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How “latency numbers everybody should know” decreased from 1990–2020

colin-scott.github.io

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Re: How “latency numbers everybody should know” decreased from 1990–2020

#131

Post by CobrastanJorji »

kens wrote: post #27

Amazing performance improvements, except no improvement at all on the packet roundtrip time to Netherlands. Someone should really work on that.

The great circle distance between SF and Amsterdam is about 5,450 miles. A round trip is 10,900 miles. At the speed of light, that's 58.5 milliseconds. So in theory, infinitely efficient computers (and some sort of light-in-a-vacuum wire) and networking equipment could knock 60% off that time, but no more.

However, I suspect one big problem is that there are a number of hops between the Netherlands and San Francisco. I suspect there's not a fiber line that goes right through Idaho to Greenland, then, Scotland, and then the Netherlands. I'm curious what the actual route is be and how many miles are involved.

Re: How “latency numbers everybody should know” decreased from 1990–2020

#132

Post by 0xCMP »

Gigachad wrote: post #123
themacguffinman wrote: post #103

Earlier quoted context omitted.

Photo realistic graphics ought to be enough for anybody? This seems unlikely, there's so many aspects to graphical immersion that there's still plenty of room for improvement and AAA games will find them. Photo realistic graphics is a rather vague target, it depends on what and how much you're rendering. Then you need to consider that demand grows with supply, with eg. stuff like higher resolutions, even higher refre…

There are diminishing returns. If a laptop could play games at the quality of a top end PC today, would people really want to pay for an external streaming service, deal with latency, etc just so they can get the last 1% of graphical improvements? We have seen there are so many aspects of computing where once it’s good enough, it’s good enough. Like how onboard DACs got good enough that even the cheap ones are suffic…

I think what you're missing is that

1) you still need to install and maintain it and there are many trends even professionally that want to avoid that

2) just cause you could get it many may not want it. I could easily see people settle for a nice M1 MBA or M1 iMac and just stream the games if their internet is fine. Heck, wouldn't it be nicer to play some PC games in the living room like you can do with SteamLink?

3) another comment brings a big point that this unlocks a new "type" of game which can be designed in ways that take advantage of more than a single computer's power to do games with massively shared state that couldn't be reliably done before.

I think to counter my own points: 1) I certainly have a beefy desktop anyways 2) streaming graphics are not even close to local graphics (a huge point) 3) there is absolutely zero way they're gonna steam VR games from a DC to an average residential home within 5 years IMHO.

Re: How “latency numbers everybody should know” decreased from 1990–2020

#133

Post by thfuran »

nightpool wrote: post #96
thfuran wrote: post #57

Earlier quoted context omitted.

Which latency are you suggesting is limited by the speed of light?

"Packet roundtrip CA to Netherlands"

No, at the speed of light 150 ms is about long enough to send a packet from SF to Amsterdam and then send the reply back the long way around the entire rest of the planet.

Re: How “latency numbers everybody should know” decreased from 1990–2020

#135

Post by tomxor »

teraflop wrote: post #93
genewitch wrote: post #65

Earlier quoted context omitted.

the radius of the arc in low earth orbit (or whatever) is going to be larger than the arc across the atlantic ocean. As no one has ever said: "I'll take glass over gas, thanks."

Yeah, but the faster speed of light through vacuum can still be enough to make up for the longer path. Back-of-the-envelope calculation: at an altitude of 550km and minimum elevation of 25 degrees above the horizon, a single Starlink hop could cover a maximum of 1880km of distance along the earth's surface, with a ground-satellite-ground length of 2068km. So the total distance traveled through space is about 10% fart…

The 3rd parent was suggesting hollow core fiber, which I _think_ is supposed to reduce the distance travelled to near fiber length through band gap effects i.e eliminating the extra distance travelled in regular fiber core due to total internal reflection, hence the lower latency. Light still travels about 2/3 the speed in silica core compared to in a vacuum, so it would make the fastest possible speed 2*10^8 m/s (per meter of actual fiber)

So in order for LEO satellites to compete, the total distance from A to B must be less than 1.5 times the equivalent of hollow core fiber on the ground.

Oh god I have to do trig! So finding the ratio of the the horizontal (ground) to vertical (altitude) when the hypotenuse is 1.5 * the horizontal =

  (1.5**2-1)**0.5 = 1.118033988749895.
i.e 1:1.11 half-ground:altitude

  550 / 1.118033988749895 * 2 = 984km
i.e A single hop Satellite at 550km altitude would beat a straight line (ignoring curvature, bored through the ground) hollow core fiber at 984km (I _think_ :P). Realistically you can probably lower the distance since we don't actually get straight line A-B fiber, but that's still quite a long minimum distance.

Disclaimer: there are too many assumptions and approximations in here, it's just for fun.

[edit]

whoops, hollow core is supposed to be almost speed of light, so actually it's not much of a competition any more in the idealised case.

Re: How “latency numbers everybody should know” decreased from 1990–2020

#136

Post by favorited »

_pastel wrote: post #40

These numbers focus on reads. How does writing speed to cache, main memory, or disk compare? Anyone have some ballparks to help me build intuition?

Writes are much slower than reads, but modern CPUs have a write-buffer for each core so they don't need to wait for the write to propagate back down the caches and into main memory before continuing execution.

Re: How “latency numbers everybody should know” decreased from 1990–2020

#137

Post by zozbot234 »

capitainenemo wrote: post #119
horsawlarway wrote: post #117

Earlier quoted context omitted.

I mean... at the risk of asking a loaded question - have you tried an ssd? Because, I'm also spoiled on RAM so I don't have to pick, but if I haaad to pick - I'd take a machine with 8gb of RAM and an SSD over 32gb of RAM and an HDD almost any day (actually - literally any day except when I'm running our full service stack at work, which needs about 12gb of RAM to be workable) If I have a bunch of media - sure, throw…

Yep. All the laptops in the house are SSD. I really haven't noticed much of a difference, sorry. Everything is linux too, but I find it hard to believe that would matter. I mean, NTFS is a notoriously slow file system (Hedgewars, Firefox and Minecraft all had to rearchitect to handle its horrendous handling of many small files), but the reasons for it I think would not change that much with SSD. The thing is. How wou…

I agree about this. SSD leads to impressively fast boot/early load times, and it might help if you have to run workloads that stress both RAM and I/O, but other than that it doesn't really matter if you're running a proper OS. And you can put a swap file/partition on a spinning disk without worrying about endurance or having less space for files. So the performance argument goes both ways, and the extra storage space of spinning rust is very convenient.

Re: How “latency numbers everybody should know” decreased from 1990–2020

#138

Post by thundergolfer »

sigstoat wrote: post #64

the code appears to just do a smooth extrapolation from some past value. it claims that (magnetic) disk seek is 2ms these days. since when did we get sub-4ms average seek time drives? it also seems to think we're reading 1.115GiB/s off of drives now. transfer rate on the even the largest drives hasn't exceed 300MiB/s or so, last i looked. ("but sigstoat, nvme drives totally are that fast or faster!" yes, and i assume…

Yes, this is a huge problem with the data for 2012 onwards. See: https://github.com/colin-scott/interactive_latencies/issues/....

Re: How “latency numbers everybody should know” decreased from 1990–2020

#139

Post by thundergolfer »

csours wrote: post #10

It looks like almost everything is blazing fast now. I'm not sure how long the first X takes though - how long does it take to establish a TCP/IP connection? How long does it take an actual program to start reading from disk?

It looks like that because an inaccurate projection from 2012 has been made by the tool. See https://github.com/colin-scott/interactive_latencies/issues/....
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