[OSPP 2024] optimize image by prefetch analysis

[imeoer]

We can statically analyze the image entrypoint dependency, or use runtime dynamic analysis technologies such as ebpf, fanotify, metric, etc. to obtain the container file access pattern, and then build this part of data into an independent image layer:

• preferentially fetch blob during the image startup phase to reduce network and disk IO.
• avoid frequent image builds, allows for better local cache utilization.

Possible implementation steps:

• follow the doc to get an accessed files list for a OCI / nydus image.
• implement cat accessed-files.txt | nydusify optimize --policy separated-prefetch-blob --target $existed-nydus-image --output $new-nydus-image to generate a new image, which references a new blob included prefetch file chunks.