Date:	Sat, 18 Jul 2009 09:14:18 +0200
From:	Jesper Dangaard Brouer <hawk@...x.dk>
To:	Willy Tarreau <w@....eu>
Cc:	Bill Fink <billfink@...dspring.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Robert Olsson <Robert.Olsson@...a.slu.se>,
	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>,
	"Ronciak, John" <john.ronciak@...el.com>,
	jesse.brandeburg@...el.com,
	Stephen Hemminger <shemminger@...tta.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Achieved 10Gbit/s bidirectional routing

On Fri, 2009-07-17 at 22:35 +0200, Willy Tarreau wrote:
> On Thu, Jul 16, 2009 at 11:38:27AM -0400, Bill Fink wrote:
> > On Thu, 16 Jul 2009, Jesper Dangaard Brouer wrote:
> > 
> > > On Wed, 2009-07-15 at 23:22 -0400, Bill Fink wrote:
> > > > On Wed, 15 Jul 2009, Jesper Dangaard Brouer wrote:
> > > > 
> > > > > I'm giving a talk at LinuxCon, about 10Gbit/s routing on standard
> > > > > hardware running Linux.
> > > > > 
> > > > >   http://linuxcon.linuxfoundation.org/meetings/1585
> > > > >   https://events.linuxfoundation.org/lc09o17
> > > > > 
> > > > > I'm getting some really good 10Gbit/s bidirectional routing results
> > > > > with Intels latest 82599 chip. (I got two pre-release engineering
> > > > > samples directly from Intel, thanks Peter)
> > > > > 
> > > > > Using a Core i7-920, and tuning the memory according to the RAMs
> > > > > X.M.P. settings DDR3-1600MHz, notice this also increases the QPI to
> > > > > 6.4GT/s.  (Motherboard P6T6 WS revolution)
> > > > > 
> > > > > With big 1514 bytes packets, I can basically do 10Gbit/s wirespeed
> > > > > bidirectional routing.
> > > > > 
> > > > > Notice bidirectional routing means that we actually has to move approx
> > > > > 40Gbit/s through memory and in-and-out of the interfaces.
> > > > > 
> > > > > Formatted quick view using 'ifstat -b'
> > > > > 
> > > > >   eth31-in   eth31-out   eth32-in  eth32-out
> > > > >     9.57  +    9.52  +     9.51 +     9.60  = 38.20 Gbit/s
> > > > >     9.60  +    9.55  +     9.52 +     9.62  = 38.29 Gbit/s
> > > > >     9.61  +    9.53  +     9.52 +     9.62  = 38.28 Gbit/s
> > > > >     9.61  +    9.53  +     9.54 +     9.62  = 38.30 Gbit/s
> > > > > 
> > > > > [Adding an extra NIC]
> > > > > 
> > > > > Another observation is that I'm hitting some kind of bottleneck on the
> > > > > PCI-express switch.  Adding an extra NIC in a PCIe slot connected to
> > > > > the same PCIe switch, does not scale beyond 40Gbit/s collective
> > > > > throughput.
> > > 
> > > Correcting my self, according to Bill's info below.
> > > 
> > > It does not scale when adding an extra NIC to the same NVIDIA NF200 PCIe
> > > switch chip (reason explained below by Bill)
> > > 
> > >  
> > > > > But, I happened to have a special motherboard ASUS P6T6 WS revolution,
> > > > > which has an additional PCIe switch chip NVIDIA's NF200.
> > > > > 
> > > > > Connecting two dual port 10GbE NICs via two different PCI-express
> > > > > switch chips, makes things scale again!  I have achieved a collective
> > > > > throughput of 66.25 Gbit/s.  This results is also influenced by my
> > > > > pktgen machines cannot keep up, and I'm getting closer to the memory
> > > > > bandwidth limits.
> > > > > 
> > > > > FYI: I found a really good reference explaining the PCI-express
> > > > > architecture, written by Intel:
> > > > > 
> > > > >  http://download.intel.com/design/intarch/papers/321071.pdf
> > > > > 
> > > > > I'm not sure how to explain the PCI-express chip bottleneck I'm
> > > > > seeing, but my guess is that I'm limited by the number of outstanding
> > > > > packets/DMA-transfers and the latency for the DMA operations.
> > > > > 
> > > > > Does any one have datasheets on the X58 and NVIDIA's NF200 PCI-express
> > > > > chips, that can tell me the number of outstanding transfers they
> > > > > support?
> > > > 
> > > > We've achieved 70 Gbps aggregate unidirectional TCP performance from
> > > > one P6T6 based system to another.  We figured out in our case that
> > > > we were being limited by the interconnect between the Intel X58 and
> > > > Nvidia N200 chips.  The first 2 PCIe 2.0 slots are directly off the
> > > > Intel X58 and get the full 40 Gbps throughput from the dual-port
> > > > Myricom 10-GigE NICs we have installed in them.  But the other
> > > > 3 PCIe 2.0 slots are on the Nvidia N200 chip, and I discovered
> > > > through googling that the link between the X58 and N200 chips
> > > > only operates at PCIe x16 _1.0_ speed, which limits the possible
> > > > aggregate throughput of the last 3 PCIe 2.0 slots to only 32 Gbps.
> > > 
> > > This definitly explains the bottlenecks I have seen! Thanks!
> > > 
> > > Yes, it seems to scale when installing the two NICs in the first two
> > > slots, both connected to the X58.  If overclocking the RAM and CPU a
> > > bit, I can match my pktgen machines speed which gives a collective
> > > throughput of 67.95 Gbit/s.
> > > 
> > >    eth33          eth34          eth31         eth32
> > >  in     out     in     out     in    out     in    out 
> > > 7.54 + 9.58  + 9.56 + 7.56  + 7.33 + 9.53 + 9.50 + 7.35  = 67.95 Gbit/s
> > > 
> > > Now I just need a faster generator machine, to find the next bottleneck ;-)
> > > 
> > > 
> > > > This was clearly seen in our nuttcp testing:
> > > > 
> > > > [root@...aid-1 ~]# ./nuttcp-6.2.6 -In2 -xc0/0 -p5001 192.168.1.11 & ./nuttcp-6.2.6 -In3 -xc0/0 -p5002 192.168.2.11 & ./nuttcp-6.2.6 -In4 -xc1/1 -p5003 192.168.3.11 & ./nuttcp-6.2.6 -In5 -xc1/1 -p5004 192.168.4.11 & ./nuttcp-6.2.6 -In6 -xc2/2 -p5005 192.168.5.11 & ./nuttcp-6.2.6 -In7 -xc2/2 -p5006 192.168.6.11 & ./nuttcp-6.2.6 -In8 -xc3/3 -p5007 192.168.7.11 & ./nuttcp-6.2.6 -In9 -xc3/3 -p5008 192.168.8.11
> > > > n2: 11505.2648 MB /  10.09 sec = 9566.2298 Mbps 37 %TX 55 %RX 0 retrans 0.10 msRTT
> > > > n3: 11727.4489 MB /  10.02 sec = 9815.7570 Mbps 39 %TX 44 %RX 0 retrans 0.10 msRTT
> > > > n4: 11770.1250 MB /  10.07 sec = 9803.9901 Mbps 39 %TX 51 %RX 0 retrans 0.10 msRTT
> > > > n5: 11837.9320 MB /  10.05 sec = 9876.5725 Mbps 39 %TX 47 %RX 0 retrans 0.10 msRTT
> > > > n6:  9096.8125 MB /  10.09 sec = 7559.3310 Mbps 30 %TX 32 %RX 0 retrans 0.10 msRTT
> > > > n7:  9100.1211 MB /  10.10 sec = 7559.7790 Mbps 30 %TX 44 %RX 0 retrans 0.10 msRTT
> > > > n8:  9095.6179 MB /  10.10 sec = 7557.9983 Mbps 31 %TX 33 %RX 0 retrans 0.10 msRTT
> > > > n9:  9075.5472 MB /  10.08 sec = 7551.0234 Mbps 31 %TX 33 %RX 0 retrans 0.11 msRTT
> > > > 
> > > > This used 4 dual-port Myricom 10-GigE NICs.  We also tested with
> > > > a fifth dual-port 10-GigE NIC, but the aggregate throughput stayed
> > > > at about 70 Gbps, due to the performance bottleneck between the
> > > > X58 and N200 chips.
> > > 
> > > This is also very excellent results!
> > > 
> > > Thanks a lot Bill !!!
> > 
> > We also achieved nearly 80 Gbps in bidirectional TCP tests (40 Gbps
> > simultaneously in each direction):
> > 
> > [root@...aid-1 ~]# ./nuttcp-6.2.6 -In2 -xc0/0 -p5001 192.168.1.11 & ./nuttcp-6.2.6 -In3 -r -xc0/0 -p5002 192.168.2.11 & ./nuttcp-6.2.6 -In4 -xc1/1 -p5003 192.168.3.11 & ./nuttcp-6.2.6 -In5 -r -xc1/1 -p5004 192.168.4.11 & ./nuttcp-6.2.6 -In6 -xc2/2 -p5005 192.168.5.11 & ./nuttcp-6.2.6 -In7 -r -xc2/2 -p5006 192.168.6.11 & ./nuttcp-6.2.6 -In8 -xc3/3 -p5007 192.168.7.11 & ./nuttcp-6.2.6 -In9 -r -xc3/3 -p5008 192.168.8.11                                    
> > n2: 11542.6250 MB /  10.07 sec = 9619.9920 Mbps 44 %TX 51 %RX 0 retrans 0.12 msRTT                                                                      
> > n3: 11543.7143 MB /  10.06 sec = 9622.2153 Mbps 41 %TX 49 %RX 0 retrans 0.15 msRTT                                                   
> > n4: 11622.8125 MB /  10.05 sec = 9701.0296 Mbps 43 %TX 51 %RX 0 retrans 0.10 msRTT                                                                      
> > n5: 11523.6875 MB /  10.03 sec = 9638.8883 Mbps 43 %TX 50 %RX 0 retrans 0.15 msRTT                                                                      
> > n6: 11608.0141 MB /  10.04 sec = 9695.7388 Mbps 43 %TX 50 %RX 0 retrans 0.10 msRTT                                                                      
> > n7: 11580.1250 MB /  10.04 sec = 9679.3910 Mbps 43 %TX 50 %RX 0 retrans 0.13 msRTT                                                                      
> > n8: 11608.0000 MB /  10.06 sec = 9678.7596 Mbps 42 %TX 50 %RX 0 retrans 0.10 msRTT                                                                      
> > n9: 11553.3750 MB /  10.05 sec = 9643.7296 Mbps 45 %TX 50 %RX 0 retrans 0.11 msRTT                                                                      
> > 
> > This was using 2 dual-port 10-GigE NICs in the first two PCIe 2.0 slots.
> > We are using an Intel i7 965 quad-core 3.2 GHz Nehalem processor
> > (overclocked to 3.4 GHz) and 2000 MHz DDR3 memory.  Adding an additional
> > dual-port 10-GigE NIC on the Nvidia N200 chip does only marginally
> > better, as it appears we are basically CPU limited at this point for
> > this test (the sum of the TX and RX CPU utilization for each pair of
> > 10-GigE interfaces is about 93%).
> 
> Hey guys, those are really nice numbers. Since TCP splicing appeared in the
> kernel (once we got it fixed), I achieved 10 Gbps of HTTP proxying using
> haproxy with very low CPU usage (about 20% of a Core2Duo 2.66 GHz).

Nice, but I think we have a bug with the measured CPU usage.  Eric
Dumazet did a fix, but also pointed out that in a later mail, at I seem
like it not fixed completely yet...

> Before buying the machines, I had been wandering around with the NICs
> donated by Myricom in order to try to find a machine capable of supporting
> this. My conclusion was that a lot of machines had difficulties getting
> above 3.5, 4.7 and 6.5 Gbps of output traffic (those 3 numbers were always
> the same, depending on the chipsets). There clearly was a bandwidth
> limitation imposed by the chipset.
> 
> So I waited for the X38 and AM780FX chipsets to become available and
> bought 3 machines (1 C2D, 1 AMD X2, 1 AMD X4). Those ones have no problem
> with 10 Gbps of forwarded traffic (20 Gbps of total bus bandwidth), even
> with 1500 bytes frames, but I don't know how high they can go, maybe
> they will saturate slightly above.

My experience is also that the AMDs can easily do 10Gbit/s forwarding,
but doing bidirectional they suffer...


> Unfortunately, I only have 5 NICs in 3 machines and no switch (and CX4
> is hard to find these days), so I'm probably stuck at 10 Gbps max.

We are a fiber company, so I'm using our spare 10G optics, but I'm
limited by our supply of SFP+ currently.

I'll be getting two 6 port 10GbE NIC using PCIe2 x16 82599, in august,
so it will be interesting how high we can go! :-)

> Interestingly, I had the impression that forwarding data with TCP
> splicing costs less CPU than IP forwarding, because the NICs can do
> LRO.
> 
> Also, I know a french service provider who uses haproxy on Core i7
> machines and who has already reached 5 Gbps of sustained traffic
> with recent intel dual-port NICs (though I'm not sure exactly which
> ones). This is with very little CPU usage too, less than 2-3% user
> and 15% system+softirq. On previous machines (quad core xeons), it
> was impossible to go beyond 3 Gbps, it looked like the chipset was
> the limitating factor too (though I don't precisely remember which
> one it was).
> 
> I really blamed the NICs because this guys machine was about 4 times
> more powerful than mine, but apparently it was just a chipset issue.
> 
> I also happen to have a customer who recently received a few Sun NXGE,
> mounted in Sun x2100-m2 using an nvidia chipset which I tested OK at
> 10 Gbps with my myri10GE NICs. I'll try to see if I can run some tests
> there, as Davem once said those NICs are really good too.

The Sun NIU NIC has to use several hardware queues to achieve 10GbE.
Currently using these as generators, and thats one of my limiting
factors.

> All in all, I find it really cool that our beloved OS scales that
> well with the hardware :-)

Yes, its really amazing how well the Linux net stack scales.  I think
the primary thanks for this efford goes to DaveMs multiqueue changes and
Eric Dumazet's tuning.

ps. I'll offline untill tuesday.
-- 
Med venlig hilsen / Best regards
  Jesper Brouer
  ComX Networks A/S
  Linux Network developer
  Cand. Scient Datalog / MSc.
  Author of http://adsl-optimizer.dk
  LinkedIn: http://www.linkedin.com/in/brouer

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