Re: kern/57558: pgdaemon 100% busy - no scanning (ZFS case)

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR kern/57558; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/57558: pgdaemon 100% busy - no scanning (ZFS case)
Date: Sun, 5 May 2024 06:45:29 -0000 (UTC)

 kardel%netbsd.org@localhost (Frank Kardel) writes:
 
 >It is not related to XEN at all. Just ZFS + large memory is sufficient 
 >for the problems to occur.
 >Base issue is the big difference between 10% free KVA memory limit and 
 >uvmexp.freetarg.
 
 
 I've added some sysctls that FreeBSD supports and also changed
 how some defaults are computed.
 
 % vmstat -s | grep target
     10922 target free pages
 
 % sysctl vfs.zfs_arc
 vfs.zfs_arc.meta_limit = 0
 vfs.zfs_arc.meta_min = 0
 vfs.zfs_arc.shrink_shift = 0
 vfs.zfs_arc.max = 128770969600
 vfs.zfs_arc.min = 16096371200
 vfs.zfs_arc.compressed = 1
 vfs.zfs_arc.free_target = 10922         <----------
 
 
 I just have no reliable test case to verify that it changes
 the behaviour.
 
 I have uploaded my current patch (still with some debug printfs).
 
 http://cdn.netbsd.org/pub/NetBSD/misc/mlelstv/zfs.diff