It seems that when dnf is downloading metadata, it basically does download (repo1) decompress/process (repo1) download/process (repo2) decompress/process (repo2) and so on. Since downloading is not a cpu-heavy task but processing/decompressing of metadata usually is, it would make sense to preform the decompression/processing in the background, without blocking the download of the rest of the repository metadata.
Hello, we'll look into this when time to optimize comes. Most users however use scheduled makecache and wouldn't benefit from this.
*** Bug 1084564 has been marked as a duplicate of this bug. ***
*** This bug has been marked as a duplicate of bug 850896 ***