Bandwidth Benchmark (rblnBandwidthLatencyTest)¶

rblnBandwidthLatencyTest measures transfer performance between host and NPU, and between NPUs, and reports:

Bandwidth results (GB/s)
Latency results (us)
NPU connectivity (distance matrix) and topology context

Quick Start¶

Default run (recommended)

1	`$ rblnBandwidthLatencyTest`

Environment and topology

1	`$ rblnBandwidthLatencyTest --test_env_info`

Next steps¶

For concrete command+output pairs, see CLI Examples.
For --tc IDs and selection rules, see Test cases.

Key Concepts and Terminology¶

Transfer directions¶

H2D: host -> NPU
D2H: NPU -> host
D2D: NPU -> NPU (peer-to-peer)

Use --only_d2d when you want to focus on NPU-to-NPU transfers only.

Measurement configuration¶

--test_size: payload size (default: 512M).
--iteration_cnt: measurement iterations.
--warmup: run one warmup iteration before measurement.

Target selection¶

Identifiers
- NPU ID: numeric index used by --npu_id_list (for example: 0, 1).
- Device label: runtime label shown in output (for example: rbln0, rbln1).
Selection rules
- --npu_id_list: comma-separated list of NPU IDs (for example: 0,1,2).
- For test cases 3-6, the set of NPUs involved depends on whether --npu_id_list is provided.

Test cases¶

The available test case IDs are printed by --test_list. The ID is the 0-based index of the entry in the list.

Based on the --test_list output shown later on this page:

ID (`--tc`)	`--test_list` entry	Purpose (high level)
`0`	`RBLN_PERF_TEST_ALL`	Run the default benchmark set (combined bandwidth + latency sweep).
`1`	`RBLN_PERF_BANDWIDTH_TEST_ALL`	Bandwidth-only sweep.
`2`	`RBLN_PERF_LATENCY_TEST_ALL`	Latency-only sweep.
`3`	`RBLN_PERF_BANDWIDTH_TEST`	Bandwidth test for a specific pair (or “first device vs others” if `--npu_id_list` is not provided).
`4`	`RBLN_PERF_LATENCY_TEST`	Latency test for a specific pair (or “first device vs others” if `--npu_id_list` is not provided).
`5`	`RBLN_PERF_BIDIR_BANDWIDTH_TEST`	Bandwidth test across devices.
`6`	`RBLN_PERF_PARALLEL_BANDWIDTH_TEST`	Bandwidth test across devices.

You can run a specific test case by specifying its ID with the --tc option.

Note

If your environment prints a different --test_list order, treat the table above as a guide and rely on the --test_list output as the source of truth.

Command Reference¶

General usage¶

$ rblnBandwidthLatencyTest [options]
$ rblnBandwidthLatencyTest --tc <id> [options]

Global options¶

These options are accepted by the base command and the test-case execution path.

Common options

Option	Description
`-h, --help`	Show the help message and exit.
`-t, --timeout <int>`	Set the timeout in seconds.
`-i, --iteration_cnt <int>`	Set the iteration count.
`--warmup`	Run a warmup iteration before measurement.
`--test_size <str>`	Set the data size (e.g., `4K`, `128M`, `1G`). Default: `512M`.
`--npu_id_list <list>`	Provide a comma-separated list of NPU IDs (e.g., `0,1,2`).
`--only_d2d`	Execute only D2D transfers; skip H2D/D2H stages.
`--test_list`	Print the list of available test cases.
`--tc <int>`	Select the test case ID to run (0-based index). Use the index from `--test_list`.
`--test_env_info`	Print system and device information.
`--skip_test_env_info`	Skip printing environment information when running tests.

Advanced options

Option	Description
`-n, --device_name <int>`	Specify the source device name (ID).
`--get_perf <int>`	Enable performance reporting (`1`: average, `2`: per_inference).
`--priority <int>`	Set context priority (`0-2`: min/normal/high, `3`: kernel, `4`: real-time).
`-r, --hdma_read <int>`	Configure the HDMA direction (`0`: write, `1`: read).
`--numa_node <int>`	Force a NUMA node (default: `-1`).
`--data_pattern <int>`	Set the data pattern value.
`-f, --flags <int>`	Set context flags.
`-g <int>`	Set the execution group ID (no long option is provided).

Tip

If you are unsure about an option, start with Quick Start and rely on rblnBandwidthLatencyTest --help for the complete help text.

CLI Examples¶

Baseline (all tests)Test case listSystem & topologyBandwidth (tc 3)Latency (tc 4)

Summary

Output block	What it is
System + device enumeration	CPU and device list (typically includes PCI BDF and NUMA node).
`P2P Connectivity Distance`	NPU-to-NPU connectivity matrix (reported by the tool).
Bandwidth table	Throughput results (GB/s) across `HOST` and `rbln*` device labels.
Latency results	Synchronization latency in microseconds (us).

Command

Command

$ rblnBandwidthLatencyTest

Output (excerpt)

Default run (excerpt)

CPU : AMD EPYC 9254 24-Core Processor, Vendor ID : AuthenticAMD
Device :
0000:00:01.1/01:00.0 PCI bridge: Broadcom / LSI PEX890xx PCIe Gen 5 Switch (rev b0)
    0000:05:00.0 NODE 0, rbln0, RBLN-CA25(rev-03), pciDevID: 0x1250, NUMA: 0, IOMMU: 70
    0000:06:00.0 NODE 1, rbln1, RBLN-CA25(rev-03), pciDevID: 0x1250, NUMA: 0, IOMMU: 71
    ...
P2P Connectivity Distance
rbln0  0  4  4  ...
rbln1  4  0  4  ...

Device Write bandwidth (GB/s)
S \\ D  HOST  rbln0  rbln1 ...
HOST   0.00  50.91  50.72 ...
rbln0 59.56   0.00  59.31 ...

Device P2P sync latency (us)
rbln0 -> rbln1 2.07 (us)

Summary

Prints the list of available performance test cases.

Command

Command

$ rblnBandwidthLatencyTest --test_list

Output (excerpt)

--test_list (example)

List of tests:
RBLN_PERF_TEST_ALL
RBLN_PERF_BANDWIDTH_TEST_ALL
RBLN_PERF_LATENCY_TEST_ALL
RBLN_PERF_BANDWIDTH_TEST
RBLN_PERF_LATENCY_TEST
RBLN_PERF_BIDIR_BANDWIDTH_TEST
RBLN_PERF_PARALLEL_BANDWIDTH_TEST

Summary

Prints CPU information and system topology details (PCI BDF, NUMA node, and PCIe link information).

Command

Command

$ rblnBandwidthLatencyTest --test_env_info

Output (excerpt)

--test_env_info (excerpt)

CPU : AMD EPYC 9254 24-Core Processor, Vendor ID : AuthenticAMD
Device :
0000:00:01.1/01:00.0 PCI bridge: Broadcom / LSI PEX890xx PCIe Gen 5 Switch (rev b0)
    0000:05:00.0 NODE 0, rbln0, RBLN-CA25(rev-03), pciDevID: 0x1250, NUMA: 0, IOMMU: 70
                                   PCIe full bandwidth 64.0 GB/s (MAX: 64.0), PCIe Gen 5 (MAX: 5), 16 lane (MAX: 16)
                                   MaxPayload 512 bytes, MaxReadReq 512 bytes
...
0000:ce:00.0 NODE 30, rbln30, RBLN-CA25(rev-03), pciDevID: 0x1250, NUMA: 1, IOMMU: 136
                                   PCIe full bandwidth 64.0 GB/s (MAX: 64.0), PCIe Gen 5 (MAX: 5), 16 lane (MAX: 16)
                                   MaxPayload 512 bytes, MaxReadReq 512 bytes
0000:cf:00.0 NODE 31, rbln31, RBLN-CA25(rev-03), pciDevID: 0x1250, NUMA: 1, IOMMU: 137
                                   PCIe full bandwidth 64.0 GB/s (MAX: 64.0), PCIe Gen 5 (MAX: 5), 16 lane (MAX: 16)
                                   MaxPayload 512 bytes, MaxReadReq 512 bytes

Summary

Runs a single bandwidth test case (RBLN_PERF_BANDWIDTH_TEST) for a specific NPU pair.

Command

Command

$ rblnBandwidthLatencyTest --tc 3 --npu_id_list 0,1 --iteration_cnt 1 --test_size 1M --skip_test_env_info

Output (excerpt)

tc 3 (excerpt)

This test will run with size (0x100000)
==============================================================================
[      Run ] : RBLN_PERF_BANDWIDTH_TEST
==============================================================================

[Measure Iteration cnt : 1]
[Measure Buffer Size : 0x100000]

P2P Connectivity Distance
rbln0       0   4   4   4   8   ...
rbln1       4   0   4   4   8   ...

---------------------------------
Device bandwidth (GB/s) *Write
---------------------------------
[H2D] HOST -> rbln0 : MAX 14.71, MIN 14.71, AVG 14.71
[D2D] rbln0 -> rbln1 : MAX 10.29, MIN 10.29, AVG 10.29
[D2H] rbln1 -> HOST : MAX 19.41, MIN 19.41, AVG 19.41

==============================================================================
[     PASS ] : RBLN_PERF_BANDWIDTH_TEST
==============================================================================

Summary

Runs a single latency test case (RBLN_PERF_LATENCY_TEST) for a specific NPU pair.

Command

Command

$ rblnBandwidthLatencyTest --tc 4 --npu_id_list 0,1 --skip_test_env_info

Output (excerpt)

tc 4 (excerpt)

==============================================================================
[      Run ] : RBLN_PERF_LATENCY_TEST
==============================================================================

[Measure Iteration cnt : 1]
[Measure Buffer Size : 0x20000000]

P2P Connectivity Distance
rbln0       0   4   4   4   8   ...
rbln1       4   0   4   4   8   ...

---------------------------------
Device P2P sync latency (us)
---------------------------------
rbln0 -> rbln1 2.07 (us)

==============================================================================
[     PASS ] : RBLN_PERF_LATENCY_TEST
==============================================================================

Troubleshooting¶

The command times out¶

Increase --timeout.
Reduce --test_size or --iteration_cnt to shorten the test.
Run --test_env_info first to confirm devices are detected and topology is printed.

Results fluctuate a lot¶

Use --warmup.
Increase --iteration_cnt and compare averages.
Keep the system load stable (pin workloads, avoid background jobs during benchmarking).

I only want device-to-device numbers¶

Use --only_d2d to skip H2D/D2H stages and focus on NPU-to-NPU transfers.

Bandwidth Benchmark (rblnBandwidthLatencyTest)¶

Quick Start¶

Next steps¶

Key Concepts and Terminology¶

Transfer directions¶

Measurement configuration¶

Target selection¶

Test cases¶

Command Reference¶

General usage¶

Global options¶

CLI Examples¶

Troubleshooting¶

The command times out¶

Results fluctuate a lot¶

I only want device-to-device numbers¶

See also¶