Performing latency tests for platform verification - Low latency tuning | Scalability and performance

Prerequisites for running latency tests
Measuring latency
Running the latency tests
Generating a latency test failure report
Generating a JUnit latency test report
Running latency tests on a single-node OpenShift cluster
Running latency tests in a disconnected cluster
Troubleshooting errors with the cnf-tests container

You can use the Cloud-native Network Functions (CNF) tests image to run latency tests on a CNF-enabled OpenShift Container Platform cluster, where all the components required for running CNF workloads are installed. Run the latency tests to validate node tuning for your workload.

The cnf-tests container image is available at registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15.

Prerequisites for running latency tests

Your cluster must meet the following requirements before you can run the latency tests:

You have configured a performance profile with the Node Tuning Operator.
You have applied all the required CNF configurations in the cluster.
You have a pre-existing MachineConfigPool CR applied in the cluster. The default worker pool is worker-cnf.

Additional resources

Scheduling a workload onto a worker with real-time capabilities

Measuring latency

The cnf-tests image uses three tools to measure the latency of the system:

hwlatdetect
cyclictest
oslat

Each tool has a specific use. Use the tools in sequence to achieve reliable test results.

hwlatdetect: Measures the baseline that the bare-metal hardware can achieve. Before proceeding with the next latency test, ensure that the latency reported by hwlatdetect meets the required threshold because you cannot fix hardware latency spikes by operating system tuning.
cyclictest: Verifies the real-time kernel scheduler latency after hwlatdetect passes validation. The cyclictest tool schedules a repeated timer and measures the difference between the desired and the actual trigger times. The difference can uncover basic issues with the tuning caused by interrupts or process priorities. The tool must run on a real-time kernel.
oslat: Behaves similarly to a CPU-intensive DPDK application and measures all the interruptions and disruptions to the busy loop that simulates CPU heavy data processing.

The tests introduce the following environment variables:

Environment variables Description

LATENCY_TEST_DELAY

Specifies the amount of time in seconds after which the test starts running. You can use the variable to allow the CPU manager reconcile loop to update the default CPU pool. The default value is 0.

LATENCY_TEST_CPUS

Specifies the number of CPUs that the pod running the latency tests uses. If you do not set the variable, the default configuration includes all isolated CPUs.

LATENCY_TEST_RUNTIME

Specifies the amount of time in seconds that the latency test must run. The default value is 300 seconds.

To prevent the Ginkgo 2.0 test suite from timing out before the latency tests complete, set the -ginkgo.timeout flag to a value greater than LATENCY_TEST_RUNTIME + 2 minutes. If you also set a LATENCY_TEST_DELAY value then you must set -ginkgo.timeout to a value greater than LATENCY_TEST_RUNTIME + LATENCY_TEST_DELAY + 2 minutes. The default timeout value for the Ginkgo 2.0 test suite is 1 hour.

HWLATDETECT_MAXIMUM_LATENCY

Specifies the maximum acceptable hardware latency in microseconds for the workload and operating system. If you do not set the value of HWLATDETECT_MAXIMUM_LATENCY or MAXIMUM_LATENCY, the tool compares the default expected threshold (20μs) and the actual maximum latency in the tool itself. Then, the test fails or succeeds accordingly.

CYCLICTEST_MAXIMUM_LATENCY

Specifies the maximum latency in microseconds that all threads expect before waking up during the cyclictest run. If you do not set the value of CYCLICTEST_MAXIMUM_LATENCY or MAXIMUM_LATENCY, the tool skips the comparison of the expected and the actual maximum latency.

OSLAT_MAXIMUM_LATENCY

Specifies the maximum acceptable latency in microseconds for the oslat test results. If you do not set the value of OSLAT_MAXIMUM_LATENCY or MAXIMUM_LATENCY, the tool skips the comparison of the expected and the actual maximum latency.

MAXIMUM_LATENCY

Unified variable that specifies the maximum acceptable latency in microseconds. Applicable for all available latency tools.

Variables that are specific to a latency tool take precedence over unified variables. For example, if OSLAT_MAXIMUM_LATENCY is set to 30 microseconds and MAXIMUM_LATENCY is set to 10 microseconds, the oslat test will run with maximum acceptable latency of 30 microseconds.

Running the latency tests

Run the cluster latency tests to validate node tuning for your Cloud-native Network Functions (CNF) workload.

When executing podman commands as a non-root or non-privileged user, mounting paths can fail with permission denied errors. To make the podman command work, append :Z to the volumes creation; for example, -v $(pwd)/:/kubeconfig:Z. This allows podman to do the proper SELinux relabeling.

Procedure

Open a shell prompt in the directory containing the kubeconfig file.

You provide the test image with a kubeconfig file in current directory and its related $KUBECONFIG environment variable, mounted through a volume. This allows the running container to use the kubeconfig file from inside the container.

Run the latency tests by entering the following command:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e LATENCY_TEST_RUNTIME=<time_in_seconds>\
-e MAXIMUM_LATENCY=<time_in_microseconds> \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 /usr/bin/test-run.sh \
--ginkgo.v --ginkgo.timeout="24h"

Optional: Append --ginkgo.dryRun flag to run the latency tests in dry-run mode. This is useful for checking what commands the tests run.
Optional: Append --ginkgo.v flag to run the tests with increased verbosity.
Optional: Append --ginkgo.timeout="24h" flag to ensure the Ginkgo 2.0 test suite does not timeout before the latency tests complete.

The default runtime for each test is 300 seconds. For valid latency test results, run the tests for at least 12 hours by updating the LATENCY_TEST_RUNTIME variable.

Running hwlatdetect

The hwlatdetect tool is available in the rt-kernel package with a regular subscription of Red Hat Enterprise Linux (RHEL) 9.x.

Prerequisites

You have installed the real-time kernel in the cluster.
You have logged in to registry.redhat.io with your Customer Portal credentials.

Procedure

To run the hwlatdetect tests, run the following command, substituting variable values as appropriate:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e LATENCY_TEST_RUNTIME=600 -e MAXIMUM_LATENCY=20 \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
/usr/bin/test-run.sh --ginkgo.focus="hwlatdetect" --ginkgo.v --ginkgo.timeout="24h"

The hwlatdetect test runs for 10 minutes (600 seconds). The test runs successfully when the maximum observed latency is lower than MAXIMUM_LATENCY (20 μs).

If the results exceed the latency threshold, the test fails.

For valid results, the test should run for at least 12 hours.

Example failure output

running /usr/bin/cnftests -ginkgo.v -ginkgo.focus=hwlatdetect
I0908 15:25:20.023712      27 request.go:601] Waited for 1.046586367s due to client-side throttling, not priority and fairness, request: GET:https://api.hlxcl6.lab.eng.tlv2.redhat.com:6443/apis/imageregistry.operator.openshift.io/v1?timeout=32s
Running Suite: CNF Features e2e integration tests
=================================================
Random Seed: 1662650718
Will run 1 of 3 specs

[...]

• Failure [283.574 seconds]
[performance] Latency Test
/remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:62
  with the hwlatdetect image
  /remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:228
    should succeed [It]
    /remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:236

    Log file created at: 2022/09/08 15:25:27
    Running on machine: hwlatdetect-b6n4n
    Binary: Built with gc go1.17.12 for linux/amd64
    Log line format: [IWEF]mmdd hh:mm:ss.uuuuuu threadid file:line] msg
    I0908 15:25:27.160620       1 node.go:39] Environment information: /proc/cmdline: BOOT_IMAGE=(hd1,gpt3)/ostree/rhcos-c6491e1eedf6c1f12ef7b95e14ee720bf48359750ac900b7863c625769ef5fb9/vmlinuz-4.18.0-372.19.1.el8_6.x86_64 random.trust_cpu=on console=tty0 console=ttyS0,115200n8 ignition.platform.id=metal ostree=/ostree/boot.1/rhcos/c6491e1eedf6c1f12ef7b95e14ee720bf48359750ac900b7863c625769ef5fb9/0 ip=dhcp root=UUID=5f80c283-f6e6-4a27-9b47-a287157483b2 rw rootflags=prjquota boot=UUID=773bf59a-bafd-48fc-9a87-f62252d739d3 skew_tick=1 nohz=on rcu_nocbs=0-3 tuned.non_isolcpus=0000ffff,ffffffff,fffffff0 systemd.cpu_affinity=4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79 intel_iommu=on iommu=pt isolcpus=managed_irq,0-3 nohz_full=0-3 tsc=nowatchdog nosoftlockup nmi_watchdog=0 mce=off skew_tick=1 rcutree.kthread_prio=11 + +
    I0908 15:25:27.160830       1 node.go:46] Environment information: kernel version 4.18.0-372.19.1.el8_6.x86_64
    I0908 15:25:27.160857       1 main.go:50] running the hwlatdetect command with arguments [/usr/bin/hwlatdetect --threshold 1 --hardlimit 1 --duration 100 --window 10000000us --width 950000us]
    F0908 15:27:10.603523       1 main.go:53] failed to run hwlatdetect command; out: hwlatdetect:  test duration 100 seconds
       detector: tracer
       parameters:
            Latency threshold: 1us (1)
            Sample window:     10000000us
            Sample width:      950000us
         Non-sampling period:  9050000us
            Output File:       None

    Starting test
    test finished
    Max Latency: 326us (2)
    Samples recorded: 5
    Samples exceeding threshold: 5
    ts: 1662650739.017274507, inner:6, outer:6
    ts: 1662650749.257272414, inner:14, outer:326
    ts: 1662650779.977272835, inner:314, outer:12
    ts: 1662650800.457272384, inner:3, outer:9
    ts: 1662650810.697273520, inner:3, outer:2

[...]

JUnit report was created: /junit.xml/cnftests-junit.xml


Summarizing 1 Failure:

[Fail] [performance] Latency Test with the hwlatdetect image [It] should succeed
/remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:476

Ran 1 of 194 Specs in 365.797 seconds
FAIL! -- 0 Passed | 1 Failed | 0 Pending | 2 Skipped
--- FAIL: TestTest (366.08s)
FAIL

1	You can configure the latency threshold by using the `MAXIMUM_LATENCY` or the `HWLATDETECT_MAXIMUM_LATENCY` environment variables.
2	The maximum latency value measured during the test.

Example hwlatdetect test results

You can capture the following types of results:

Rough results that are gathered after each run to create a history of impact on any changes made throughout the test.
The combined set of the rough tests with the best results and configuration settings.

Example of good results

hwlatdetect: test duration 3600 seconds
detector: tracer
parameters:
Latency threshold: 10us
Sample window: 1000000us
Sample width: 950000us
Non-sampling period: 50000us
Output File: None

Starting test
test finished
Max Latency: Below threshold
Samples recorded: 0

The hwlatdetect tool only provides output if the sample exceeds the specified threshold.

Example of bad results

hwlatdetect: test duration 3600 seconds
detector: tracer
parameters:Latency threshold: 10usSample window: 1000000us
Sample width: 950000usNon-sampling period: 50000usOutput File: None

Starting tests:1610542421.275784439, inner:78, outer:81
ts: 1610542444.330561619, inner:27, outer:28
ts: 1610542445.332549975, inner:39, outer:38
ts: 1610542541.568546097, inner:47, outer:32
ts: 1610542590.681548531, inner:13, outer:17
ts: 1610543033.818801482, inner:29, outer:30
ts: 1610543080.938801990, inner:90, outer:76
ts: 1610543129.065549639, inner:28, outer:39
ts: 1610543474.859552115, inner:28, outer:35
ts: 1610543523.973856571, inner:52, outer:49
ts: 1610543572.089799738, inner:27, outer:30
ts: 1610543573.091550771, inner:34, outer:28
ts: 1610543574.093555202, inner:116, outer:63

The output of hwlatdetect shows that multiple samples exceed the threshold. However, the same output can indicate different results based on the following factors:

The duration of the test
The number of CPU cores
The host firmware settings

Before proceeding with the next latency test, ensure that the latency reported by hwlatdetect meets the required threshold. Fixing latencies introduced by hardware might require you to contact the system vendor support.

Not all latency spikes are hardware related. Ensure that you tune the host firmware to meet your workload requirements. For more information, see Setting firmware parameters for system tuning.

Running cyclictest

The cyclictest tool measures the real-time kernel scheduler latency on the specified CPUs.

Prerequisites

You have logged in to registry.redhat.io with your Customer Portal credentials.
You have installed the real-time kernel in the cluster.
You have applied a cluster performance profile by using Node Tuning Operator.

Procedure

To perform the cyclictest, run the following command, substituting variable values as appropriate:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e LATENCY_TEST_CPUS=10 -e LATENCY_TEST_RUNTIME=600 -e MAXIMUM_LATENCY=20 \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
/usr/bin/test-run.sh --ginkgo.focus="cyclictest" --ginkgo.v --ginkgo.timeout="24h"

The command runs the cyclictest tool for 10 minutes (600 seconds). The test runs successfully when the maximum observed latency is lower than MAXIMUM_LATENCY (in this example, 20 μs). Latency spikes of 20 μs and above are generally not acceptable for telco RAN workloads.

If the results exceed the latency threshold, the test fails.

For valid results, the test should run for at least 12 hours.

Example failure output

running /usr/bin/cnftests -ginkgo.v -ginkgo.focus=cyclictest
I0908 13:01:59.193776      27 request.go:601] Waited for 1.046228824s due to client-side throttling, not priority and fairness, request: GET:https://api.compute-1.example.com:6443/apis/packages.operators.coreos.com/v1?timeout=32s
Running Suite: CNF Features e2e integration tests
=================================================
Random Seed: 1662642118
Will run 1 of 3 specs

[...]

Summarizing 1 Failure:

[Fail] [performance] Latency Test with the cyclictest image [It] should succeed
/remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:220

Ran 1 of 194 Specs in 161.151 seconds
FAIL! -- 0 Passed | 1 Failed | 0 Pending | 2 Skipped
--- FAIL: TestTest (161.48s)
FAIL

Example cyclictest results

The same output can indicate different results for different workloads. For example, spikes up to 18μs are acceptable for 4G DU workloads, but not for 5G DU workloads.

Example of good results

running cmd: cyclictest -q -D 10m -p 1 -t 16 -a 2,4,6,8,10,12,14,16,54,56,58,60,62,64,66,68 -h 30 -i 1000 -m
# Histogram
000000 000000   000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000
000001 000000   000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000
000002 579506   535967  418614  573648  532870  529897  489306  558076  582350  585188  583793  223781  532480  569130  472250  576043
More histogram entries ...
# Total: 000600000 000600000 000600000 000599999 000599999 000599999 000599998 000599998 000599998 000599997 000599997 000599996 000599996 000599995 000599995 000599995
# Min Latencies: 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002
# Avg Latencies: 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002
# Max Latencies: 00005 00005 00004 00005 00004 00004 00005 00005 00006 00005 00004 00005 00004 00004 00005 00004
# Histogram Overflows: 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
# Histogram Overflow at cycle number:
# Thread 0:
# Thread 1:
# Thread 2:
# Thread 3:
# Thread 4:
# Thread 5:
# Thread 6:
# Thread 7:
# Thread 8:
# Thread 9:
# Thread 10:
# Thread 11:
# Thread 12:
# Thread 13:
# Thread 14:
# Thread 15:

Example of bad results

running cmd: cyclictest -q -D 10m -p 1 -t 16 -a 2,4,6,8,10,12,14,16,54,56,58,60,62,64,66,68 -h 30 -i 1000 -m
# Histogram
000000 000000   000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000
000001 000000   000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000  000000
000002 564632   579686  354911  563036  492543  521983  515884  378266  592621  463547  482764  591976  590409  588145  589556  353518
More histogram entries ...
# Total: 000599999 000599999 000599999 000599997 000599997 000599998 000599998 000599997 000599997 000599996 000599995 000599996 000599995 000599995 000599995 000599993
# Min Latencies: 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002
# Avg Latencies: 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002 00002
# Max Latencies: 00493 00387 00271 00619 00541 00513 00009 00389 00252 00215 00539 00498 00363 00204 00068 00520
# Histogram Overflows: 00001 00001 00001 00002 00002 00001 00000 00001 00001 00001 00002 00001 00001 00001 00001 00002
# Histogram Overflow at cycle number:
# Thread 0: 155922
# Thread 1: 110064
# Thread 2: 110064
# Thread 3: 110063 155921
# Thread 4: 110063 155921
# Thread 5: 155920
# Thread 6:
# Thread 7: 110062
# Thread 8: 110062
# Thread 9: 155919
# Thread 10: 110061 155919
# Thread 11: 155918
# Thread 12: 155918
# Thread 13: 110060
# Thread 14: 110060
# Thread 15: 110059 155917

Running oslat

The oslat test simulates a CPU-intensive DPDK application and measures all the interruptions and disruptions to test how the cluster handles CPU heavy data processing.

Prerequisites

You have logged in to registry.redhat.io with your Customer Portal credentials.
You have applied a cluster performance profile by using the Node Tuning Operator.

Procedure

To perform the oslat test, run the following command, substituting variable values as appropriate:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e LATENCY_TEST_CPUS=10 -e LATENCY_TEST_RUNTIME=600 -e MAXIMUM_LATENCY=20 \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
/usr/bin/test-run.sh --ginkgo.focus="oslat" --ginkgo.v --ginkgo.timeout="24h"

LATENCY_TEST_CPUS specifies the number of CPUs to test with the oslat command.

The command runs the oslat tool for 10 minutes (600 seconds). The test runs successfully when the maximum observed latency is lower than MAXIMUM_LATENCY (20 μs).

If the results exceed the latency threshold, the test fails.

For valid results, the test should run for at least 12 hours.

Example failure output

running /usr/bin/cnftests -ginkgo.v -ginkgo.focus=oslat
I0908 12:51:55.999393      27 request.go:601] Waited for 1.044848101s due to client-side throttling, not priority and fairness, request: GET:https://compute-1.example.com:6443/apis/machineconfiguration.openshift.io/v1?timeout=32s
Running Suite: CNF Features e2e integration tests
=================================================
Random Seed: 1662641514
Will run 1 of 3 specs

[...]

• Failure [77.833 seconds]
[performance] Latency Test
/remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:62
  with the oslat image
  /remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:128
    should succeed [It]
    /remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:153

    The current latency 304 is bigger than the expected one 1 : (1)

[...]

Summarizing 1 Failure:

[Fail] [performance] Latency Test with the oslat image [It] should succeed
/remote-source/app/vendor/github.com/openshift/cluster-node-tuning-operator/test/e2e/performanceprofile/functests/4_latency/latency.go:177

Ran 1 of 194 Specs in 161.091 seconds
FAIL! -- 0 Passed | 1 Failed | 0 Pending | 2 Skipped
--- FAIL: TestTest (161.42s)
FAIL

1	In this example, the measured latency is outside the maximum allowed value.

Generating a latency test failure report

Use the following procedures to generate a JUnit latency test output and test failure report.

Prerequisites

You have installed the OpenShift CLI (oc).
You have logged in as a user with cluster-admin privileges.

Procedure

Create a test failure report with information about the cluster state and resources for troubleshooting by passing the --report parameter with the path to where the report is dumped:
```
$ podman run -v $(pwd)/:/kubeconfig:Z -v $(pwd)/reportdest:<report_folder_path> \
-e KUBECONFIG=/kubeconfig/kubeconfig registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
/usr/bin/test-run.sh --report <report_folder_path> --ginkgo.v
```
where:

<report_folder_path>

Is the path to the folder where the report is generated.

Generating a JUnit latency test report

Use the following procedures to generate a JUnit latency test output and test failure report.

Prerequisites

You have installed the OpenShift CLI (oc).
You have logged in as a user with cluster-admin privileges.

Procedure

Create a JUnit-compliant XML report by passing the --junit parameter together with the path to where the report is dumped:

You must create the junit folder before running this command.

$ podman run -v $(pwd)/:/kubeconfig:Z -v $(pwd)/junit:/junit \
-e KUBECONFIG=/kubeconfig/kubeconfig registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
/usr/bin/test-run.sh --ginkgo.junit-report junit/<file-name>.xml --ginkgo.v

where:

junit: Is the folder where the junit report is stored.

Running latency tests on a single-node OpenShift cluster

You can run latency tests on single-node OpenShift clusters.

Prerequisites

You have installed the OpenShift CLI (oc).
You have logged in as a user with cluster-admin privileges.
You have applied a cluster performance profile by using the Node Tuning Operator.

Procedure

To run the latency tests on a single-node OpenShift cluster, run the following command:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e LATENCY_TEST_RUNTIME=<time_in_seconds> registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
/usr/bin/test-run.sh --ginkgo.v --ginkgo.timeout="24h"

The default runtime for each test is 300 seconds. For valid latency test results, run the tests for at least 12 hours by updating the LATENCY_TEST_RUNTIME variable. To run the buckets latency validation step, you must specify a maximum latency. For details on maximum latency variables, see the table in the "Measuring latency" section.

After running the test suite, all the dangling resources are cleaned up.

Running latency tests in a disconnected cluster

The CNF tests image can run tests in a disconnected cluster that is not able to reach external registries. This requires two steps:

Mirroring the cnf-tests image to the custom disconnected registry.
Instructing the tests to consume the images from the custom disconnected registry.

Mirroring the images to a custom registry accessible from the cluster

A mirror executable is shipped in the image to provide the input required by oc to mirror the test image to a local registry.

Run this command from an intermediate machine that has access to the cluster and registry.redhat.io:
```
$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
/usr/bin/mirror -registry <disconnected_registry> | oc image mirror -f -
```
where:

<disconnected_registry>

Is the disconnected mirror registry you have configured, for example, my.local.registry:5000/.

When you have mirrored the cnf-tests image into the disconnected registry, you must override the original registry used to fetch the images when running the tests, for example:

podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e IMAGE_REGISTRY="<disconnected_registry>" \
-e CNF_TESTS_IMAGE="cnf-tests-rhel8:v4.15" \
-e LATENCY_TEST_RUNTIME=<time_in_seconds> \
<disconnected_registry>/cnf-tests-rhel8:v4.15 /usr/bin/test-run.sh --ginkgo.v --ginkgo.timeout="24h"

Configuring the tests to consume images from a custom registry

You can run the latency tests using a custom test image and image registry using CNF_TESTS_IMAGE and IMAGE_REGISTRY variables.

To configure the latency tests to use a custom test image and image registry, run the following command:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e IMAGE_REGISTRY="<custom_image_registry>" \
-e CNF_TESTS_IMAGE="<custom_cnf-tests_image>" \
-e LATENCY_TEST_RUNTIME=<time_in_seconds> \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 /usr/bin/test-run.sh --ginkgo.v --ginkgo.timeout="24h"

where:

<custom_image_registry>: is the custom image registry, for example, custom.registry:5000/.
<custom_cnf-tests_image>: is the custom cnf-tests image, for example, custom-cnf-tests-image:latest.

Mirroring images to the cluster OpenShift image registry

OpenShift Container Platform provides a built-in container image registry, which runs as a standard workload on the cluster.

Procedure

Gain external access to the registry by exposing it with a route:

$ oc patch configs.imageregistry.operator.openshift.io/cluster --patch '{"spec":{"defaultRoute":true}}' --type=merge

Fetch the registry endpoint by running the following command:

$ REGISTRY=$(oc get route default-route -n openshift-image-registry --template='{{ .spec.host }}')

Create a namespace for exposing the images:
```
$ oc create ns cnftests
```

Make the image stream available to all the namespaces used for tests. This is required to allow the tests namespaces to fetch the images from the cnf-tests image stream. Run the following commands:

$ oc policy add-role-to-user system:image-puller system:serviceaccount:cnf-features-testing:default --namespace=cnftests

$ oc policy add-role-to-user system:image-puller system:serviceaccount:performance-addon-operators-testing:default --namespace=cnftests

Retrieve the docker secret name and auth token by running the following commands:

$ SECRET=$(oc -n cnftests get secret | grep builder-docker | awk {'print $1'}

$ TOKEN=$(oc -n cnftests get secret $SECRET -o jsonpath="{.data['\.dockercfg']}" | base64 --decode | jq '.["image-registry.openshift-image-registry.svc:5000"].auth')

Create a dockerauth.json file, for example:

$ echo "{\"auths\": { \"$REGISTRY\": { \"auth\": $TOKEN } }}" > dockerauth.json

Do the image mirroring:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
registry.redhat.io/openshift4/cnf-tests-rhel8:4.15 \
/usr/bin/mirror -registry $REGISTRY/cnftests |  oc image mirror --insecure=true \
-a=$(pwd)/dockerauth.json -f -

Run the tests:

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
-e LATENCY_TEST_RUNTIME=<time_in_seconds> \
-e IMAGE_REGISTRY=image-registry.openshift-image-registry.svc:5000/cnftests cnf-tests-local:latest /usr/bin/test-run.sh --ginkgo.v --ginkgo.timeout="24h"

Mirroring a different set of test images

You can optionally change the default upstream images that are mirrored for the latency tests.

Procedure

The mirror command tries to mirror the upstream images by default. This can be overridden by passing a file with the following format to the image:
```
[
    {
        "registry": "public.registry.io:5000",
        "image": "imageforcnftests:4.15"
    }
]
```

Pass the file to the mirror command, for example saving it locally as images.json. With the following command, the local path is mounted in /kubeconfig inside the container and that can be passed to the mirror command.

$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 /usr/bin/mirror \
--registry "my.local.registry:5000/" --images "/kubeconfig/images.json" \
|  oc image mirror -f -

Troubleshooting errors with the cnf-tests container

To run latency tests, the cluster must be accessible from within the cnf-tests container.

Prerequisites

You have installed the OpenShift CLI (oc).
You have logged in as a user with cluster-admin privileges.

Procedure

Verify that the cluster is accessible from inside the cnf-tests container by running the following command:
```
$ podman run -v $(pwd)/:/kubeconfig:Z -e KUBECONFIG=/kubeconfig/kubeconfig \
registry.redhat.io/openshift4/cnf-tests-rhel8:v4.15 \
oc get nodes
```
If this command does not work, an error related to spanning across DNS, MTU size, or firewall access might be occurring.