zonelimit issues...

[gnn at freebsd.org]

At Mon, 21 Apr 2008 16:46:00 +0900,
gnn at freebsd.org wrote:
> 
> At Sun, 20 Apr 2008 10:32:25 +0100 (BST),
> rwatson wrote:
> > 
> > 
> > On Fri, 18 Apr 2008, gnn at freebsd.org wrote:
> > 
> > > I am wondering why this patch was never committed?
> > >
> > > http://people.freebsd.org/~delphij/misc/patch-zonelimit-workaround
> > >
> > > It does seem to address an issue I'm seeing where processes get into the 
> > > zonelimit state through the use of mbufs (a high speed UDP packet receiver) 
> > > but even after network pressure is reduced/removed the process never gets 
> > > out of that state again.  Applying the patch fixed the issue, but I'd like 
> > > to have some discussion as to the general merits of the approach.
> > >
> > > Unfortunately the test that currently causes this is tied very tightly to 
> > > code at work that I can't share, but I will hopefully be improving mctest to 
> > > try to exhibit this behavior.
> > 
> > When you take all load off the system, do mbufs and clusters get properly 
> > freed back to UMA (as visible in netstat -m)?  If not, continuing to bump up 
> > against the zonelimit would suggest an mbuf/cluster leak, in which case we 
> > need to track that bug.
> > 
> 
> This is unclear as the process that creates the issue opens 50 UDP
> multicast sockets with very large socket buffers.  I am investigating
> this aspect some more.
> 

OK, yes, the clusters etc. go back to normal when the incoming
pressure is released.  I do not believe we have a cluster/mbuf leak.

Best,
George