Re: BLAKE3 unstability?

> > > I can reproduce via:
> > > 
> > > $ truncate -s 10G /tmp/test
> > > $ mdconfig -f /tmp/test -S 4096
> > > $ zpool create test /dev/md1
> > > $ zfs create -o checksum=blake3 test/b
> > > $ dd if=/dev/random of=/test/b/noise bs=1M count=4096
> > > $ sync
> > > $ zpool scrub test
> > > $ zpool status
> > 
> > I cannot reproduce this on openzfs/zfs@cb01da68057 (the commit that was
> > most recently merged) built out of tree on either stable/13 70fd40edb86
> > or main 9aa02d5120a.
> > 
> > I'll update a system and see if I can reproduce it with the in-tree ZFS.
> > 
> > - Ryan
> > 
> It did not reproduce for me with in-tree ZFS on main@3c9ad9398fcd either.
> 
> Could you share sysctl kstat.zfs.misc.chksum_bench, maybe we are using
> different implementations?
> I do see that blake3 went in with only a Linux module parameter for the
> implementation selection, so I'll have to fix that. For now we can at least
> see which was fastest, which should be the one selected. You just won't be
> able to manually change it to see if that helps.
> 
> - Ryan

I found the culprit (kernel and base from download.FreeBSD.org
kernel.txz and base.txz respectively) (I forgot about local sysctl.conf...):

kern.sched.steal_thresh=1
kern.sched.preempt_thresh=121

Then

#!/bin/sh

truncate -s 10G /tmp/test
mdconfig -f /tmp/test -S 4096
zpool create test /dev/md0
zfs create -o checksum=blake3 test/b
dd if=/dev/random of=/test/b/noise bs=1M count=4096
sync
zpool scrub test
sleep 3
zpool status

zpool destroy test
mdconfig -d -u 0
rm /tmp/test

As for ULE "tuning", these values give me fine desktop interactivity
when building lang/rust when nice and idprio did not help, so I left
them in sysctl.conf. Not sure if scheduling parameters are worthy of
a ZFS PR, maybe something essential is preempted.