just another sad story in zfs tuning city

[Marco van Tol]

On Sat, Sep 04, 2010 at 09:25:44AM +0900, Randy Bush wrote:
> >> i am tempted to just boot without the zfs memory hacks in loader
> >> conf.  any warnings on doing so?  any other clues also gladly
> >> accepted.
> > 
> > Sticking a wet finger in the air, and assuming /dev/mirror/boota holds a
> > UFS filesystem that's just used to boot from I'd say give kmem_size 1.5x
> > physical, arc_max 1.0x physical, and arc_min 0.5x physical memory to
> > have it compete with the UFS page cache.  After that applications that
> > run can't use more then (0.5x physical memory plus swap space).
> 
> thanks.  it ain't crashed yet.  running some large builds to see how it
> performs.
> 
> but what about just taking the defaults, no parms?  one would hope that
> this would be successful, as that is the simple path.

The defaults go well under what I wrote, and I'm pretty sure for good
reasons.  I _think_ that has to do with that the defaults have to be
prepared for lots more situations then those we setup and tune the
values for.  And ofcourse the arc goes into wired memory as opposed to
page cache in active/inactive under UFS.

I'm not an expert enough to go into lots more detail, but I think what I
write is accurate. :)

Marco

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