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Date:      Fri, 17 Jan 2014 09:47:56 -0500 (EST)
From:      Rick Macklem <rmacklem@uoguelph.ca>
To:        Daniel Braniss <danny@cs.huji.ac.il>
Cc:        FreeBSD stable <freebsd-stable@freebsd.org>
Subject:   Re: on 9.2-stable nfs/zfs and 10g hang
Message-ID:  <588564685.11730322.1389970076386.JavaMail.root@uoguelph.ca>
In-Reply-To: <012BE46A-DA0F-422F-85D0-8C1E71BC3C51@cs.huji.ac.il>

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Daniel Braniss wrote:
> hi all,
>=20
> All was going ok till I decided to connect this host via a 10g nic
> and very soon it started
> to hang. Running multiple make buildworlds from other hosts connected
> via 10g and
> using both src and obj on the server via tcp/nfs did ok. but running
> =09find =E2=80=A6 -exec md5 {} + (the find finds over 6M files)
> from another host (at 10g) will hang it very quickly.
>=20
> If I wait a while (can=E2=80=99t be more specific) it sometimes recovers =
-
> but my users are not very
> patient :-)
>=20
This suggests that an RPC request/reply gets dropped in a way that TCP
doesn't recover. Eventually (after up to about 15min, I think?) the TCP
connection will be shut down and a new TCP connection started, with a
retry of outstanding RPCs.

> I will soon try the same experiment using the old 1G nic, but in the
> meantime, if someone
> could shed some light would be very helpful
>=20
> I=E2=80=99m attaching core.txt, but if it doesn=E2=80=99t make it, it=E2=
=80=99s also
> available at:
> =09ftp://ftp.cs.huji.ac.il/users/danny/freebsd/core.txt.16
>=20
You might try disabling TSO on the net interface. There are been issues
with TSO for segments around 64K in the past (or use rsize=3D32768,wsize=3D=
32768
options on the client mount, to avoid RPCs over about 32K in size).

Beyond that, capturing a packet trace for the case that hangs easily and
looking at what goes on near the end of it in wireshark might give you
a hint about what is going on.

rick

> thanks,
> =09danny
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>=20



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