# fun with upgrading: sysctl: unknown oid 'vm.pageout_wakeup_thresh'



## PMc (Dec 6, 2020)

This sysctl knob seems to have disappeared between 11.4 and 12.2. I did not find any notion in release notes about where it may have gone or what the rationale might be.
The only thing certain is, that this knob is required to adjust ZFS cache behaviour in memory-constrained environments. Accordingly, system behaviour is quite shitty now. 

It seems, one is expected to work oneself thru the repo changelogs to figure what to do here...


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## grahamperrin@ (Apr 5, 2021)

https://cgit.freebsd.org/src/log/?qt=grep&q=vm.pageout_wakeup_thresh no clue there, unfortunately. Three commits, none was recent. 

https://github.com/freebsd/freebsd-src/search?q=vm.pageout_wakeup_thresh&type=commits four commits but again, nothing recent.


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## PMc (Apr 5, 2021)

Yeah, thank You - at some point I did find it. It is now inside of a vmd (NUMA domain)

```
./vm/vm_pagequeue.h:    u_int vmd_pageout_wakeup_thresh;/* (c) min pages to wake pagedaemon */
```
and initialization is hardcoded and no longer tuneable:

```
./vm/vm_pageout.c:      vmd->vmd_pageout_wakeup_thresh = (vmd->vmd_free_target / 10) * 9;
```


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