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Open-sourcing a more precise time appliance

engineering.fb.com

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Re: Open-sourcing a more precise time appliance

#171

Post by williamscales »

bohemian99 wrote: post #15
kd913 wrote: post #11

Earlier quoted context omitted.

That seems rather ambiguous and doesn't really explain why having more time precision results in faster performance or 'advanced infrastructure management'. I can understand why a stock broker or trading firm requires PTP to enable precise date-stamps for auditing/validating trades. I don't see how having a time granularity on the order of picoseconds is needed for a data center.

In distributed databases that offer transaction semantics, they need timestamps to order transactions that take place. A tighter synchronization of clocks mean they can execute transactions faster because they can reduce the amount of time they wait (based on the potential clock drift between machines in the data center)

Wouldn’t it be better to put the effort towards designing a system that doesn’t need precise timekeeping?

Re: Open-sourcing a more precise time appliance

#172

Post by tourist2d »

eplanit wrote: post #68
toomuchtodo wrote: post #67

Earlier quoted context omitted.

I am torn. I absolutely love the technical blog post and the effort that went into open sourcing everything needed to build these devices, but, you know, Facebook. Compliments and respect to the engineers involved for really well done engineering.

They've built and earned their (negative) reputation. This is cool, but it's like Philip Morris Tobacco Company coming out with a useful home appliance. Uhh....thanks?

Except it's a software company releasing an open source software project?

Re: Open-sourcing a more precise time appliance

#173

Post by anon_tor_12345 »

LeifCarrotson wrote: post #170
anon_tor_12345 wrote: post #155

Earlier quoted context omitted.

you don't need vivado to modify the hdl, you need vivado (or some other proprietary xilinx toolchain) to produce the bitstream which actually deploys to the fpga.

That's a level of nitpicking that I didn't bother with. Of course the Verilog or VHDL is just plaintext, which you can modify anywhere, but to actually do anything with it you need to compile it into a bitstream. It does make me wonder if someone could set up a CI server to get around proprietary compilers like Vivado. Point the community resource at your source and get back a binary! Obviously you'd need to strip th…

i didn't mean to nitpick and it's not nitpicky since there are now open toolchains (though not for xilinx) that you support verilog as a frontend

http://www.clifford.at/yosys/ http://www.clifford.at/icestorm/

Re: Open-sourcing a more precise time appliance

#175

Post by Animats »

How resistant is this to a GPS attack? It has an atomic clock, so it should be producing good data for days while sending alarms in the event the GPS data is bogus. You don't want to create a situation where someone aims a small dish at the roof of your data center and takes down the networking.

Re: Open-sourcing a more precise time appliance

#176

Post by abyagowi »

Animats wrote: post #175

How resistant is this to a GPS attack? It has an atomic clock, so it should be producing good data for days while sending alarms in the event the GPS data is bogus. You don't want to create a situation where someone aims a small dish at the roof of your data center and takes down the networking.

I have been working on a version with two GNSS receivers L1/L2 and L1/L5. The SA53 receives two PPS inputs and that allows you to detect Spoofing and Jamming. Again, I like to emphasize, this is not a done work. We shared whatever we had and we would love to have the community to contribute and help making it better. I love to have as many applications as possible for this Time Card. For example, I am looking for someone willing to port/write a Windows driver for the time card. With regards to the VHDL code; we are working with NetTimeLogic on a version without the need of any of theirs proprietary IPs. Meanwhile, we provided you with whatever we have and we look forward to working with you. Please feel free reach out to me if you like to collaborate on this project.

Re: Open-sourcing a more precise time appliance

#177

Post by abyagowi »

myself248 wrote: post #98
abyagowi wrote: post #47

Earlier quoted context omitted.

Of course we are not going to build the card in the lab with assembling SMD parts. This was more a way to explain that building such a card should not be out of access for anyone

I mean, you can buy a syringe of solder paste for thirty bucks and do the reflow in a toaster oven. Anyone not doing it simply isn't trying.

You are right. This sentence was not supposed to be a literal description of what is the best way to build the card. It was more referring to the fact the building this card is not that hard since the main goal for this project was to liberate the time appliances from being a closed source box.

Re: Open-sourcing a more precise time appliance

#178

Post by traceroute66 »

Am I missing something? The FB blog proudly states how they improved accuracy "10 milliseconds to 100 microseconds".

Surely that's a lot of effort that anybody with in a datacentres with decent connectivity could replicate with a Chrony instance ?

100 microseconds is 0.0001 seconds, right ?

Seems to be something Chrony can do with its eyes closed:

System time : 0.000003297 seconds slow of NTP time Last offset : +0.000000549 seconds

There are lots of great NTP servers out there hosted by trusted parties such as national time labs. Most people don't need fancy GPS hardware (and the expense of paying someone for roof access to put your antenna !). If you've got good software and good connectivity you can replicate 99.999% of the same thing.

Re: Open-sourcing a more precise time appliance

#179

Post by Bluecobra »

xwolfi wrote: post #96
lordnacho wrote: post #70

Earlier quoted context omitted.

Certain trading operations require it. I think there's even a regulatory under Mifid2, bit I'm not in the know about the legals.

I work in trading, but mostly on the asian markets, so not sure about mifid. Usually the exchanges seem to give milli to second precision (which is very annoying: if Thailand says it's second-precision to timestamp their order executions but Taiwan says it's milli, our system has to use the most precise when ordering them and we get questions from our own multi market clients about why all these executions are seemin…

Not all exchanges are like this. The JPX exchange in Tokyo provides PTP over dedicated cross-connects, and is super accurate, within +/-25ns. It’s pretty neat seeing a PTP clock from Seiko.

Re: Open-sourcing a more precise time appliance

#180

Post by somebody_amzn »

walrus01 wrote: post #148

> the ConnectX-6 Dx network card I would caution people against using the Mellanox/NVIDIA network interface cards in anything they care about. The driver license is proprietary and you have to build it for your kernel as a DKMS module in a semi manual process. Makes future system updates a real bother. I realize this probably doesn't apply so much to FB internally since they build and maintain their own distro in hou…

(disclaimer: am an AWS employee)

Hello,

Where did you get that from? The drivers for NVIDIA networking cards are in the upstream kernel. You have the option of using newer versions from DKMS if the built-in version for your kernel is too old.

You can see the release notes for each version as present on the upstream kernel at https://docs.mellanox.com/display/kernelupstreamv512/Linux+K... for Linux 5.12 for example.

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