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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-3483) No soft flush trigger on global memstore limit
Date Mon, 31 Jan 2011 22:05:29 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3483?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12988918#comment-12988918
] 

stack commented on HBASE-3483:
------------------------------

+1 on commit.

What changed here? Tab for spaces?

{code}
-  private final Map<HRegion, FlushQueueEntry> regionsInQueue =
-    new HashMap<HRegion, FlushQueueEntry>();
+  private final Map<HRegion, FlushRegionEntry> regionsInQueue =
+    new HashMap<HRegion, FlushRegionEntry>();
+  private AtomicBoolean wakeupPending = new AtomicBoolean();
{code}

> No soft flush trigger on global memstore limit
> ----------------------------------------------
>
>                 Key: HBASE-3483
>                 URL: https://issues.apache.org/jira/browse/HBASE-3483
>             Project: HBase
>          Issue Type: Bug
>          Components: performance, regionserver
>    Affects Versions: 0.90.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.90.1
>
>         Attachments: hbase-3483.txt, hbase-3483.txt
>
>
> I think this is the reason people see long blocking periods under write load.
> Currently when we hit the global memstore limit, we call reclaimMemStoreMemory() which
is synchronized - thus everyone has to wait until the memory has flushed down to the low water
mark. This causes every writer to block for 10-15 seconds on a large heap.
> Instead we should start triggering flushes (in another thread) whenever we're above the
low water mark. Then only block writers when we're above the high water mark.

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