[
https://issues.apache.org/jira/browse/HDFS-16949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17700822#comment-17700822
]
ASF GitHub Bot commented on HDFS-16949:
---------------------------------------
mkuchenbecker commented on code in PR #5479:
URL: https://github.com/apache/hadoop/pull/5479#discussion_r1137608854
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeMetrics.java:
##########
@@ -323,10 +323,10 @@ public void addIncrementalBlockReport(long latency,
}
}
- public void addReadTransferRate(long readTransferRate) {
- this.readTransferRate.add(readTransferRate);
- for (MutableQuantiles q : readTransferRateQuantiles) {
- q.add(readTransferRate);
+ public void addReadLatencyPerGB(long readLatencyPerGB) {
+ this.readLatencyPerGB.add(readLatencyPerGB);
+ for (MutableQuantiles q : readLatencyPerGBQuantiles) {
Review Comment:
Why don't we modify these quantiles rather than the metric?
I think we have the metric we want, but we want the `lowest` vs `highest`
percentile (ts clear the current percentile is lower=better).
> Update ReadTransferRate to ReadLatencyPerGB for effective percentile metrics
> ----------------------------------------------------------------------------
>
> Key: HDFS-16949
> URL: https://issues.apache.org/jira/browse/HDFS-16949
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Ravindra Dingankar
> Assignee: Ravindra Dingankar
> Priority: Minor
> Labels: pull-request-available
> Fix For: 3.3.0, 3.4.0
>
>
> HDFS-16917 added ReadTransferRate quantiles to calculate the rate which data
> is read per unit of time.
> With percentiles the values are sorted in ascending order and hence for the
> transfer rate p90 gives us the value where 90 percent rates are lower
> (worse), p99 gives us the value where 99 percent values are lower (worse).
> Note that value(p90) < p(99) thus p99 is a better transfer rate as compared
> to p90.
> However as the percentile increases the value should become worse in order to
> know how good our system is.
> Hence instead of calculating the data read transfer rate, we should calculate
> it's inverse. We will instead calculate the time taken for a GB of data to be
> read. ( seconds / GB )
> After this the p90 value will give us 90 percentage of total values where the
> time taken is less than value(p90), similarly for p99 and others.
> Also p(90) < p(99) and here p(99) will become a worse value (taking more time
> each byte) as compared to p(90)
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
