[johnnym]

Unfortunately the two commits selected and tried (3b3dd72256d and 805206b941e) didn't limit the search room to a big degree but could rather be used as new good and bad commits.

But when quickly scanning through the remaining commits I recognized a specific one (ae6cd46) that "benefits most mips64 platforms":

Code:

commit ae6cd4623ffb7b807b08788d8e53f7a9259c0c82
Author: miod <miod@openbsd.org>
Date:   Sun Aug 7 19:40:48 2022 +0000

    Use PMAP_PREFER_ALIGN() == 0 rather than !defined(PMAP_PREFER) to enable the
    fast path in the pager code; this benefits most mips64 platforms.
   
    ok kettenis@ mpi@
   
    (cherry picked from commit d600f90f1a804e442018f93ce8ec61f99cd5fb69)

I checked its parent which was still good and then checked it itself which resulted in a bad kernel producing the errors I described here earlier and also on GitHub for IP28. The corresponding issue on GitHub was updated accordingly and has the details.

---

On the way I also could cut down the time needed for compiling considerably by using git diff to create a patch and apply that one to move between revisions and let make find out what to recompile. Not sure if this will also be faster for commits that are further away than what I was operating on.