vm.kmem_size settings doesn't affect loader?

Bartosz Stec admin at kkip.pl
Mon Sep 29 08:13:31 UTC 2008

Ben Kelly wrote:
> 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
Indeed I know that.

    options         KVA_PAGES=512

is included in my kernel config.
Until now:

    # uptime
    10:12  up 3 days, 10:32, 1 user, load averages: 0,00 0,03 0,00

Thanks :)

Bartosz Stec 

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