vm.kmem_size and ZFS on 9-CURRENT

[Bruce Cran]

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