[HBASE-15786] Create DBB backed MSLAB pool

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.0
• Component/s: regionserver
• Hadoop Flags: Reviewed

Release Note

Added a new config hbase.regionserver.offheap.global.memstore.size using which one can specify the global off heap limit that all memstores can use. When this config is in MSLAB should be turned ON and we will use the entire size for the MSLAB pool. It will make off heap chunks and pool then. It will behave as if we are working with off heap memstores. When this config is having a valid value and MSLAB is turned OFF, the system will just ignore the offheap size and continue to use global max heap space % for memstores and work with on heap memstores.

• Assignee: Anoop Sam John
• Reporter: ramkrishna.s.vasudevan
• Created: 06/May/16 12:15
• Updated: 01/Jul/22 21:33
• Resolved: 24/Nov/16 15:18

Description

We can make use of MSLAB pool for this off heap memstore.
Right now one can specify the global memstore size (heap size) as a % of max memory using a config. We will add another config with which one can specify the global off heap memstore size. This will be exact size not as %. When off heap memstore in use, we will give this entire area for the MSLAB pool and that will create off heap chunks. So when cells are added to memstore, the cell data gets copied into the off heap MSLAB chunk spaces. Note that when the pool size is not really enough and we need additional chunk creation, we wont use off heap area for that. We dony want to create so many on demand DBBs.