Re: Another hang...

[David Brownlee <abs%NetBSD.org@localhost>]

On Fri, 23 Jan 2009, Greg A. Woods; Planix, Inc. wrote:

> On 23-Jan-2009, at 9:00 AM, Johnny Billquist wrote:
> > Compared to the first hang, this is in a way inverted. First hang it didn't 
> > respond to pings, but I could break into ddb. This time it responds to 
> > pings, but I can't break into ddb.
>
> Oddly this sounds very much like the kinds of bizarre behaviour I would see 
> on my i386 server when it was running out of kernel memory.  Kernel memory is 
> very restricted on i386, even if the machine has 4GB or more RAM (which is 
> why I tried to use Alphas for all my servers which need 4GB or more RAM).
>
> My solution on i386 was to restrict BUFCACHE to 10% which, IIUC, keeps the 
> number of buffer headers low enough that they don't squeeze the kernel for 
> too much memory.
>
> You might also want to reduce kern.maxvnodes and/or any other tuning variable 
> that might affect performance but which won't cause actual operations 
> problems (eg. don't reduce NMBCLUSTERS if the machine handles lots of network 
> traffic as not having enough memory dedicated to networking, especially with 
> NFS, will also cause actual failures, not just degraded performance).

        I wonder if there is some issue where some resource is not being
        freed fast - on faster platforms its much harder to trigger the
        issue, but on the vax its much easier...

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                David/absolute       -- www.NetBSD.org: No hype required --