Mailing-List: contact issues-help@hbase.apache.org; run by ezmlm
Precedence: bulk
Date: Wed, 2 Feb 2011 05:55:29 +0000 (UTC)
From: "stack (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: 
 <943874318.4477.1296626129020.JavaMail.tomcat@hel.zones.apache.org>
In-Reply-To: <7608788.86351295546983949.JavaMail.jira@thor>
Subject: [jira] Commented: (HBASE-3455) Heap fragmentation in region server
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HBASE-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12989524#comment-12989524 ] 

stack commented on HBASE-3455:
------------------------------

+1

Minors below:

On commit, I wonder if you should commit w/ it disabled on branch but enabled on trunk?

In here:
{code}
+    // Use the internalAdd method here since we (a) already have a lock
+    // and (b) cannot safely use the MSLAB here.
+    // See TestMemStore.DISABLED_testUpsertMSLAB
{code}

... its not safe because it would bloat memory?  Or is it some thread 'safety' issue?  Maybe clarify on commit?

Should this class even be public?

+public class MemStoreLAB {

Why this?

{code}
+    if (size > maxAlloc) {
+      return new Allocation(new byte[size], 0);
+    }
{code}

On return we'll clone when we don't need to?  Return null as flag that we're not to clone?  (Caller is maybeCloneWithAllocator).

We should open new issue for fixing upsert?


> Heap fragmentation in region server
> -----------------------------------
>
>                 Key: HBASE-3455
>                 URL: https://issues.apache.org/jira/browse/HBASE-3455
>             Project: HBase
>          Issue Type: Brainstorming
>          Components: performance, regionserver
>    Affects Versions: 0.90.1
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.90.1
>
>         Attachments: HBasefragmentation.pdf, collapse-arrays.patch, icv-frag.png, mslab-1.txt, mslab-2.txt, mslab-3.txt, mslab-4.txt, mslab-5.txt, parse-fls-statistics.py, with-kvallocs.png
>
>
> Stop-the-world GC pauses have long been a problem in HBase. "Concurrent mode failures" can usually be tuned around by setting the initiating occupancy fraction low, but eventually the heap becomes fragmented and a promotion failure occurs.
> This JIRA is to do research/experiments about the heap fragmentation issue and possible solutions.

-- 
This message is automatically generated by JIRA.
-
For more information on JIRA, see: http://www.atlassian.com/software/jira