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One other point, these cloud companies like Amazon and Google do a great deal of self congratulations for some pretty embarrassing architectures. Necessitating million server datacenters is as WTF to me as being proud of millions of lines of code when someone else is doing it with magnitudes less. 40G networking has been commercially viable since the top of the decade and 100G (or partial variants) for a couple years now while ENA tops out at 20G. They are basically asleep at the wheel because their architectures are predicated on poor assumptions, shirking understanding of computer architecture for 10s of thousands of SREs and "full stack developers".

Dovetailing a bit, back in the commercial UNIX and mainframe markets it is pretty common to have 80%-90% percent system utilization. In the Linux world, it's usually single digits. For some reasons (I guess it's more inviting to think holistically due to the base OS model), we are getting those 90% figures in the BSD community. See drewg's comment, WhatsApp, Isilon, LLNW:

I led the creation of an OS team, to look from first principles, where we were spending CPU/bus/IO bandwidth, and focusing on north-south delivery instead of horizontal scale. A team of 5, we are able to deliver significant shareholder value http://investors.limelight.com/file/Index?KeyFile=38751761.

Yeah I suppose what I really want is physical procurement of hardware with the ease of cloud.

I haven't used them, but it looks compelling: https://www.packet.net/

>"One other point, these cloud companies like Amazon and Google do a great deal of self congratulations for some pretty embarrassing architectures. Necessitating million server datacenters is as WTF to me as being proud of millions of lines of code when someone else is doing it with magnitudes less"

Can you explain what these "embarrassing architectures"?

Also two of the largest tech companies on the planet using millions of servers is a "WTF" to you? Care to explain? Also I don't think either Amazon or Google has ever released actual numbers for server counts. Please provide a citation for this.

>"as being proud of millions of lines of code when someone else is doing it with magnitudes less"

This is also a pretty vague statement. Lines of code for what? And who is doing that same "what" with less code?

>"They are basically asleep at the wheel because their architectures are predicated on poor assumptions, shirking understanding of computer architecture for 10s of thousands of SREs and "full stack developers".

Do you really believe that Google and Amazon don't understand computer architecture?

Please provide citations for how you arrived at the at the number of SREs and "Full Stack Developers" at Google and Amazon. I don't think Google/Amazon even have "Full Stack Developer" as a job title.

>"I led the creation of an OS team, to look from first principles, where we were spending CPU/bus/IO bandwidth, and focusing on north-south delivery instead of horizontal scale"

You did this at Limelight Networks then I presume according to the link you provided? You realize that a CDN is predominantly North-South traffic right? CDNs are a very different business than being general purpose cloud providers which in addition to north-south traffic have substantial east-west traffic.

You fault Google and Amazon for "congratulating" themselves yet the link you provide presumably to substantiate your own grand achievements is fluffy press release. A press release with zero detail around the claims being made and no link to a white paper or any technical specifics are given.

Limelight is not exactly what I would call a market leader or a name associated with being a great technical innovator. Limelight lost 73 million dollars last years and has a 270 million market cap. They were also sued by CDN provider Akami and agreed to pay Akami licensing fees as part of the settlement for that infringement.[1]

>"A team of 5, we are able to deliver significant shareholder value"

Your company's stock trades at $2.56 a share while Amazon and Alphabets trade at well over $800 a share. I will gladly take the share holder value that Google's and Amazon's "10s of thousands of SREs and "full stack developers" provide over your team of 5.

[1] http://www.bizjournals.com/phoenix/news/2017/02/08/limelight...

Think about what this _means_, and let's be really conservative and assume a huge splay of 10 year old to current hw: 8 million cores, 10 million storage devices (100-1000x IOPS, 1-10x TB capacity), 8x recent global IP transit rate with just 2Gbit laggs. By the way, hyperscalers have many of these. That's enough compute to boil an ocean, at one datacenter. Now back at ya, go figure out the useful work per machine.

Google does pretty good in ecosystem investment. They do have people that know how computers work, and more importantly decision makers that let them pay huge dividends (i.e. containers vs VMs, CPU cache partitioning, TCP performance). I've seen little evidence of the same at Amazon.

Sorry, you can provide statistics that the majority of the 25k committers at one of these companies (ACM Queue monorepo article) are not toiling in a morass of overgrowth. People have told me things, YMMV, draw your own research and conclusions as I have mine.

That lawsuit was during a critical time. I can't comment any more there.

On GOOG, if you have enough money to make it worthwhile and want to ride a fractional increase above market growth rate, it's a safe stock, but it's not likely to to multiply over the next few years.

Again you have provided no citations for any of your figures or any of the hardware configurations you are stating, your just making things up it seems. This is gibberish.

Heh, anyone in the game knows the orders off hand. Try 10 seconds of google https://www.nextplatform.com/2015/04/09/how-in-hell-will-any...

This has been ongoing debate since the beginning. RDMA means running a large amount of protocol in silicon and firmware. Can you imagine what might go wrong?

In the FreeBSD community it is somewhat common knowledge that Chelsio is the best Ethernet vendor, mainly because their driver isn't a trainwreck like the dominant Intel (which share BSD HAL code on BSD/Linux/Illumos and are quite similar)

If you are alright with the trade offs of a firmware stack, Chelsio do have some pretty slick TCP full offloads that require no substantial application changes: http://www.chelsio.com/wp-content/uploads/resources/T6-100G-...

At the end of the day I think we will end up with RDMA being the norm. Additional offloads can only go so far and are going to require firmware anyway so why not just cut to the chase.

Last time I checked Chelsio backed iWarp which has pretty much been defeated in the RDMA wars by RoCE since iWarp had terrible performance because it has to run over TCP. Intel has even removed from it their new cards and have pushed DPDK as a replacement. I'm also not surprised Chelsio has added additional offloads to compensate for their lose. That being said RoCE does have that Converged Ethernet part (CE) which is still not mainstream in many datacenters.

I get people will be disappointed that their previously Open Source drivers will be replaced with proprietary firmware but as we see FPGAs take off I think that you may see VHDL code going open source on new fully programmable cards.

I for one welcome our new hardware based overlords but perhaps I'm being far to optimistic.

But why?

We are fairly confident we can make BSD pump several hundred Gbps doing real world long haul TCP for content serving in the next couple years on something like Naples or POWER9.

At the other end, Isilon converted from Infiniband to OS TCP for the latest product: https://www.nextplatform.com/2016/05/06/emc-shoots-explosive.... That is pretty amazing because of low latency timing and incast.

To your point, Intel's Altera acquisition may eventually bear fruit but I'm not holding my breath and don't really know how to reason about it until an offload/accelerator ecosystem is built up.

Now that I've reviewed the Chelsio doc more carefully I've noticed that DDP is actually part of iWarp so the TCP offload you mentioned is just one part of iWarp that happens to be transparent to user space which is quite interesting. That being said iWarp has lost out to RoCE mainly because of latency and not throughput. I guess that I'm just more biased towards lower latency (at the same bandwidth) because it is empirically better, even though for most applications 10us vs 1us is negligible. That and because I work in low latency trading.

It's kind of the other way around, TCP is done in silicon and firmware and passed up to the OS via a scatter-gather engine which is the core architectural feature. So iWARP lends itself to layering on the TOE, as do other higher level protocols like iSCSI and FCoE. DDP requires intertwining with the OS networking stack and VM but the card is able to DMA the data from the offloaded TCP stream right into the application's address space sockbuf.

I'm out of my league on extreme low latency stuff but take a look at http://www.chelsio.com/wp-content/uploads/resources/T6-WDLat.... For comparison sake, do you know the end to end latency of Mellanox RoCE?

Yeah my rather old ConnectX-3 Pro 40Gbe is crushing all these numbers for the given sizes of 16 to 1024.

ib_send_lat is 0.77, 0.77, 0.80, 0.86, 1.17, 1.31, 1.58

ib_write_lat is 0.73, 0.75, 0.76, 0.85, 1.12, 1.29, 1.57

ib_read_lat is 1.38, 1.38, 1.39, 1.42, 1.50, 1.65, 1.91

However it's really difficult to judge these things without a detailed description of the test setup. This is over physical loopback on a single machine and even things like cable length can skew things at this level.

Can you elaborate on that? I've tried to find research or demos where people are doing 100+Gbps of useful work in software and haven't seen it. Power 9 will be here soon hopefully, and there's promise, but that doesn't seem like a given.

See drewg's comment. He is being modest in that they are also doing CPU encryption at 100G, so every single stream is different which doubles the usage of memory bandwidth.

I will get to 100G with Skylake, mainly because we have to rework our storage BoM rather than CPU improvements. Intel's focus has been off, they've somewhat misread where the market was going, but even today you have 40 PCIe 3.0 lanes (39GB/s), 67GB/s DDR4 memory bandwidth, and typically more than enough cores and threads to do whatever you want in a single E5 Xeon socket. Computers are _really_ fast, software is slow :)

So right out the gate, you have plenty of speeds and feeds to get stuff off disk and out the wire. That's exactly my workload, which entails pulling data off storage, into the VFS while kqueue is managing a pool of connected sockets, and when they are ready for more data, it goes out right from the page cache with sendfile. Netflix contributed some amazing work that makes FreeBSD particularly optimized for this workload.

In general the trick is to do less, batch more, and try not to copy things around. For example DPDK or Netmap packet forwarding, clear an entire soft ring at a time instead of one packet at a time. Using netmap, you can change ownership of the data by pointer swapping to move it from the rx ring to tx. The ACM Queue article on netmap is particularly good reading. Basically, pass by reference, but by understanding the memory layout of the system.

aio and sendfile kind of suck on Linux. epoll kind of sucks. Linux hugepages really suck, and the Linux VM seems to be biased toward massive concurrency or something that I don't really understand. None of these are monumental technical problems, but there is malignant culture at these hyperscalers because just being a bandwagon fan doesn't make you a winning team. Linux users tend to trust manufacturers to do all the device driver development correctly, and vendors like RedHat to drive general forward progress. How many patches does Amazon have in Xen? Linux?

At the BSD companies I've mentioned, a few dozen people across all of them have pulled this stuff off, and it's all there in the base system. We rip apart vendor drivers or entire subsystems when that's the prescription. We're pretty happy to share details and help others succeed at conferences or even by partnering up team to team across companies.

Thanks for your response. I'm very familiar with DPDK and am looking forward to the changes Skylake brings as well.

RDMA can be rather challenging for a cloud provider, as it typically requires a lossless fabric. Cloud providers don't want to enable flow control on switches (to prevent packet drops) as that has the potential to deadlock the entire network if a buggy or malicious VM stops consuming traffic.

Heck, I took our corp. net down a decade back by causing a test machine to drop into a kernel debugger with flow control enabled on the switches and the test machine. All of a sudden, my remote access to the serial console kernel debugger froze, and I was cursing the flaky VPN. Then a second later, I had the 'Oh Crap, that was me!' realization.

Flow-control as in ECN or Ethernet/pause?

Loss is inevitable in most cloud network fabrics due to the use of shallow buffer commodity ASICs, the amount of fan-in, and the reliance on tenants to use the network in a typical manner (don't fragment, don't encap, preserve entropy).

RDMA is going to be tough - microseconds count, you can't wait for TCP to retrans, and UDP doesn't provide the reliability needed. A new transport protocol is likely the answer.

RDMA has been around for years though. It's big in the HPC world Oracle Rac had used it for some time. In Solaris 11, the default transport for NFS uses RDMA:

https://docs.oracle.com/cd/E23824_01/html/821-1454/rfsrefer-...

Infiniband RDMA is quite old yes but the Ethernet protocols are still rather new and they (iWarp & RoCE) are still competing for supremacy which doesn't really help adoption. At this point it looks like RoCE will win because Intel dropped iWarp but at this point there is basically only one major manufacturer backing each protocol.

Oh I misunderstood the context, yes my examples were in the context of Infiniband cards, thanks. I admit I haven't kept up with RoCE/iWarp. If you have an links to share I would appreciate it. Cheers.

Note that DPDK works just fine with virtio-net on GCE as well, although we have not declared official support for it.

In terms of RDMA and bypass messaging, I agree there can be substantial advantages to offloading transport layer message processing from VMs. Regrettably, I can't say anything more on the subject today.

(I lead the team that owns the virtual NICs exposed to guests in GCE)

Do you not use SR-IOV for GCE?

We do not, although in practice as a guest you wouldn't necessarily know one way or another.

Speaking from (decently informed) personal opinion here--

I see SR-IOV as a means to achieving certain networking characteristics, but one that historically didn't play particularly nicely with live migration (among other things), and one that locks you into particular silicon vendors, etc. It's a bit unfortunate that SR-IOV is often assumed as a prerequisite for high throughput, low latency, low jitter networking. On its own it doesn't guarantee any of those things (you're still beholden to the VCPU scheduler, if nothing else, and there's a lot of 'else'), and it's also not the only way to achieve those things. In particular there are a lot of ways to dedicate hardware to I/O service they aren't SR-IOV

What alternatives would you recommend to people leaning toward SR-IOV?

I say this abstractly as I'm curious what your answer is and I think it might be very helpful to others considering your experience. (I just had to google "sr-iov" as I was typing this :) )

In open source vhost is a pretty good option that abstracts hardware away from VMs and generally performs well.

That said, SR-IOV isn't a BAD option if you don't care about live migration of VMs over a lifespan potentially longer than the underlying hardware platform. It's a good option if you can live with host-hardware-specific drivers in your guests, you're willing to standardize on a specific NIC as host hardware for the fleet where you'll be running VMs, and you're willing to deal with the resource commitment it requires to deliver on its performance promises.

Are you saying that all vendors provide sriov sightly differently in an incompatible way? Because as far as I know, all the vendors have supported it for quite a while (Intel, mellanox, chelsio).

It's not that their SR-IOV implementations are incompatible, it's more that SR-IOV doesn't imply anything about driver compatibility. It's is a mechanism for exposing underlying hardware (or slices of hardware) to guests and nothing more. It does not encompass register sets, queue formats, etc.

So you can assign a virtual function from any SR-IOV-capable NIC into a VM using common code, but what the guest sees inside the VM will still be an Intel, Mellanox, Chelsio, etc. device. Naturally they'll need a driver for that device.

If your fleet includes NICs from a variety of vendors, you'd never be able to live migrate VMs between hosts with different NIC models. Until recently, no vendor I knew of included the relevant serialization and deserialization functionality to allow for live migration at all.

Good point. I didn't think of the driver incompatibility between vendors.

If you are trying to solve multitenancy, SmartOS makes this a non-issue by securely virtualizing Linux syscalls instead of virtualizing an entire computer like VMs.

One way you could tell is lower performance, right? Intel publishes do dpdk benchmarks, and virtio is consistently worse.

Here's what I mean:

http://fast.dpdk.org/doc/perf/DPDK_17_02_Intel_virtio_perfor... http://fast.dpdk.org/doc/perf/DPDK_17_02_Intel_NIC_performan...

Sriov can do almost equivalent to the pmd,I believe.

Unfortunately it's a bit more complicated than that, which is why I hate that SR-IOV gets so tied up in this :/

When they say "virtio-net" there they mean virtio-net inside qemu with vhost servicing the queues on the host side (note, we don't use vhost in GCE -- our device models live in a proprietary hypervisor that's designed to play nicely with Google's production infrastructure). One could just as easily expose what looked like an Intel VF to the guest and service it in the same manner (although there are good reasons not to).

One could also build a physical NIC that exposed virtual functions offering register layouts equivalent to VIRTIOs PCI BARs and used the VIRTIO queue format. If you assigned those into a guest, you'd be doing SR-IOV, but with a virtio-net NIC as seen by the guest. It also likely wouldn't perform as well as a software implementation (in its current form VIRTIO has a lot of serializing dependent loads which make it inefficient to implement over PCIe). There's some ongoing work upstream aimed at a more efficient queue format.

So, yeah, "it depends" is about the best you can do. SR-IOV really just says you're taking advantage of some features of PCI that allow differentiated address spaces in the IOMMU for a single device and (on modern CPUs) interrupt routing to actively running VCPUs without requiring a hop through the host kernel. The former is handy if you want the NIC to be able to cheaply use guest physical addresses (although the IOMMU isn't free either); the latter doesn't matter if the guest is running a poll-mode driver that masks interrupts, nor does it matter if the target VCPU isn't actively running.

Thanks. I look forward to trying it on gce, but as others said, it would be nice if it was officially supported.

Agreed. As a policy, we don't sign off on supporting things until we feel we have sufficient regression testing for them in our automated qual matrix. DPDK is not there yet.

> I can't say anything more on the subject today.

Cool. When should people start poking around GCE's network blog for Interesting Updates™ then?

(Keeping in mind that I acknowledge/note that the "6 months from now" or "next year" or whatever that you say is the date you think we should start keeping an eye out, not necessarily the point in time anything will happen.)

All good points, but keep in mind the 200gbps is somewhat of a gimmick since pcie3 will top out at 128gbps. It's useful for a redundant port, but you won't be pushing 200gbps for a while.

Apparently they have PCIe4 x16 and PCIe3 x32 models. Not sure if either of these exist at the moment but they so satisfy the PCIe bandwidth constraints.

They have one that is two PCIe3 x16 connections from one ASIC right now, it uses a ribbon cable :). That's janky, but it does work on currently available platforms. I've heard Mellanox will do a CAPI NIC, which is quite tantalizing.

Thanks, I didn't see that. But yes, that's weird. In regards to pcie4,I believe the power9 will be the first to have it, but I haven't seen a solid release date for that. Naples didn't look like it had it -- just more pcie3 lanes.