From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Mon, 26 Oct 2009 16:53:21 -0400
To: 9fans@9fans.net
Message-ID: <8430a4bb32e0ad61f7680a0210d91fdd@brasstown.quanstro.net>
In-Reply-To: <<4B4622FF-CD80-4466-9D07-316E2835D10F@pvv.ntnu.no>>
References: <<4B4622FF-CD80-4466-9D07-316E2835D10F@pvv.ntnu.no>>
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Subject: Re: [9fans] soverflow for fx->in
Topicbox-Message-UUID: 908d6e0e-ead5-11e9-9d60-3106f5b1d025

On Mon Oct 26 12:35:07 EDT 2009, andreer@pvv.ntnu.no wrote:
> Our cpu/auth/file went belly up some time during the weekend. It
> responded to ping, but we couldn't drawterm in. No response from
> the vblade process providing storage to our XenServers either.
> Walking down to the machine I found the screen full of "soverflow
> for fx->in" messages. I had to reboot it to get the virtual machines
> back online, so this is my only clue (print statement in
> /sys/src/9/pc/devether.c:186 ). The machine had been working happily
> for over a week before this. Any ideas as to how i can keep this
> from happening again?
>
> The ethernet controller is an "Intel®PRO/1000 GT Desktop Adapter"
> according to the sticker on the back, on bootup i get
> #l0: i82543: 1000 Mbps port 0xFEBE0000 irq 5 tu 1514:000e0c73d17a

a soft overflow is when there are packets coming in
that don't fit on the ethernet queue.  soft overflows
are not bugs.  it's a consequence of having a finite
memory; one cannot queue infinitely.

however, printing each soft overflow to the console
can put one in a difficult to recover from situation.
i would suggest reverting these changes

; diff -c /n/sourcesdump/2009/0601/plan9/sys/src/9/pc/devether.c /n/sourcesdump/2009/0404/plan9/sys/src/9/pc/devether.c
/n/sourcesdump/2009/0601/plan9/sys/src/9/pc/devether.c:182,196 - /n/sourcesdump/2009/0404/plan9/sys/src/9/pc/devether.c:182,192
  				else if(xbp = iallocb(len)){
  					memmove(xbp->wp, pkt, len);
  					xbp->wp += len;
- 					if(qpass(f->in, xbp) < 0) {
- 						print("soverflow for f->in\n");
+ 					if(qpass(f->in, xbp) < 0)
  						ether->soverflows++;
- 					}
  				}
- 				else {
- 					print("soverflow iallocb\n");
+ 				else
  					ether->soverflows++;
- 				}
  			}
  			else
  				etherrtrace(f, pkt, len);
/n/sourcesdump/2009/0601/plan9/sys/src/9/pc/devether.c:198,207 - /n/sourcesdump/2009/0404/plan9/sys/src/9/pc/devether.c:194,201
  	}

  	if(fx){
- 		if(qpass(fx->in, bp) < 0) {
- 			print("soverflow for fx->in\n");
+ 		if(qpass(fx->in, bp) < 0)
  			ether->soverflows++;
- 		}
  		return 0;
  	}
  	if(fromwire){
/n/sourcesdump/2009/0601/plan9/sys/src/9/pc/devether.c:239,246 - /n/sourcesdump/2009/0404/plan9/sys/src/9/pc/devether.c:233,238
  	}

  	if(!loopback){
- 		if(qfull(ether->oq))
- 			print("etheroq: WARNING: ether->oq full!\n");
  		qbwrite(ether->oq, bp);
  		if(ether->transmit != nil)
  			ether->transmit(ether);


- erik