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Date: Sun, 23 Sep 2007 15:35:46 -0700
From: Darren Reed <darrenr@freebsd.org>
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To: Larry Rosenman <ler@lerctr.org>
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Cc: freebsd-current@freebsd.org, Claus Guttesen <kometen@gmail.com>
Subject: Re: panic: kmem_malloc(131072): kmem_map too small (AMD64)
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Larry Rosenman wrote:
> On Sun, 23 Sep 2007, Claus Guttesen wrote:
>
>>> So I just received this courtesy of ZFS:
>>> panic: kmem_malloc(131072): kmem_map too small: 343027712 total 
>>> allocated
>>> cpuid = 0
>>> KDB: enter: panic
>>>
>>> This was with these settings in loader.conf:
>>> vm.kmem_size=419430400
>>> vm.kmem_size_max=419430400
>>> vfs.zfs.arc_max=409715200
>>
>> How much ram do you have? Is this amd64 or i386?
>
> In my case, 4Gig ram, amd64, and I've seen the panic even with
> 750M vm.kmem_size.
>
> Do we have guidelines on what vm.kmem_size(|_max) should be set to?

My advice would be to tune the ZFS ARC to be smaller than kmem_size.
The above represents a mistake in sizing the ARC.
When using ZFS, I'd tune vm.kmem_size to be as much as 80% of RAM,
unless you're running *large* applications in user space.

Darren