Dmitry Konstantinov created CASSANDRA-20173:
-----------------------------------------------
Summary: Avoid new ByteBuffer allocation for each NativeCell
during flushing of offheap_objects memtable
Key: CASSANDRA-20173
URL: https://issues.apache.org/jira/browse/CASSANDRA-20173
Project: Apache Cassandra
Issue Type: Improvement
Components: Local/Memtable
Reporter: Dmitry Konstantinov
Assignee: Dmitry Konstantinov
Attachments: image-2024-12-29-13-06-13-115.png
Currently for memtable_allocation_type: offheap_objects when we flush a
memtable we allocate new ByteBuffer object for each NativeCell to write it to
disk. It is one of the main contributors (together with CASSANDRA-20162) to
memory allocation for MemtableFlushWriter thread:
!image-2024-12-29-13-06-13-115.png|width=570!
Instead of retrieving of the value() as ByteBuffer we can introduce
NativeValueAccessor to not expose ByteBuffer + keep it inside NativeCell as a
thread-local to re-use.
Note: for Cassandra 4.x the situation is even because we clone very BTreeRow
from off-heap to heap due to using the same iterator as for usual reads (where
we need to protect against memtable lifecycle changes). In case of flushing
such protection is not needed. For TrieMemtable we skip such cloning
(CASSANDRA-17240,
[https://github.com/apache/cassandra/blob/cassandra-5.0/src/java/org/apache/cassandra/db/memtable/TrieMemtable.java#L393]).
It makes sense to consider such skipping for over types of memtable too..
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
