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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15506) FSDataOutputStream.write() allocates new byte buffer on each operation
Date Mon, 28 Mar 2016 06:10:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15506?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15213853#comment-15213853

Lars Hofhansl commented on HBASE-15506:

Let's be careful, please. Many times when one tries to be smarter than the GC it backfires
(false lifetimes of reused objects, etc). Allocating stuff on the heap is not necessary bad
by itself. That's what the heap for. :)

It's only bad when there's a _measurable_ performance impact (including long GC pauses)...
Or if the allocation is strictly unnecessary.

Which of the two option is using more memory bandwidth? That's the metric I'd be interested

In any case, does this hold for G1 as well?

It's possible I am missing something. We're talking about 64KB buffers allocating for the
HDFS stream packets, right? 100MB of garbage in 64KB chunks is a mere 1600 objects. Surely
we're not going to be worried about that.

Are compactions or HFileWriter doing something stupid?

Since there is fix in HDFS-7276, I clearly must be missing something. But what is that?

> FSDataOutputStream.write() allocates new byte buffer on each operation
> ----------------------------------------------------------------------
>                 Key: HBASE-15506
>                 URL: https://issues.apache.org/jira/browse/HBASE-15506
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Vladimir Rodionov
>            Assignee: Vladimir Rodionov
> Deep inside stack trace in DFSOutputStream.createPacket.
> This should be opened in HDFS. This JIRA is to track HDFS work.

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