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https://issues.apache.org/jira/browse/HADOOP-17362?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17227693#comment-17227693
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Ahmed Hussein commented on HADOOP-17362:
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[~daryn] did a quick evaluation of the performance :
{quote}Given a real world har for 1 hour of tez jobs from:
listing formerly took 12s with ~47.5k rpcs, reduced to 6s with 10 rpcs
globbing killed after 11min with hundreds of thousands of rpcs with 16G heap,
reduced to 11s with 10 rpcs and 768M heap{quote}
> Doing hadoop ls on Har file triggers too many RPC calls
> -------------------------------------------------------
>
> Key: HADOOP-17362
> URL: https://issues.apache.org/jira/browse/HADOOP-17362
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs
> Reporter: Ahmed Hussein
> Assignee: Ahmed Hussein
> Priority: Major
> Labels: pull-request-available
> Time Spent: 20m
> Remaining Estimate: 0h
>
> [~daryn] has noticed that Invoking hadoop ls on HAR is taking too much of
> time.
> The har system has multiple deficiencies that significantly impacted
> performance:
> # Parsing the master index references ranges within the archive index. Each
> range required re-opening the hdfs input stream and seeking to the same
> location where it previously stopped.
> # Listing a har stats the archive index for every "directory". The per-call
> cache used a unique key for each stat, rendering the cache useless and
> significantly increasing memory pressure.
> # Determining the children of a directory scans the entire archive contents
> and filters out children. The cached metadata already stores the exact child
> list.
> # Globbing a har's contents resulted in unnecessary stats for every leaf path.
>
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