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Date:      Fri, 04 Mar 2011 09:23:05 +0100
From:      =?ISO-8859-1?Q?Micka=EBl_Can=E9vet?= <canevet@embl.fr>
To:        freebsd-fs@freebsd.org
Subject:   kmem_map too small with ZFS and 8.2-RELEASE
Message-ID:  <1299226985.3391.18.camel@pc286.embl.fr>

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Hello,

I know there is a lot of threads about "kmem_map too small" problems on
former versions of FreeBSD with ZFS, but on the wiki
(http://wiki.freebsd.org/ZFSTuningGuide) it is said that "FreeBSD 7.2+
has improved kernel memory allocation strategy and no tuning may be
necessary on systems with more than 2 GB of RAM."

I have a 64bits machine with 16GB of RAM with FreeBSD 8.2-RELEASE and no
tuning:

# sysctl -a | grep -e "vm.kmem_size_max:" -e "vm.kmem_size:" -e
"vfs.zfs.arc_max:"
vm.kmem_size_max: 329853485875
vm.kmem_size: 16624558080
vfs.zfs.arc_max: 15550816256

This morning this server crashed with:

panic: kmem_malloc(1048576): kmem_map too small: 8658309120 total
allocated

At that time I was doing a quite huge "zfs send | zfs recv" to another
server, this is maybe the origin of the memory consumption.

Does anybody knows why the kernel crashed at around 8GB allocated while
vm.kmem_size and vfs.zfs.arc_max are set at around 16GB and
vm.kmem_size_max is set at around 300GB (is it not a little big huge by
the way ?).

Should I increase this values ?

Thanks a lot for your answers.

Micka=C3=ABl

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