with no data. ● Less fragment(Allocate 2MB one time) , Less Mixed GC. ● JVM will never free BucketCache’s byte buffer. ● But JVM will still sweep the buffer and compact them. (old generation) BucketCache no data. After GC (G1) bucket-4KB (2MB) bucket-8KB (2MB) bucket-16KB (2MB) bucket-32KB (2MB) ● JVM will NOT sweep the cache and compacting them (old generation) ● Less mixed GC(s) and shorter STW time

an offheap read and write path. The KV are allocated from the JVM offheap, and the memory area in offheap won’t be garbage collected by JVM, so upstreams need to deallocate the memory explicitly by themself refCnt, once release the HFileBlock, if decreasing to zero, then just do nothing and wait for the JVM Garbage Collection. The block eviction in BucketCache also won’t impact the HFileBlocks in RPC. So

1000 bytes ● Pressure test for G1GC tuning ○ 40 write clients + 20 read clients ○ 1 hour for each JVM option changed ● HBase configuration ○ 0.3 <= global memstore limit <= 0.45 ○ hfile.block.cache 24 Core ● DISK: 4T x 12 HDD ● Network Interface: 10Gb/s 5 Region Server HBase Cluster Initial JVM Options -Xmx30g -Xms30g -XX:MaxDirectMemorySize=30g -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions