[
https://issues.apache.org/jira/browse/HADOOP-12475?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14959815#comment-14959815
]
Sangjin Lee commented on HADOOP-12475:
--------------------------------------
Thanks [~cnauroth]!
I'm actually somewhat confused by this. When we commit a patch onto trunk, do
we add the attribution to the trunk section or the latest unreleased major
release (in this case 2.8.0)? I see a whole bunch of JIRAs in both sections,
and I assumed that I would add it to the trunk section for trunk and 2.8.0 for
branch-2. The commit guide doesn't seem to mention it clearly either...
> Replace guava Cache with ConcurrentHashMap for caching Connection in ipc
> Client
> -------------------------------------------------------------------------------
>
> Key: HADOOP-12475
> URL: https://issues.apache.org/jira/browse/HADOOP-12475
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: conf, io, ipc
> Reporter: Walter Su
> Assignee: Walter Su
> Fix For: 2.8.0
>
> Attachments: HADOOP-12475.01.patch, HADOOP-12475.02.patch,
> HADOOP-12475.03.patch
>
>
> quote [~daryn] from HADOOP-11772:
> {quote}
> CacheBuilder is obscenely expensive for concurrent map, and it requires
> generating unnecessary garbage even just to look up a key. Replace it with
> ConcurrentHashMap.
> I identified this issue that impaired my own perf testing under load. The
> slowdown isn't just the sync. It's the expensive of Connection's ctor
> stalling other connections. The expensive of ConnectionId#equals causes
> delays. Synch'ing on connections causes unfair contention unlike a sync'ed
> method. Concurrency simply hides this.
> {quote}
> BTW, guava Cache is heavyweight. Per local test, ConcurrentHashMap has better
> overal performance.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
