On 11.03.2013 17:05, Garrett Wollman wrote:
In article <513db550.5010...@freebsd.org>, an...@freebsd.org writes:
Garrett's problem is receive side specific and NFS can't do much about it.
Unless, of course, NFS is holding on to received mbufs for a longer time.
Well, I have two problems: one is running out of mbufs (caused, we
think, by ixgbe requiring 9k clusters when it doesn't actually need
them), and one is livelock. Allowing potentially hundreds of clients
to queue 2 MB of requests before TCP pushes back on them helps to
sustain the livelock once it gets started, and of course those packets
will be of the 9k jumbo variety, which makes the first problem worse
as well.
I think that TCP, or rather the send socket buffer, currently doesn't
push back at all but simply accepts everything that gets thrown at it.
This obviously is a problem and the NFS server seems to depend somewhat
on that by requiring atomicity on a RPC send. I have to trace the mbuf
path through NFS to the socket to be sure. The code is slightly opaque
though.
--
Andre
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