[
https://issues.apache.org/jira/browse/HBASE-13819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16279306#comment-16279306
]
huaxiang sun commented on HBASE-13819:
--------------------------------------
Hi [~anoop.hbase], I am reading the patch and thought about one corner case
that could bring in dm exhaustion.
Right now, putBuffer() does not free DM it allocates. It has to wait for
ByteBuffer to be GCed and then the cleaner chore to free the DM.
In some extreme cases, this could result in the DM exhaustion as it will take
some time for DM to be freed to system.
Is it possible to free the DM immediately if it is not going to be cached in
the pool? (similar to JDK-8147468).
Googled the internet,
https://stackoverflow.com/questions/8462200/examples-of-forcing-freeing-of-native-memory-direct-bytebuffer-has-allocated-us
> Make RPC layer CellBlock buffer a DirectByteBuffer
> --------------------------------------------------
>
> Key: HBASE-13819
> URL: https://issues.apache.org/jira/browse/HBASE-13819
> Project: HBase
> Issue Type: Sub-task
> Components: Scanners
> Reporter: Anoop Sam John
> Assignee: Anoop Sam John
> Fix For: 2.0.0, 1.3.0
>
> Attachments: HBASE-13819.patch, HBASE-13819_branch-1.patch,
> HBASE-13819_branch-1.patch, HBASE-13819_branch-1.patch, q.png
>
>
> In RPC layer, when we make a cellBlock to put as RPC payload, we will make an
> on heap byte buffer (via BoundedByteBufferPool). The pool will keep upto
> certain number of buffers. This jira aims at testing possibility for making
> this buffers off heap ones. (DBB) The advantages
> 1. Unsafe based writes to off heap is faster than that to on heap. Now we are
> not using unsafe based writes at all. Even if we add, DBB will be better
> 2. When Cells are backed by off heap (HBASE-11425) off heap to off heap
> writes will be better
> 3. When checked the code in SocketChannel impl, if we pass a HeapByteBuffer
> to the socket channel, it will create a temp DBB and copy data to there and
> only DBBs will be moved to Sockets. If we make DBB 1st hand itself, we can
> avoid this one more level of copying.
> Will do different perf testing with changed and report back.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
