Adam could well be on the right track: if this application is the
type to create new threads/processes for each network connection and
you aren't getting good i/o throughput, it can start a chain of events
that leads to the symptom you are seeing:
many network connections ("processes"), not getting serviced ->
more elements in the run queue & memory bloat ->
high load averages (too many jobs in the run queue ->
Linux kernel will start refusing network connections.
When you can get back in to the guest, take a look in the syslog
and see if you see messages refering to things like connection refused
due to high load averages and the inability to fork a new process, etc.
I have seen this happen, even when there was plenty of real memory
available: sometimes the "memory shortage" is in kernel buffers, etc.
not in overall system memory. It was caused by too high a rate of
inbound connections.
There are several Linux kernel tuning parameters, check out the
"sysctl" command. IF your problem is similiar to the ones I have
seen, you want to look especially closesly at the "net.core.<blah>" and
"net.ipv4.<blah>" parms.
> -----Original Message-----
> From: Adam Thornton [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, July 14, 2004 02:07 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Network freezes
>
> On Wed, 2004-07-14 at 03:43, Sebastian Korte wrote:
> > I often read this hint on the mailinglist to reduce memory, but what if the
> > application (SAP) needs it? Two days ago my guest2 got stuck because mem and
> > swap was 100% used and it began to kill processes to free memory. I thought
> > I have to add mem and swap...
>
> Both of your guests have about 400MB effectively free right now. If
> that's when SAP is quiescent, then that might be the right amount of
> memory. You certainly have a lot of swap. I would suggest putting swap
> on VDISK on each guest at a higher priority than its swap on regular
> DASD, though. I think I'd also reduce each machine by about 300MB.
>
> > And: it doesn't get stuck. It's alive. I only cannot do any networking with
> > it.
>
> You're running z/VM 4.4, right? Try giving IOPRIORITY (I think that's
> what it is) a boost in the directory entry.
>
> Adam
>
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