Date: Sun, 25 Apr 2021 13:06:11 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: Chris Roose <chrisroose@fastmail.com>, "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Cc: Juraj Lutter <otis@freebsd.org> Subject: Re: NFS issues since upgrading to 13-RELEASE Message-ID: <YQXPR0101MB09685508380CC691A95898BDDD439@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM> In-Reply-To: <089ce08a-1c77-b7a5-4e20-b1c22df23176@fastmail.com> References: <CABW2x9ooC0w4_50Rd3XfLQdKXrUtJEty6mbYmyMSAk7%2BWyyDpA@mail.gmail.com>, <089ce08a-1c77-b7a5-4e20-b1c22df23176@fastmail.com>
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Chris Roose wrote:
> Jason Unovitch wrote:
> > Does anything change if you set -tso -lro on the serving NIC on your
> > FreeBSD server side? Do the Linux clients remain responsive then?
>
> Thank you, Jason. This seems to have cleared the problem up for me.
> Since disabling TSO and LRO on the server NIC last night, I haven't seen
> any timeouts.
I think there might be a couple of reasons that disabling TSO resolves this:
1 - The obvious one is that the net chip/driver is broken for certain TSO
segments. Often the culprit is a NFS read reply of just less than 64K,
that is made up of a chain of 33mbufs with a total length just under
64K. Then the driver adds a MAC layer header that bumps the size up
to greater than 64K.
--> This can happen if the driver does not set the TSO sizing parameters
quite correctly, among other things.
2 - TSO does work correctly, but results in different timing of the TCP
segments transmitted for the segment compared with non-TSO.
I believe that, for otis@, disabling TSO reduced the frequency of Linux
client hangs, but did not stop them.
--> reverting the patch in r367492 (this patch is not in FreeBSD12) has
fixed the problem for him.
rick
--
Chris
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