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https://issues.apache.org/jira/browse/HDFS-16000?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Xiangyi Zhu updated HDFS-16000:
-------------------------------
Description:
It takes a long time to move a large directory with rename. For example, it
takes about 40 seconds to move a 1000W directory. When a large amount of data
is deleted to the trash, the move large directory will occur when the recycle
bin makes checkpoint. In addition, the user may also actively trigger the move
large directory operation, which will cause the NameNode to lock too long and
be killed by Zkfc. Through the flame graph, it is found that the main time
consuming is to create the EnumCounters object.
h3. Rename logic optimization:
* Regardless of whether the rename operation is the source directory and the
target directory, the quota count must be calculated three times. The first
time, check whether the moved directory exceeds the target directory quota, the
second time, calculate the mobile directory quota to update the source
directory quota, and the third time, calculate the mobile directory
configuration update to the target directory.
* I think some of the above three quota quota calculations are unnecessary.
For example, if all parent directories of the source directory and target
directory are not configured with quota, there is no need to calculate
quotaCount. Even if both the source directory and the target directory use
quota, there is no need to calculate the quota three times. The calculation
logic for the first and third times is the same, and it only needs to be
calculated once.
was:
It takes a long time to move a large directory with rename. For example, it
takes about 40 seconds to move a 1000W directory. When a large amount of data
is deleted to the trash, the move large directory will occur when the recycle
bin makes checkpoint. In addition, the user may also actively trigger the move
large directory operation, which will cause the NameNode to lock too long and
be killed by Zkfc. Through the flame graph, it is found that the main time
consuming is to create the EnumCounters object.
h3. I think the following two points can optimize the efficiency of rename
execution
h3. QuotaCount calculation time-consuming optimization:
* Create a QuotaCounts object in the calculation directory quotaCount, and
pass the quotaCount to the next calculation function through a parameter each
time, so as to avoid creating an EnumCounters object for each calculation.
* In addition, through the flame graph, it is found that using lambda to
modify QuotaCounts takes longer than the ordinary method, so the ordinary
method is used to modify the QuotaCounts count.
h3. Rename logic optimization:
* Regardless of whether the rename operation is the source directory and the
target directory, the quota count must be calculated three times. The first
time, check whether the moved directory exceeds the target directory quota, the
second time, calculate the mobile directory quota to update the source
directory quota, and the third time, calculate the mobile directory
configuration update to the target directory.
* I think some of the above three quota quota calculations are unnecessary.
For example, if all parent directories of the source directory and target
directory are not configured with quota, there is no need to calculate
quotaCount. Even if both the source directory and the target directory use
quota, there is no need to calculate the quota three times. The calculation
logic for the first and third times is the same, and it only needs to be
calculated once.
> HDFS : Rename performance optimization
> --------------------------------------
>
> Key: HDFS-16000
> URL: https://issues.apache.org/jira/browse/HDFS-16000
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs, namenode
> Affects Versions: 3.1.4, 3.3.1
> Reporter: Xiangyi Zhu
> Assignee: Xiangyi Zhu
> Priority: Major
> Labels: pull-request-available
> Attachments: 20210428-143238.svg, 20210428-171635-lambda.svg,
> HDFS-16000.patch
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> It takes a long time to move a large directory with rename. For example, it
> takes about 40 seconds to move a 1000W directory. When a large amount of data
> is deleted to the trash, the move large directory will occur when the recycle
> bin makes checkpoint. In addition, the user may also actively trigger the
> move large directory operation, which will cause the NameNode to lock too
> long and be killed by Zkfc. Through the flame graph, it is found that the
> main time consuming is to create the EnumCounters object.
>
> h3. Rename logic optimization:
> * Regardless of whether the rename operation is the source directory and the
> target directory, the quota count must be calculated three times. The first
> time, check whether the moved directory exceeds the target directory quota,
> the second time, calculate the mobile directory quota to update the source
> directory quota, and the third time, calculate the mobile directory
> configuration update to the target directory.
> * I think some of the above three quota quota calculations are unnecessary.
> For example, if all parent directories of the source directory and target
> directory are not configured with quota, there is no need to calculate
> quotaCount. Even if both the source directory and the target directory use
> quota, there is no need to calculate the quota three times. The calculation
> logic for the first and third times is the same, and it only needs to be
> calculated once.
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