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Date: Fri, 30 Oct 2020 23:46:22 +0300
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: Cy Schubert <Cy.Schubert@cschubert.com>
Cc: qroxana <qroxana@mail.ru>, freebsd-current@freebsd.org
Subject: Re: OpenZFS: kldload zfs.ko freezes on i386 4GB memory
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On Thu, Oct 29, 2020 at 08:13:00PM -0700, Cy Schubert wrote:

> In message <E1kWvLj-0000GY-Ic.qroxana-mail-ru@smtp29.i.mail.ru>, qroxana 
> writes
> :
> > 
> > Hi,
> >
> > I have an old i386 machine running r364479. After upgrading to
> > r367045, running kldload zfs.ko freezes the whole system.
> >
> > I also tried to replace the 4GB memory with another 2GB one
> > and kldload zfs.ko works without freezing the machine.
> 
> ZFS ARC stresses memory. I've found a number of bad RAM chips over the 
> years using ZFS.
> 
> The OpenZFS upgrade significantly changed how it manages ARC. It's likely 
> that prior to the OpenZFS upgrade your memory wasn't stressed to the point 
> of failure. You can try to mask the problem by reducing your RAM clock rate 
> or or increase one of the other latency settings in your BIOS. However, 
> again, this only masks an already weak RAM chip.

Sounds like performance drop and regression