Changes

=== Chunked ghost files ===

=== Chunked ghost files ===

When CRIU checkpoints an invisible (ghost) file with size larger than 12MB, it would try to reduce the size of the corresponding image by seeking for holes (e.g., in sparse files). This approach allow CRIU to save the content of the file into a set of chunks and skip over the "empty" space in a file.

When CRIU checkpoints an invisible (ghost) file with size larger than 12MB, it would try to reduce the size of the corresponding image by seeking for holes (e.g., in sparse files). This approach allows CRIU to save the content of the file into a set of chunks and skip over the "empty" space in a file by keeping track of the offsets.

 

However, determining the offsets in highly sparse file might encounter a significant amount of expensive system calls. In order to reduce the overhead of dumping such ghost files, CRIU supports the <code>--ghost-fiemap</code> option that uses an optimized algorithm based on the fiemap ioctl.

=== Virtual filesystems ===

=== Virtual filesystems ===