Utilizing all NVDEC engines on a single GPU with multiple pipelines

Describe the question.

When running some video decoding benchmarks by building a DALIGenericIterator with a single pipeline on my GH200 system and checking the NVDEC engine utilization via

nvidia-smi dmon -s u

I find my DEC utilization to be capped at ~14%, which would align with only one (out of seven) NVDEC engines being used. According to the documentation I found, the NVIDIA driver should take care of load balancing between the different decoding units.

However, when creating multiple DALI piplines (e.g., seven), I find my DEC utilization to be close to 100%, indicating that all NVDEC engines are used. In raw decoding performance, running multiple pipelines on the same GPU also give me a performance boost.

My questions are:

• Can a single DALI pipeline only use a single decoding unit?
• Is running multiple pipelines on the same GPU the default way to utilize all decoding units?

Check for duplicates

• I have searched the open bugs/issues and have found no duplicates for this bug report