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https://issues.apache.org/jira/browse/HDFS-6782?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14083903#comment-14083903
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Hadoop QA commented on HDFS-6782:
---------------------------------
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12659525/HDFS-6782.002.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. There were no new javadoc warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 2.0.3) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 core tests{color}. The patch passed unit tests in
hadoop-hdfs-project/hadoop-hdfs.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-HDFS-Build/7545//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/7545//console
This message is automatically generated.
> Improve FS editlog logSync
> --------------------------
>
> Key: HDFS-6782
> URL: https://issues.apache.org/jira/browse/HDFS-6782
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 2.4.1
> Reporter: Yi Liu
> Assignee: Yi Liu
> Attachments: HDFS-6782.001.patch, HDFS-6782.002.patch
>
>
> In NN, it uses a double buffer (bufCurrent, bufReady) for log sync,
> bufCurrent it to buffer new coming edit ops and bufReady is for flushing.
> This's efficient. When flush is ongoing, and bufCurrent is full, NN goes to
> force log sync, and all new Ops are blocked (since force log sync is
> protected by FSNameSystem write lock). After the flush finished, the new Ops
> are still blocked, but actually at this time, bufCurrent is free and Ops can
> go ahead and write to the buffer. The following diagram shows the detail.
> This JIRA is for this improvement. Thanks [~umamaheswararao] for confirming
> this issue.
> {code}
> edit1(txid1) ------ write to bufCurrent -------- logSync --------- (swap
> buffer)flushing -------
> edit2(txid2) ------ write to bufCurrent -------- logSync --------- waiting
> -------
> edit3(txid3) ------ write to bufCurrent -------- logSync --------- waiting
> -------
> edit4(txid4) ------ write to bufCurrent -------- logSync --------- waiting
> -------
> edit5(txid5) ------ write to bufCurrent --full-- force sync --------- waiting
> -------
> edit6(txid6) ------ blocked
> ...
> editn(txidn) ------ blocked
> {code}
> After the flush, it becomes
> {code}
> edit1(txid1) ------ write to bufCurrent -------- logSync --------- finished
> --------
> edit2(txid2) ------ write to bufCurrent -------- logSync --------- flushing
> -------
> edit3(txid3) ------ write to bufCurrent -------- logSync --------- waiting
> -------
> edit4(txid4) ------ write to bufCurrent -------- logSync --------- waiting
> -------
> edit5(txid5) ------ write to bufCurrent --full-- force sync --------- waiting
> -------
> edit6(txid6) ------ blocked
> ...
> editn(txidn) ------ blocked
> {code}
> After edit1 finished, bufCurrent is free, and the thread which flushes txid2
> will also flushes txid3-5, so we should return from the force sync of edit5
> and FSNamesystem write lock will be freed (Don't worry that edit5 Op will
> return, since there will be a normal logSync after the force logSync and
> there will wait for sync finished). This is the idea of this JIRA.
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