Date: Wed, 13 Jan 2010 19:35:01 +0100 From: Ivan Voras <ivoras@freebsd.org> To: Doug Poland <doug@polands.org> Cc: freebsd-questions@freebsd.org Subject: Re: 8.0-R-p2 ZFS: unixbench causing kmem exhaustion panic Message-ID: <9bbcef731001131035x604cdea1t81b14589cb10ad25@mail.gmail.com> In-Reply-To: <b78f9b16683331ad0f574ecfc1b7f995.squirrel@email.polands.org> References: <8418112cdfada93d83ca0cb5307c1d21.squirrel@email.polands.org> <hil1e8$ebs$1@ger.gmane.org> <b78f9b16683331ad0f574ecfc1b7f995.squirrel@email.polands.org>
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2010/1/13 Doug Poland <doug@polands.org>: > > On Wed, January 13, 2010 11:55, Ivan Voras wrote: >> Doug Poland wrote: >> >>> So the question is, can ZFS be tuned to not panic or hang no matter >>> what I throw at it? >> >> Apparently not. >> >> =C2=A0> I began with a system with no tunables in /boot/loader.conf >> =C2=A0> (vm.kmem_size and vm.kmem_size_max). =C2=A0Then I tried increasi= ng >> =C2=A0> vm.kmem_size and vm.kmem_size_max a GB at a time, until I was at >> 4GB. >> >> Try adding vfs.zfs.arc_max=3D512M to /boot/loader.conf. >> > Would you suggest tweaking the vm.kmem_size tunables in addition to > arc_max? No, unless they auto-tune to something lesser than approximately arc_max*3. I try to set arc_max to be a third (or a quarter) the kmem_size, and tune kmem_size ad_hoc to suit the machine and its purpose. The reason for this is that "arc_max" is just a guideline, not a hard limit... the ZFS ARC usage can and will spike to much larger values, usually in the most inopportune moment.
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