Date: Sat, 23 Jan 2010 11:54:08 -0500 From: Adam McDougall <mcdouga9@egr.msu.edu> To: Artem Belevich <fbsdlist@src.cx> Cc: freebsd-fs@freebsd.org Subject: Re: Repeatable ZFS "kmem map too small" panic on 8.0-STABLE Message-ID: <20100123165408.GR86054@egr.msu.edu> In-Reply-To: <ed91d4a81001221824u5c222e08l80395398c0a61c16@mail.gmail.com> References: <4B58BD2D.30803@rcn.com> <ed91d4a81001211421r4f7ba7a8n1c92bfc413e5feed@mail.gmail.com> <4B58D4D3.80009@egr.msu.edu> <20100122042843.GA8858@polands.org> <ed91d4a81001212209o3cf5955fw1eb0dd78703ad905@mail.gmail.com> <a8b9c9e35a14c4ada1c8f2602c91db63.squirrel@email.polands.org> <a4ab3938f95de65086a18607309178c4.squirrel@email.polands.org> <ed91d4a81001221211j2bc05b6bv22a51a8b2fcbcec1@mail.gmail.com> <1308c71eec426200d4c34b926bba8806.squirrel@email.polands.org> <ed91d4a81001221824u5c222e08l80395398c0a61c16@mail.gmail.com>
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On Fri, Jan 22, 2010 at 06:24:36PM -0800, Artem Belevich wrote:
> % sysctl hw.physmem vm.kmem_size vm.kmem_size_max vfs.zfs.arc_max
>
> hw.physmem:4102688768
> vm.kmem_size: 2147483648
Here's your problem -- kmem_size is for some reason only 2G.
Argh! I ran into that before. The code in sys/kern/kern_malloc.c
intentionally limits kmem_size to twice the physical memory size:
/*
* Limit kmem virtual size to twice the physical memory.
* This allows for kmem map sparseness, but limits the size
* to something sane. Be careful to not overflow the 32bit
* ints while doing the check.
*/
if (((vm_kmem_size / 2) / PAGE_SIZE) > cnt.v_page_count)
vm_kmem_size = 2 * cnt.v_page_count * PAGE_SIZE;
So, either comment out these lines or just set vm.kmem_size to
slightly below 8G.
--Artem
That works for me and a friend of mine, I didn't realize that my kmem_size
was being capped. I tested it on a 8.0-prerel server with 8G of ram,
kmem_size set to 20G in the loader but the resulting kmem_size was less than
4G before the patch. Now it is 20G. So, I'm not sure it calculates it properly?
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