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Daniel Templeton commented on HDFS-8873: ---------------------------------------- Oops, forgot to address the ThrottleTask comment: bq. ThrottleTask / UnthrottleTask: is there any way we could reuse these objects and avoid generating all that garbage? Sure. :) > throttle directoryScanner > ------------------------- > > Key: HDFS-8873 > URL: https://issues.apache.org/jira/browse/HDFS-8873 > Project: Hadoop HDFS > Issue Type: Improvement > Components: datanode > Affects Versions: 2.7.1 > Reporter: Nathan Roberts > Assignee: Daniel Templeton > Attachments: HDFS-8873.001.patch, HDFS-8873.002.patch, > HDFS-8873.003.patch > > > The new 2-level directory layout can make directory scans expensive in terms > of disk seeks (see HDFS-8791) for details. > It would be good if the directoryScanner() had a configurable duty cycle that > would reduce its impact on disk performance (much like the approach in > HDFS-8617). > Without such a throttle, disks can go 100% busy for many minutes at a time > (assuming the common case of all inodes in cache but no directory blocks > cached, 64K seeks are required for full directory listing which translates to > 655 seconds) -- This message was sent by Atlassian JIRA (v6.3.4#6332)