Date: Fri, 20 Apr 2018 22:02:39 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: hiren panchasara <hiren@strugglingcoder.info>, Garrett Wollman <wollman@bimajority.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Diagnosing terrible ixl performance Message-ID: <YQBPR0101MB1042F7CBDE7B160E0CBDA148DDB40@YQBPR0101MB1042.CANPRD01.PROD.OUTLOOK.COM> In-Reply-To: <20180420212045.GB3653@strugglingcoder.info> References: <23257.26265.720293.659892@hergotha.csail.mit.edu>, <20180420212045.GB3653@strugglingcoder.info>
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I don't know if this post is helpful, but just in case: http://docs.FreeBSD.org/cgi/mid.cgi?04125f40-6388-f074-d935-ce6c16d220fa Hope you don't mind a top post, rick ________________________________________ From: owner-freebsd-net@freebsd.org <owner-freebsd-net@freebsd.org> on beha= lf of hiren panchasara <hiren@strugglingcoder.info> Sent: Friday, April 20, 2018 5:20:45 PM To: Garrett Wollman Cc: freebsd-net@freebsd.org Subject: Re: Diagnosing terrible ixl performance On 04/20/18 at 12:03P, Garrett Wollman 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. You are already trying to check if the switch in-between isn't causing the problem. A few other (probably obvious) things to try: - sysctl -a | grep hw.ixl or dev.ixl to see if you find anything useful (actual name might not be ixl, but you get the point) - Try with lower mtu to see if that's causing anything interesting - If you can reproduce easily, a single stream pcap might be useful from both send and recv side to understand the slowness. Cheers, Hiren
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