Creating thumbnail cache of multiple folders in one go

[Crysler]

I have a photos-folder with a lot of subfolders.
Now I'd like to create the thumbnail cache without the need of clicking on each folder and waiting until the creation process for that folder is finished.

What I did: while being on the main photo folder I activated the option "View > Show files in subfolders".

That did the trick when I tested with a small and a medium set of folders but in the bigger folder (about 650 subfolders with ~50000 files, 400 GB) XnView crashed after a while (without an error message). When I checked, XnView didn't create any cache files.
I had a cache of all of these files earlier (which were gone after a hardware change) which proves that XnView can handle these big data but apparently not the creation in one go.

Is this a bug? Or can I do anything to make XnView handle this case?

[xnview]

you need to use 'options>Thumbnails>Cache - Add folder'

[Crysler]

Ah, I didn't expect this feature to take subdirectories into account.
Worked like a charm, thank you!