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https://issues.apache.org/jira/browse/HDFS-16949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17707058#comment-17707058
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ASF GitHub Bot commented on HDFS-16949:
---------------------------------------
rdingankar commented on code in PR #5495:
URL: https://github.com/apache/hadoop/pull/5495#discussion_r1153852005
##########
hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/util/TestSampleQuantiles.java:
##########
@@ -92,22 +94,21 @@ public void testClear() throws IOException {
@Test
public void testQuantileError() throws IOException {
final int count = 100000;
- Random r = new Random(0xDEADDEAD);
int[] values = new int[count];
for (int i = 0; i < count; i++) {
values[i] = i + 1;
}
- // Do 10 shuffle/insert/check cycles
- for (int i = 0; i < 10; i++) {
+ // Repeat shuffle/insert/check cycles 10 times
+ for (int i = 0; i < NUM_REPEATS; i++) {
// Shuffle
- Collections.shuffle(Arrays.asList(values), r);
+ Collections.shuffle(Arrays.asList(values), rnd);
Review Comment:
fixed the empty space after comment on L105
> 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)
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