Re: panic: kmem_malloc(131072): kmem_map too small (AMD64)

On Mon, 24 Sep 2007, Scott Long wrote:

> Ruslan Ermilov wrote:
>> On Mon, Sep 24, 2007 at 08:04:33AM -0500, Larry Rosenman wrote:
>>> On Mon, 24 Sep 2007, Kris Kennaway wrote:
>>> 
>>>> Ruslan Ermilov wrote:
>>>>> On Sat, Sep 22, 2007 at 11:37:37PM +0200, Kris Kennaway wrote:
>>>>>> Darren Reed wrote:
>> [...]
>>>>>>> Stupid question, perhaps, but is vm.kmem_size/vm.kmem_size_max limited 
>>>>>>> by physical RAM?
>>>>>> Yes.
>>>>> To be precise, it's actually limited by 2 * sizeof(physical RAM).
>>>>> It's still size of a _virtual_ memory map (kmem_map), after all:
>>>>> :	/*
>>>>> : 	 * 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;
>>>> Well OK, but that seems pretty dangerous, because it leaves open a 
>>>> pathway to exhaust all of physical memory and presumably panic.
>>> is KVA pageable?  Is the kmem_map dedicating non-pageable memory?
>>> 
>> kmem_map is used to map memory for the zone allocator, including
>> malloc(9).
>> 
>>> I've set my vm.kmem_max to 1G, (on a 4G amd64 box).  Is that reasonable?
>>> 
>> It just means that your kernel can "malloc" up to 1G of memory.
>> 
>
> You're all missing the point, I hate to say.  What happened is that a change 
> was made recently to more accurately account for allocated
> memory.  Now people are getting kmem_map_too_small panics that weren't
> getting them before.  So while the accounting is now more accurate, the
> outcome is actually harmful.  That needs to be fixed before the release.
>

How can I help, and what's a proposed patch?

LER

> Scott
>
>
>

-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 512-248-2683                 E-Mail: ler_at_lerctr.org
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