Re: MBuf clusters - what uses them?

[Paul Goyette <paul%whooppee.com@localhost>]

On Sat, 5 Apr 2014, Greg Troxel wrote:

> <snip>
>
> I see no fails counted.  Why do you think you are out of clusters?  Are
> you seeing that in dmesg?  Or is it just a possible lockup explanation?

The mbuf/mbufcluster "explanation" was offered when I first reported 
this several months ago.

> Please describe the lockup symptoms more precisely.

Most obvious symptom is sudden lack of network connectivity.  A ping to 
another host on the local network fails with a "no buffer space" error.

> Also, look in vmstat -m for anything with fail != 0.

No failures ever appear.

However, I have tracked mbuf usage via netstat and vmstat, and shortly 
before the lockup, both numbers showed a sudden increase in utilization.

> you might also save vmstat -m to a file every 5 minutes, and look
> before/after the next lockup.

Yeah, I was doing this every 1 minute...


Someone at that time suggested that bit-torrent could have been doing 
something nasty, so I stopped my "transmission" server.  The frequency 
of lockup has dropped dramatically, but not to zero.


Another symptom is with postfix...  It receives incoming mail from the 
network, but fails to forward the mail through my local dspam - mailq 
shows lots of messages in the "deferred" state due to "resources 
temporarily unavailable" errors.  (As near as I can tell, postfix uses 
unix-family sockets for this...)





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