Date: Fri, 26 Sep 2008 11:52:08 -0400 From: Ben Kelly <bkelly@vadev.org> To: Bartosz Stec <admin@kkip.pl> Cc: Jeremy Chadwick <koitsu@freebsd.org>, freebsd-stable@freebsd.org Subject: Re: vm.kmem_size settings doesn't affect loader? Message-ID: <C0588997-E405-4651-8D4A-205B8163F97A@vadev.org> In-Reply-To: <48DCA0AF.5050000@kkip.pl> References: <48DB6772.1060400@kkip.pl> <20080925130227.GA13497@icarus.home.lan> <48DB9CAA.9060807@kkip.pl> <20080925145154.GA15486@icarus.home.lan> <48DCA0AF.5050000@kkip.pl>
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On Sep 26, 2008, at 4:43 AM, Bartosz Stec wrote:
> Jeremy Chadwick wrote:
>>
>> These are the tuning settings I use:
>>
>> vm.kmem_size="1536M"
>> vm.kmem_size_max="1536M"
>> vfs.zfs.arc_min="16M"
>> vfs.zfs.arc_max="64M"
>>
> Yesterday I've added 512 MB memory to box (sum 1,5GB), and set
> vm.kmem_size and vm.kmem_size to "1024M". With pieces of 1024MB,
> 512MB, 256MB, 256MB available and 3 memory slots it is hard to have
> 2GB RAM ;)
> Until now it survived world cleaning/building/installing/bonnie++
> benchmarkink/fs scrubing and general usage. Memory usage seems
> stable. If unfortunately kmem exhaustion will happen again I will
> experiment with ARC settings.
> IMHO you've explained gently a lot of zfs tuning concerns in this
> thread and they should be added to tuning guide - espacially
> explanation of ARC and prefetch settings. Thanks again!
Did you increase KVA_PAGES in your kernel config as well?
The default of 256 only allows 1GB of kernel memory total. Setting
KVA_PAGES to 384 would probably be good for a kmem_size of 1GB. This
would give leave you with 512MB of space for other things in the
kernel. In your kernel config:
options KVA_PAGES=384
Sorry if you already knew this. I know its in the zfs tuning guide.
I just hadn't seen it mentioned in the thread yet and wanted to make
sure it wasn't missed.
Hope that helps.
- Ben
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