垃圾收集器

• 2019 年 10 月 3 日
• 笔记

JVM(?)??????

??????????????????????????????????????——????????????

??

???????????????????????????? HotSpot????? 7????????????????????????????

Serial

Serial????????????????????"Stop The World"???????????????????????????????????????????????????????

ParNew

ParNew ???? Serial ???????????????????????????? Serial ?????????Stop The World ?????????????????

Parallel Scavenge

Parallel Scavenge ?????? ParNew ?????????????????????? ??????????????? CPU ???????????? CPU ?????????? ??? = ???????? / (???????? + ??????)?????????????? CPU ?????????????????????????????????

Serial Old

?? Serial ???????????? Serial ????????

Parallel Old

?? Parallel Scavenge ?????????? Parallel Scavenge ?????? ????? ??????

CMS

CMS???? Concurrent Mark Sweep????????????????????????

1. ????
2. ????
3. ????
4. ????

??????????? GC Roots ???????????????????????? GC Roots Tracing??????????????????????????????????????????????????

???????????????????? Stop The World? ???????????????????????????????????????????????????

?CMS??????????????????????

???????? GC ?? 4???????????????????? ???? ???????????????????????????????????????????????????????????

??????????????? JVM ???????????????????????????????????????????? "Concurrent Mode Failure" ????? JVM ????????Serial Old???????????????????????????????? Full GC??????

??????????????????????????????????????? ??-???? ?????????????????

???? CMS ?????????????????????????? CPU ??????????????????????????????????????????

G1

Garbage-First ????????????????????????——Region????????????,??????????,?????region?????

?????????G1 ????? ????????????? Region ???????????????????????????????????????? ????????????????? Region????????? GC ?????????

??????????? Region ?????????????????? Region ????????????

????Region ??????????????????? Region ?????????????????????????????????????????? ???? ???????????????????

?? G1 ??? Remembered Set ???????????? Reference ??????????,?????? Write Barrier ??????????? Reference ??????????? Region ????????? CardTable ?????????????? Region ? Remembered Set ?????????????????????? Remembered Set ??????????????????

G1 ??????????

1. ????
2. ????
3. ????
4. ????

?????G1 ?? 3???? CMS ?????????????????

??????????G1 ? CMS ?????????? GC Roots ???????????????? TAMS?Next Top at Mark Start??????????????????????????? Region ????????????? CMS ?????????????????? Remembered Set Log ?????????,? Remembered Set Log ??? Remembered Set ?????????????? ?? Region ?????????????????????????????

GC ????

??

?????????????????? Hotspot ???? 7??????????????????????????????????????????????

???????????????????????????????????????????????????????

?????? “iceWang" ???????????????????????????????????????????

??????????????? JavaWeb ??????????? Java ???-JVM???????????