HBASE-21879 Read HFile ’s Block into ByteBuffer directly. 1. Background For reducing the Java GC impact to p99/p999 RPC latency, HBase 2.x has made an offheap read and write path. The KV are allocated Similarly, on the read path, we’ll try to read the BucketCache firstly, if the Cache misses, go to the HFile and read the corresponding block. The workflow: reading block from cache OR sending cells to client there should be rarely heap allocation. However, we found that the process of reading the Block from HFile is still copied to the heap firstly, the heap block won’t free unless the WriterThread of BucketCache

Abstract In Server Side ❏ High Efficiency ❏ Query Diversity ❏ Server Resource Protection HFile Response Result HFile Block-2 Block-1 Two Cases Put-1 Delete-1 Delete-2 Delete-999 …. …. Block-100 Put-2000 Response Result Put-1 Put-2000 scan.setFilter(new SingleColumnValueFilter(...)) Scan the HFile with so many deletes Read too many block data into memory, which may cause GC or OOM Server Side

hour for each JVM option changed ● HBase configuration ○ 0.3 <= global memstore limit <= 0.45 ○ hfile.block.cache.size = 0.1 ○ hbase.hregion.memstore.flush.size = 256 MB ○ hbase.bucketcache.ioengine

root.u.value32 = pMap->root; data.handle.type = VMMDevHGCMParmType_64bit; data.handle.u.value64 = hFile; data.offset.type = VMMDevHGCMParmType_64bit; data.offset.u.value64 = offset; data.cb.type = VM

root.u.value32 = pMap->root; data.handle.type = VMMDevHGCMParmType_64bit; data.handle.u.value64 = hFile; data.offset.type = VMMDevHGCMParmType_64bit; data.offset.u.value64 = offset; data.cb.type = VM

root.u.value32 = pMap->root; data.handle.type = VMMDevHGCMParmType_64bit; data.handle.u.value64 = hFile; data.offset.type = VMMDevHGCMParmType_64bit; data.offset.u.value64 = offset; data.cb.type = VM

root.u.value32 = pMap->root; data.handle.type = VMMDevHGCMParmType_64bit; data.handle.u.value64 = hFile; data.offset.type = VMMDevHGCMParmType_64bit; data.offset.u.value64 = offset; data.cb.type = VM

root.u.value32 = pMap->root; data.handle.type = VMMDevHGCMParmType_64bit; data.handle.u.value64 = hFile; data.offset.type = VMMDevHGCMParmType_64bit; data.offset.u.value64 = offset; data.cb.type = VMMD

root.u.value32 = pMap->root; data.handle.type = VMMDevHGCMParmType_64bit; data.handle.u.value64 = hFile; data.offset.type = VMMDevHGCMParmType_64bit; data.offset.u.value64 = offset; data.cb.type = VM

root.u.value32 = pMap->root; data.handle.type = VMMDevHGCMParmType_64bit; data.handle.u.value64 = hFile; data.offset.type = VMMDevHGCMParmType_64bit; data.offset.u.value64 = offset; data.cb.type = VMMD