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https://issues.apache.org/jira/browse/TAJO-548?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13894807#comment-13894807
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Hyunsik Choi commented on TAJO-548:
-----------------------------------
Created a review request against branch master in reviewboard
https://reviews.apache.org/r/17852/
> Investigate frequent young gc
> ------------------------------
>
> Key: TAJO-548
> URL: https://issues.apache.org/jira/browse/TAJO-548
> Project: Tajo
> Issue Type: Improvement
> Affects Versions: 0.8-incubating
> Reporter: Min Zhou
> Assignee: Min Zhou
> Attachments: TAJO-548-v2.patch, TAJO-548.patch
>
>
> Two days ago, I ran a 300X TPCH Q1 on a 7 slaves , 1 master tajo clsuter.
> Here is my configuration for each worker jvm
> {noformat}
> export TAJO_WORKER_OPTS="-Xmx20g -Xms20g -XX:MaxPermSize=512m -verbose:gc
> -Xloggc:$TAJO_LOG_DIR/worker-gc.log -XX:+UseConcMarkSweepGC
> -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseCompressedOops "
> {noformat}
> I observed very frequent young gc
> {noformat}
> $ jstat -gcutil `pgrep -f TajoWorker` 1000
> S0 S1 E O P YGC YGCT FGC FGCT GCT
> 0.00 2.13 57.40 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.40 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.41 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.42 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.42 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.43 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.43 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.43 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.43 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.43 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.44 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.53 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.57 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.58 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.58 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.58 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.59 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.59 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.60 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 57.60 3.79 99.65 5185 75.042 0 0.000 75.042
> 0.00 2.13 66.73 3.79 99.66 5185 75.042 0 0.000 75.042
> 0.00 66.46 17.89 3.79 99.66 5190 75.082 0 0.000 75.082
> 8.79 0.00 37.36 3.88 99.66 5202 75.533 0 0.000 75.533
> 0.00 9.10 21.61 3.88 99.66 5216 75.926 0 0.000 75.926
> ...
> 105.523
> {noformat}
> After finish the Q1 query, GCT is at 105.523, which means young gc cost 30
> seconds. As well known, ParNew YGC is a kind of stop the world gc. The
> whole query need about 98 secs. So in this case, young gc waste nearly 1
> third of the query time.
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