Parallelism for submodule update

Hello, we are using git since many years with also heavily using submodules.

When updating the submodules, only the fetching part is done in parallel (with config submodule.fetchjobs or --jobs) but the checkout is done sequentially

What I’ve recognized when cloning with
- scalar clone --full-clone --recurse-submodules <URL>
or
- git clone --filter=blob:none --also-filter-submodules --recurse-submodules <URL>

We loose performance, as the fetch of the blobs is done in the sequential checkout part, instead of in the parallel part.

Furthermore, the utilization - without partial clone - of network and harddisk is not always good, as first the network is utilized (fetch) and then the harddisk (checkout)

As the checkout part is local to the submodule (no shared resources to block), it would be great if we could move the checkout into the parallelized part. E.g. by doing fetch and checkout (with blob fetching) in one step with e.g. run_processes_parallel_tr2

I expect that this significantly improves the performance, especially when using partial clones.

Do you think this is possible? Do I miss anything in my thoughts?

Best regards,

Christian Zitzmann