Date: Wed, 22 Apr 2009 12:30:20 +0200 From: Gary Jennejohn <gary.jennejohn@freenet.de> To: Kai Gallasch <gallasch@free.de> Cc: freebsd-fs@freebsd.org Subject: Re: FreeBSD 7.2-RC1 - ZFS related kernel panic "kmem_map too small" Message-ID: <20090422123020.42b756c1@ernst.jennejohn.org> In-Reply-To: <49EE49D8.7000902@free.de> References: <49EE49D8.7000902@free.de>
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On Wed, 22 Apr 2009 00:34:00 +0200 Kai Gallasch <gallasch@free.de> wrote: [snip a lot of stuff] > In /usr/src/UPDATING I read: > > [..] > > 20090207: > ZFS users on amd64 machines with 4GB or more of RAM should > reevaluate their need for setting vm.kmem_size_max and > vm.kmem_size manually. In fact, after recent changes to the > kernel, the default value of vm.kmem_size is larger than the > suggested manual setting in most ZFS/FreeBSD tuning guides. > > So I understood this as "vm.kmem_size is set unnecessary large by > default. You should think about decreasing it to save some RAM" > > On my amd64 server the default values of kmem_size are > > vm.kmem_size_scale: 3 > vm.kmem_size_max: 3865468109 > vm.kmem_size_min: 0 > vm.kmem_size: 1201446912 > > Can someone give me a hint how to debug this problem further, or how to > find some reasonable values for setting vm.kmem_size_max and > vm.kmem_size with 16G of RAM? > Hmm, I wonder whether this applies to 7.2-RC1. I don't know whether the kernel changes have been committed to 7.2 or whether they were already present when we started work on 7.2 because I haven't been paying much attention. On my 8-current amd64 machine with only 4GB of RAM I see larger values than you see with 16GB: sysctl vm.kmem_size_max vm.kmem_size_max: 4509713203 sysctl vm.kmem_size vm.kmem_size: 1335824384 --- Gary Jennejohn
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