Re: zonelimit issues...

On Mon, Apr 21, 2008 at 05:16:28PM +0900, gnn@xxxxxxxxxxx wrote:

At Mon, 21 Apr 2008 16:46:00 +0900,
gnn@xxxxxxxxxxx wrote:

At Sun, 20 Apr 2008 10:32:25 +0100 (BST),
rwatson wrote:


On Fri, 18 Apr 2008, gnn@xxxxxxxxxxx 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.

There is no cluster/mbuf leak.

The problem that FreeBSD has small KVA space: only 2G even on amd64 32G
machines.

So with

vm.kmem_size=1G
# 64M KVA
kern.maxbcache=64M
# 4M KVA
kern.ipc.maxpipekva=4M


I can use something like this:

# 256M KVA/KVM
kern.ipc.nmbjumbop=64000
# 216M KVA/KVM
kern.ipc.nmbclusters=98304
# 162M KVA/KVM
kern.ipc.maxsockets=163840
# 8M KVA/KVM
net.inet.tcp.maxtcptw=163840
# 24M KVA/KVM
kern.maxfiles=204800


--
Igor Sysoev
http://sysoev.ru/en/
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