Missing Latency Results

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Last seen: 3 weeks 18 hours ago
Joined: 02/15/2019
Posts: 26
Missing Latency Results

Hello,

Introduction

I've been running performance tests with 1 publisher and 1 subscriber with the following commands:

Publisher:

start cmd /k perftest_java.bat -pub -instances 10 -keyed -dataLen 40980 -domain 2 -latencyCount 1000 -numIter 1000000 -bestEffort -sendQueueSize 1
 
Subscriber:
 
start cmd /k perftest_java.bat -sub -instances 10 -keyed -dataLen 40960 -domain 2 -bestEffort

Error/Issue:

 
When running these tests I write the test results to a .csv file after the test has completed and this feature has worked for previous types of tests. However, within this test these are the recorded latencies of 3 runs of the same test:
 
One-Way Latency (us): 
2931 
1004 
2479 
0 
0 
0 
0 
0 
0 
One-Way Latency (us): 
2735
0
0
0
0
0
0
 
 
One-Way Latency (us): 
3198
2680
2606
0
0
0
0
0
0
0

Question:

 
It would be great to understand what is happening here? Are my test scripts right? If so, why are the results interestingly missing?
 
Thank you
Blitz3r
jmorales's picture
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Last seen: 2 weeks 3 days ago
Joined: 08/28/2013
Posts: 36

Hello,

- I think the first question would be understanding if the output is correclty obtained. If you run perftest with no scripts, what is the output you obtain? I mean, the printed output, is that correct?

- How many latency samples are you getting in the test? What is the throughput in samples per second?

- Why are you measuring latency in a throughput test scenario? Are you aware you are sending at the maximum throughput and that queues are going to be full, so you are obtaining the worse case scenario Latency?

- Why are you setting the sendQueue to 1? Is that experimentally better for your tests? It might be that it is slowing down your system.

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Last seen: 3 weeks 18 hours ago
Joined: 02/15/2019
Posts: 26

Hi Javier,

Thank you for your reply.

Question: If you run PerfTest with not scripts, what is the output you obtain?

Answer: The output is the same. However, where there are 0 values, the output is not shown on the command line. Here is a screenshot:

 

Question: How many latency samples are you getting in the test?

Answer: 1000

Question: What is the throughput in samples per second?

Answer: Averages: Run 1 = 0.9mbps, Run 2 = 2.7mbps, Run 3 = 2.9mbps

Question: Why are you measuring latency in a throughput test scenario?

Answer: I want to find the worst case latency when there is a load on the network.

Question: Why are you setting the send queue size to 1? Is that experimentally better for your tests?

How does it slow down the system? Initially, I thought that it should increase the load to ensure continuous traffic on the network so that the latency at higher throughput is measured.

 

Thanks,

Blitz3r

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Last seen: 1 month 19 hours ago
Joined: 10/23/2019
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Very nicely explained about Missing Latency Results. I hope this post will read maximum peoples.

William Riley, Junior business assignment writer in UK’s leading company.