1. 使用jcmd
假設java進程id爲1000
# Linux
jcmd 1000 PerfCounter.print |grep gc.collector.*name
# Windows
jcmd 1000 PerfCounter.print |findstr gc.collector.*name
以串行收集器(-XX:+UseSerialGC )爲例，返回信息如下：
sun.gc.collector.0.name="Copy"
sun.gc.collector.1.name="MSC"
名稱與收集器對照表
| 名稱 | 收集器 | 作用區域 | 啓用參數 |
|---|---|---|---|
| Copy | Serial | Young | -XX:+UseSerialGC |
| MSC | Serial Old | Old | -XX:+UseSerialGC |
| PSScavenge | Parallel Scavenge | Young | -XX:+UseParallelGC |
| PSMarkSweep | Parallel Scavenge | Old | -XX:+UseParallelGC -XX:-UseParallelOldGC |
| PSParallelCompact | Parallel Old | Old | -XX:+UseParallelGC |
| PCopy | ParNew | Young | -XX:+UseConcMarkSweepGC 或者 -XX:+UseParNewGC(JDK9起廢除) |
| CMS | Concurrent Mark Sweep | Old | -XX:+UseConcMarkSweepGC (JDK9起標識爲過期，由G1接班) |
| G1 incremental collections | G1 | Young或者Young+部分Old | -XX:+UseG1GC(JDK9起默認收集器) |
| G1 stop-the-world full collections | G1 | Full | -XX:+UseG1GC |
各Java版本默認收集器
| 版本 | Young | Old |
|---|---|---|
| JDK6 | PSScavenge(Parallel Scavenge) | PSMarkSweep (Parallel Scavenge) |
| JDK7 | PSScavenge(Parallel Scavenge) | PSParallelCompact(Parallel Old) |
| JDK8 | PSScavenge(Parallel Scavenge) | PSParallelCompact(Parallel Old) |
| JDK11 | G1 | G1 |
從G1開始分代回收漸漸模糊，最新的ZGC已經沒有分代(可能只是暫時的)一說。