Re: [Backtrace] 4.9 and 5.1-RELEASE occasionly panic on RAM > 4GB without PAE (long)

On Thu, Dec 18, 2003 at 08:40:45AM +0800, Xin LI/???? wrote:
> Hello,
> 
> One of my friend is operating servers on a big ICP in China. They found that
> if they run FreeBSD 4.9 or FreeBSD 5.1-RELEASE on their server, which has
> more than 4GB RAM installed, then they will occasionaly have the server
> panic'ed, or even rebooted without any reason.
> 
> The server hardware is: P4-Xeon-2.4G*2, 4G RAM(DDR266), 146G*2 on asr(4)
> RAID-1. The kernel is not quite different from GENERIC, except that we have
> AUTO_EOI1 enabled. When PAE is enabled, then the kernel will not recognize
> the asr(4) device, and thus would refuse to boot from it, so we have it
> disabled.
> 
>  
> This problem afffects 4.9-RELEASE and 5.1-RELEASE. As the ICP is a
> conservative user, they will not run -STABLE, nor -CURRENT. I have turned
> the debugging symbols on their server and grabbed the following backtraces.
> Also, I have found how to reproduce this problem on a machine running with >
> 4GB memory without a PAE configuration, which, in my opinion, should not
> cause a kernel panic because it's just a resource hungry program and all it
> will do should, at most, hang the system, or even being killed directly by
> the operating system.

Without PAE you can't use more than 4G on i386.
You either have to use PAE or limit memory to 4G.
This is strictly a hardware limitation there no other option left.
The best that can be done would be autolimiting available memory
instead of panicing later.
I don't know how difficult this would be to implement.
Telling in which way it panics if you try to do something that your
hardware can't do is just wasted time.

If PAE isn't compatible with asr(4) then maybe it's not busdma'ed
or buggy.
With PAE you have to use busdma aware drivers.
That's a software thing and can be fixed.

-- 
B.Walter                   BWCT                http://www.bwct.de
ticso_at_bwct.de                                  info_at_bwct.de