Sudden Reboots

[Jim Durham]

On Friday 01 October 2004 12:36 pm, Doug Ambrisko wrote:
> Jim Durham writes:
> | I have had this problem now with at least 3 FreeBSD servers over a period
> | of about 2 years. I had put it down to some hardware problem but it seems
> | to be too much of a coincidence with 3 different machines doing the same
> | thing.
> |
> | The first time was when I put 4.5-RELEASE on a brand new Dell Poweredge
> | 2650. I ran it on the bench for a week or so, then decided all was well
> | and put it in the server rack and started doing the company's email
> | service on it. After a few weeks, it suddenly would 'reboot' for no
> | apparent reason. No log entries, nothing at all except the usual stuff in
> | /var/log/messages about '/ was not unmounted correctly', etc. Just like
> | you had pulled the power plug.
>
> How much memory are in these system?. 
The Dell is a Dual Xeon 2650 with 2gb or Ram. The ISP's box has only 256 megs 
or ram and the business customer's box has 512.

> If you have 3G or more you end 
> up with very little left for the kernel in the 2G space

Can you elaborate on why this is?

> .  You can 
> monitor how much space you have left by compile a debug kernel then
> as root:
>  gdb -k kernel.debug /dev/mem
>  print ((unsigned int)virtual_end)-((unsigned int)kernel_vm_end)
> This should probably be made into a sysctl so it can be montored
> better.
>
> If you only have a few meg. left it doesn't take many processes to
> fork etc. then you machine blows up.  The bge driver for example takes
> 4M each for the jumbo packet handling.  You can recover some of this
> memory via loader.conf tunables or bump KVA_PAGES in your kernel
> config file.  Still once this memory is put into the zone allocator
> (vmstat -z) in -stable it is gone from the system even if that bucket
> isn't fully used or needed :-(

What would you expect to see in the logs on such a scenario? I'm surprised to 
see nothing.
>
> Ironically the more memory you put in a system the less you can do with
> the system!
>
> A lot of people are starting to run into this problem since large memory
> machines are cheap.

Well, I don't think 2gb is large by your standards?
>
> Doug A.
-- 
-Jim