By the time Linus Torvalds released 5.9-rc1
and closed the merge window for this cycle, 12,866 non-merge changesets had
been pulled into the mainline repository. Nearly 9,000 of those came in
after the first 5.9 merge-window summary
was written. Clearly the kernel-development community remains busy. Much
of what was merged takes the form of cleanups and restructuring, as always,
but there was also a substantial set of new features.

Source: LWN.net – [$] 5.9 Merge window, part 2