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Date:      Mon, 10 May 2010 19:09:41 +0100
From:      Bruce Cran <bruce@cran.org.uk>
To:        freebsd-fs@freebsd.org
Subject:   vm.kmem_size and ZFS on 9-CURRENT
Message-ID:  <201005101909.41614.bruce@cran.org.uk>

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Hi,

I recently converted my /home and /usr slices over to 
ZFS on my desktop running 9-CURRENT amd64 with 6GB RAM. In the process of 
copying data off /var to convert it too, I got the "kmem_map too small" panic, 
which led me to the thread at http://lists.freebsd.org/pipermail/freebsd-
current/2010-April/016984.html which appears to conclude that the defaults 
even on -CURRENT aren't suitable and that vm.kmem_size needs tuned to be 
2xRAM.

Since I had followed the guide at http://wiki.freebsd.org/ZFSQuickStartGuide 
and http://wiki.freebsd.org/ZFSTuningGuide which didn't mention any tuning for 
amd64 with plenty of memory I had thought 9-CURRENT should "just work".   Is 
the tuning of vm.kmem_size really needed?  I've seen mention of an ARC tunable 
too - does it need changed?

-- 
Bruce Cran



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