Inside the struct __wt_background_compact, we have the following fields:

    uint64_t max_file_idle_time;       /* File compact idle time */
    uint64_t max_file_skip_time;       /* File compact skip time */

Their description are not meaningful and one cannot know how they are used without digging into the code. They should be more descriptive:

• We use the first one as a threshold in seconds before we remove the file from the background compaction list. A file is idle if it's not reassessed by the thread. This usually happens when the file is deleted.
• The second one is in seconds, too. This is the time we wait before reassessing a collection that could not be compacted during the previous run so we don't try over and over on something that does not give good compaction results.