[HBASE-13578] Remove Arrays.asList().subList() from FSHLog.offer()

• Type: Improvement
• Status: Closed
• Priority: Trivial
• Resolution: Fixed
• Affects Version/s: 1.0.0, 1.1.0, 2.0.0
• Fix Version/s: 1.1.0, 2.0.0
• Component/s: wal
• Assignee: Matteo Bertozzi
• Reporter: Matteo Bertozzi
• Created: 28/Apr/15 10:31
• Updated: 04/Jul/15 12:50
• Resolved: 28/Apr/15 20:52

Description

while doing a run with a profiler I noticed this:

FSHLog.java
void offer(final long sequence, final SyncFuture [] syncFutures, final int syncFutureCount) {
  ...
  this.syncFutures.addAll(Arrays.asList(syncFutures).subList(0, syncFutureCount));
}

it is creating an Arrays.ArrayList then a RandomAccessSubList,
and then addAll() is using creating an iterator and call the syncFutures.add() for each item.

a simpler for loop adding the items directly is not too ugly and it will avoid all this stuff.
I've attached a simple test to compare the two, it will not make huge difference but since we are in the core path any tiny bit probably helps.