Unexpected not-really-lockups under heavy I/O load

[K900]

Something I'm seeing on my laptop (NixOS, kernel 6.9.7, generally pretty vanilla) is that when there's a big spike in I/O load (in my case usually caused by a NixOS rebuild), the filesystem slows down extremely hard (effectively locks up) for a while, before recovering and continuing as if nothing happened. During the lockup, perf top shows that the CPU time is dominated by

  55,13%  [kernel]                                 [k] osq_lock
  24,07%  [kernel]                                 [k] mutex_spin_on_owner
  17,44%  [kernel]                                 [k] bch2_btree_key_cache_scan

So possibly there's some weird lock contention issue?

[koverstreet]

this is fixed in 6.10

[K900]

Thanks, good to hear! Is it too much effort to backport to 6.9 at this point?

[koverstreet]

this was fixed by the key cache reclaim rewrite