01 機(jī)器內(nèi)存告警球散，查看jvm內(nèi)存及gc情況
老年代占比接近90%
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT
45.24 0.00 70.10 89.96 90.22 84.81 2482 107.995 3 2.037 110.032
45.24 0.00 70.45 89.96 90.22 84.81 2482 107.995 3 2.037 110.032
45.24 0.00 70.73 89.96 90.22 84.81 2482 107.995 3 2.037 110.032
45.24 0.00 71.05 89.96 90.22 84.81 2482 107.995 3 2.037 110.032
45.24 0.00 71.23 89.96 90.22 84.81 2482 107.995 3 2.037 110.032`
02 手動觸發(fā)一次fullGC后繼續(xù)統(tǒng)計
發(fā)現(xiàn)老年代占比下降到了5%左右
疑惑多次yanggc回收不掉的對象漏到老年代之后，為啥能被一次fullgc回收散庶？判斷一個對象能否被回收的算法應(yīng)該都是根搜索法呀蕉堰，沒道理漏到老年代之后引用都失效。推測跟gc收集器特點(diǎn)有關(guān)——yanggc使用的是Parallel Scavenge悲龟，該收集器關(guān)注的是系統(tǒng)的吞吐量屋讶；也就是說其實(shí)yanggc判斷對象也是可以回收的，但是為了滿足系統(tǒng)預(yù)設(shè)的吞吐量须教，沒有回收這些對象皿渗。
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT
45.24 0.00 71.05 89.96 90.22 84.81 2482 107.995 3 2.037 110.032
45.24 0.00 71.23 89.96 90.22 84.81 2482 107.995 3 2.037 110.032
0.00 23.12 0.00 89.98 90.22 84.81 2483 108.031 4 2.037 110.068
0.00 0.00 0.41 5.75 90.00 84.44 2483 108.031 4 2.477 110.507
0.00 0.00 0.73 5.75 90.00 84.44 2483 108.031 4 2.477 110.507
03 對比fullGC前后heap的使用情況
fullGC前
using thread-local object allocation.
Parallel GC with 8 thread(s)
Heap Configuration:
MinHeapFreeRatio = 0
MaxHeapFreeRatio = 100
MaxHeapSize = 4294967296 (4096.0MB)
NewSize = 1431306240 (1365.0MB)
MaxNewSize = 1431306240 (1365.0MB)
OldSize = 2863661056 (2731.0MB)
NewRatio = 2
SurvivorRatio = 8
MetaspaceSize = 536870912 (512.0MB)
CompressedClassSpaceSize = 1073741824 (1024.0MB)
MaxMetaspaceSize = 2147483648 (2048.0MB)
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:
capacity = 1371013120 (1307.5MB)
used = 1357456104 (1294.5710220336914MB)
free = 13557016 (12.928977966308594MB)
99.01116803316951% used
From Space:
capacity = 30932992 (29.5MB)
used = 12337216 (11.76568603515625MB)
free = 18595776 (17.73431396484375MB)
39.88368147510593% used
To Space:
capacity = 29360128 (28.0MB)
used = 0 (0.0MB)
free = 29360128 (28.0MB)
0.0% used
PS Old Generation
capacity = 2863661056 (2731.0MB)
used = 2856853056 (2724.5073852539062MB)
free = 6808000 (6.49261474609375MB)
99.76226236740777% used
49437 interned Strings occupying 5198632 bytes.
fullGC后
Heap Configuration:
MinHeapFreeRatio = 0
MaxHeapFreeRatio = 100
MaxHeapSize = 4294967296 (4096.0MB)
NewSize = 1431306240 (1365.0MB)
MaxNewSize = 1431306240 (1365.0MB)
OldSize = 2863661056 (2731.0MB)
NewRatio = 2
SurvivorRatio = 8
MetaspaceSize = 536870912 (512.0MB)
CompressedClassSpaceSize = 1073741824 (1024.0MB)
MaxMetaspaceSize = 2147483648 (2048.0MB)
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:
capacity = 1380450304 (1316.5MB)
used = 692010592 (659.9527282714844MB)
free = 688439712 (656.5472717285156MB)
50.129337506379365% used
From Space:
capacity = 25165824 (24.0MB)
used = 0 (0.0MB)
free = 25165824 (24.0MB)
0.0% used
To Space:
capacity = 24117248 (23.0MB)
used = 0 (0.0MB)
free = 24117248 (23.0MB)
0.0% used
PS Old Generation
capacity = 2863661056 (2731.0MB)
used = 208333416 (198.6822280883789MB)
free = 2655327640 (2532.317771911621MB)
7.275072430918305% used
48278 interned Strings occupying 5113608 bytes.
發(fā)現(xiàn)年輕代斩芭、老年代均有大量對象被回收，但是年輕代還有將近700M乐疆、來年代還有將近200M划乖。
04 殺了個dump看看
發(fā)現(xiàn)大量占用內(nèi)存的對象跟公司rpc框架有關(guān)，排查代碼挤土，發(fā)現(xiàn)rpc失敗后琴庵，存在內(nèi)存泄漏的風(fēng)險。后面有時間寫文章分享
