结
ZGC在如下几个阶段是concurrent的：
- Marking
- Relocation/Compaction
- Relocation Set Selection
- Reference Processing
- JNI WeakRefs Cleaning
doc
- openjdk zgc wiki
- ZGC - Oracle’s Large-Heap Garbage Collector
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