[HDFS-8900] Compact XAttrs to optimize memory footprint.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.8.0, 3.0.0-alpha1
• Component/s: namenode
• Target Version/s: 2.8.0
• Hadoop Flags: Incompatible change, Reviewed
• Release Note: The config key "dfs.namenode.fs-limits.max-xattr-size" can no longer be set to a value of 0 (previously used to indicate unlimited) or a value greater than 32KB. This is a constraint on xattr size similar to many local filesystems.
• Assignee: Yi Liu
• Reporter: Yi Liu
• Created: 17/Aug/15 05:53
• Updated: 30/Aug/16 01:29
• Resolved: 25/Aug/15 08:25

Description

private final ImmutableList<XAttr> xAttrs;

Currently we use above in XAttrFeature, it's not efficient from memory point of view, since ImmutableList and XAttr have object memory overhead, and each object has memory alignment.

We can use a byte[] in XAttrFeature and do some compact in XAttr.

Issue Links

• breaks: HDFS-8963 Fix incorrect sign extension of xattr length in HDFS-8900