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Date:      Fri, 20 Apr 2018 16:45:23 -0700
From:      Kevin Bowling <kevin.bowling@kev009.com>
To:        Garrett Wollman <wollman@bimajority.org>
Cc:        FreeBSD Net <freebsd-net@freebsd.org>
Subject:   Re: Diagnosing terrible ixl performance
Message-ID:  <CAK7dMtDpw-9Xi39w_DAzAfJcrZz5H4Lxxiesow1b2BPR1P6PBw@mail.gmail.com>
In-Reply-To: <23257.26265.720293.659892@hergotha.csail.mit.edu>
References:  <23257.26265.720293.659892@hergotha.csail.mit.edu>

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These are all pretty much known (to intel and NF/LLNW) issues with the
ixl driver.  If you must run 11.1 you are best off just buying a
chelsio T580.

If you can run HEAD, or perhaps an eventual 11.3 MFC,
https://github.com/intel-wired-ethernet/freebsd/tree/ixl-iflib may fix
this but there are a few remaining issues before that hits HEAD.

Regards,

On Thu, Apr 19, 2018 at 9:03 PM, Garrett Wollman <wollman@bimajority.org> wrote:
> I'm commissioning a new NFS server with an Intel dual-40G XL710
> interface, running 11.1.  I have a few other servers with this
> adapter, although not running 40G, and they work fine so long as you
> disable TSO.  This one ... not so much.  On the receive side, it gets
> about 600 Mbit/s with lots of retransmits.  On the *sending* side,
> though, it's not even able to sustain 10 Mbit/s -- but there's no
> evidence of retransmissions, it's just sending really really slowly.
> (Other machines with XL710 adapters are able to sustain full 10G.)
> There is no evidence of any errors on either the adapter or the switch
> it's connected to.
>
> So far, I've tried:
>
> - Using the latest Intel driver (no change)
> - Using the latest Intel firmware (breaks the adapter)
> - Disabling performance tweaks in loader.conf and sysctl.conf
> - Changing congestion-control algorithms
>
> Anyone have suggestions while I still have time to test this?  (My
> plan B is to fall back to an X520 card that I have in my spares kit,
> because I *know* those work great with no faffing about.)  Any
> relevant MIBs to inspect?
>
> The test I'm doing here is simple iperf over TCP, with MTU 9120.  It
> takes about 10 seconds for the sending side to complete, but buffers
> are severely constipated for 20 seconds after that (delaying all
> traffic, including ssh connections).
>
> I'm at the point of trying different switch ports just to eliminate
> that as a possibility.
>
> -GAWollman
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