Re: misc/60958 ((Probaby) avoidable stability problems due to default memory management behavior on systems with a lot of RAM, ZFS, and no swap)

[riastradh%NetBSD.org@localhost]

Synopsis: (Probaby) avoidable stability problems due to default memory management behavior on systems with a lot of RAM, ZFS, and no swap

State-Changed-From-To: open->feedback
State-Changed-By: riastradh%NetBSD.org@localhost
State-Changed-When: Tue, 03 Nov 2026 17:49:14 +0000
State-Changed-Why:
There's a lot of speculation and analysis here, and not a lot of
specific evidence.  Can you share some more details like:

1. exactly what observations led you to say `When memory runs out for
   the first and second time [...] ZFS evicts a lot of cache'?

2. exactly what observations led you to say `ZFS will evict so much of
   its own memory that it seems to start to break down'?

3. output of top(1) at various stages?

4. output of the following commands at various stages?
   - echo ps | crash
   - echo ps/w | crash
   - echo show all locks | crash
   - echo show all tstiles | crash

5. if you kill firefox, do the symptoms continue?

6. if you can't start crash, try switching to the first virtual
   terminal ttyE0 with C-A-F1, drop into ddb with C-A-ESC, and take a
   photo of the first page of output of the same commands (ps, ps/w,
   show all locks, show all tstiles) -- don't go wild recording
   everything, mostly just want to see a few wchans to find what
   processes are waiting on

7. if you drop into ddb and type `call wakeup(uvmexp+0x10)' and then
   `continue', do the symptoms continue?

(For context: I have been running zfs (on cgd) and firefox with
hundreds of tabs on laptops with 32-64GB of RAM for years, and have not
encountered these symptoms.)