kern/56887: certain file reads on ZFS file system spend excessive time in pgdaemon, rendering system unusable

[nia%pkgsrc.org@localhost]

>Number:         56887
>Category:       kern
>Synopsis:       certain file reads on ZFS file system spend excessive time in pgdaemon, rendering system unusable
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 15 13:35:00 +0000 2022
>Originator:     nia
>Release:        9.99.97, amd64
>Organization:
TNF
>Environment:
9.99.97, amd64
>Description:
1. install file system with zfs on cgd
2. use it for a year or so
3. occasionally scrub, all error repaired
4. read performance heavily degrades on specific files to the point of unusability, dragging applications to a standstill as all system time is consumed by pgdaemon
5. smartctl finds no serious problems, couple of hundred bad blocks though

>How-To-Repeat:

>Fix:
i have used FreeBSD to rescue its contents and
replaced the file system with FFS