Re: OpenZFS: kldload zfs.ko freezes on i386 4GB memory

On Fri, Oct 30, 2020 at 03:34:10PM -0700, Cy Schubert wrote:

> In message <20201030220809.GG2033_at_zxy.spb.ru>, Slawa Olhovchenkov writes:
> > On Fri, Oct 30, 2020 at 01:53:10PM -0700, Cy Schubert wrote:
> >
> > > In message <20201030204622.GF2033_at_zxy.spb.ru>, Slawa Olhovchenkov writes:
> > > > On Thu, Oct 29, 2020 at 08:13:00PM -0700, Cy Schubert wrote:
> > > >
> > > > > In message <E1kWvLj-0000GY-Ic.qroxana-mail-ru_at_smtp29.i.mail.ru>, qroxan
> > a 
> > > > > 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 like
> > ly 
> > > > > that prior to the OpenZFS upgrade your memory wasn't stressed to the po
> > int 
> > > > > 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
> > > 
> > > How so. Please explain.
> >
> > More stresses memory usually refers to performance penalty.
> > Usually way for better performance is reduce memory access.
> 
> The reason filesystems (UFS, ZFS, EXT4, etc.) cache is to avoid disk 
> accesses. Nanoseconds vs milliseconds.

I mean compared ZoL ZFS ARC vs old (BSD/Opensolaris/Illumos) ZFS ARC.
Any reaason to rise ARC hit rate in ZoL case?