[HN Gopher] Transatlantic ping faster than sending a pixel to th...
___________________________________________________________________
Transatlantic ping faster than sending a pixel to the screen?
(2012)
Author : notRobot
Score : 91 points
Date : 2021-11-25 13:03 UTC (9 hours ago)
(HTM) web link (superuser.com)
(TXT) w3m dump (superuser.com)
| Veliladon wrote:
| The transatlantic ping is waves traveling at the speed of light
| in fiber and a large fraction of the speed of light in copper. To
| send a pixel to a screen you need to wait for the next vsync if
| you're not using a variable refresh rate display. That alone can
| be double digit milliseconds. Then you need to wait for the
| crystals in the screen to physically move in response to applied
| voltage. Moving things is slow. Moving things happens at speeds
| far less than the speed of light unless you're putting in enough
| energy to vaporize a city.
|
| If you wait around and rely on things that move extremely slowly
| compared to the light speed of fiber and near light speed of
| electrical signals, waiting around for a crystal to turn and
| align itself to a voltage is going to take an eternity in
| comparison.
|
| So yeah, no shit it's slower to display a pixel.
| cozzyd wrote:
| Well the effective refractive index of fiber is something like
| 1.4 or so I think.
| marginalia_nu wrote:
| That's only half the story. If you compare a PAL NES game,
| which runs at a fixed 50 FPS, to a modern video game that runs
| at 50 FPS, the former is incredibly snappy whereas the latter
| would be deemed unplayable sluggish. The NES signal is analog
| and if you update the video memory, it more than likely shows
| up on the screen the next frame, the worst possible delay is 20
| milliseconds.
|
| Digital displays and (hardware) pipeline-based rendering means
| that it in practice often takes takes several frames between
| sending the instructions to draw mario and the little guy
| showing up on the screen. It still takes less than 20
| milliseconds to render, but the latency is much higher. In
| practice a latency of 100 ms isn't unheard of at 50 FPS with a
| modern rendering pipeline. This is why modern games feel so
| sluggish at low framerates.
| mdoms wrote:
| Perhaps you should read the linked Q&A before commenting.
| klmr wrote:
| I dunno, I don't think it's _that_ obvious: the physical
| movement in an LCD is across tiny masses and distances (at
| molecular scale); the network signal has to cross a distance
| that's _many orders of magnitude_ larger. Comparing these two
| things without looking at actual number doesn't strike me as
| valid, even for approximations.
|
| Furthermore, if I'm reading the RTINGS.com source posted below
| correctly, modern LCDs have _smaller_ latencies than a
| transatlantic ping. So not only is it not obvious, it's no
| longer universally true.
| breakingcups wrote:
| Note that John Carmack himself provided that answer.
| ChrisArchitect wrote:
| anything new on this?
|
| previous discussion from _10 years ago_ :
| https://news.ycombinator.com/item?id=3914638
| clktmr wrote:
| Optimizing for latency is often counter-intuitive.
|
| Polling as an example may be an effective way to lower latency,
| e.g. Linux NAPI.
|
| Increasing buffer sizes may also decrease latency because data
| can be processed in bursts, see buffer starvation. But if data
| comes in at a higher rate than can be processed, buffers fill up
| and are horrible for latency.
| SV_BubbleTime wrote:
| > Polling as an example may be an effective way to lower
| latency,
|
| I had to learn this lesson the hard way recently.
|
| An embedded system where I had to get data from a couple SPI
| controller's RAM. Made a bit complicated ISR and listener
| system that woke up threads to do a deferred-interrupt... by
| the time it was all said and done with a fair bit of code, I
| wasn't happy with it.
|
| I figured out that usually data would be available every 2ms
| and just wrote the read routine just to sleep every 2ms and
| attempt another read, I have it "hitting" 90% of the time and
| my avg latency is almost nothing. .7ms or so.
| ksec wrote:
| I have always been crying about latency computing for years. My
| earliest HN comment on the topic was in 2012. And I have been
| ranting about it for even longer outside
|
| I really hope at the later part of this decade we start focusing
| on latency computing instead of bandwidth. From Display, Input,
| Output and Network, and down to OS and Software. I had always
| hoped VR would forced those optimisation due to VR being a
| latency sensitive, as John Carmack was doing at the time. But VR
| never happened.
| hhhhhklkkliiii wrote:
| VR never happened? Someone needs to let Valve and Oculus know..
| emteycz wrote:
| Well it certainly did not happen in way other technologies
| happened - smartphones, social networks, laptops, desktops...
| VR is definitely slower and smaller market right now than
| these other devices were after similar number of years.
| SV_BubbleTime wrote:
| I'm ok with VR being slow. There is no need to rush it.
| There are some amazing VR experiences. Half Life Alyx while
| standing, despite it being a disaster overall VirtaMate can
| have some really interesting erotic setups, beat saber is
| the only music game I've ever really got into, and... IDK,
| some things are just not possible outside of VR like
| SuperHot VR being a totally different everything than it's
| normal version.
|
| I would like there to be more quality content but sooner,
| but I think it's largely in a grey area between hardware
| not being good enough yet and software being expensive to
| develop.
|
| I used to poopoo it, but I've come around that VR is in the
| cards, just slowly.
| retrac wrote:
| To me, the threshold of cringing is when web forms are laggy.
| This 50-billion-instructions-per-second box can be slower
| rendering an input form than a VT220 terminal from 1983. When
| the task of the machine is to, e.g. enter appointment booking
| information, and it handles the task worse than hardware from
| decades ago could in some cases, that's when we know we've lost
| the plot.
| cozzyd wrote:
| Yes, or, even more annoyingly, when slack lags as you type. I
| think I've had ssh connections to the south pole with less
| latency than slack sometimes has.
| Aerroon wrote:
| A big performance problem is live autocomplete on your input.
| The website running some kind of a query on every character
| you input sometimes causes huge delays. On my phone I can
| sometimes wait a good 5-10 seconds after I finished typing
| for it to actually show up on screen.
| ksec wrote:
| >To me, the threshold of cringing is when web forms are
| laggy.
|
| Same here that was what ticked me. I was reading up HN
| threads I saved and the Remix framework was one of them.
| People were cheering for a well design, animated and smooth
| _webpage_. Because most of the other similar design tends to
| Jank and not smooth. We are coming to 2022, rendering a
| webpage on modern CPU with GPU accelerated browser should be
| trivial. And yet that web page was, true to most comments and
| my experience, an outliner.
|
| A lot of people continue to say those latency doesn't matter.
| It does. I am picky, I hate latency. I am latency sensitive.
| I can only wish some day ( again may be VR or Metaverse ) we
| could kick start latency computing. Or Real Time computing.
|
| "To make Metaverse, we need Real Time Computing" seems like a
| good message to VC and consumer market :)
| stygiansonic wrote:
| RTINGS.com has a decent database of displays sorted by input lag
| (which is the topic of this post):
| https://www.rtings.com/monitor/tests/inputs/input-lag
| adolph wrote:
| This is a classic and wonderful way to learn and think about the
| junction of physics and computers.
|
| Another one is https://news.ycombinator.com/item?id=702713
| OJFord wrote:
| Gosh that's a fun read in all sorts of ways. SSDs are
| relatively new, there are hold-outs, and they cost $300 for
| 80GB!
| walrus01 wrote:
| At right around the time that was published in 2009, I bought
| a new 17 inch MacBook pro and a $350 Intel 80GB 2.5" SATA
| ssd, and stuck the SSD into the position formerly occupied by
| the dvdrw in a special holder. Worked great as boot drive.
| anthropodie wrote:
| Imgur has has become so horrible that it loaded all
| recommendations first and it had still not loaded the main
| content before I closed the tab. I wish this was hosted
| somewhere else.
| tyingq wrote:
| Never loaded for me. Alternate site: https://ibb.co/HHgRSG8
| marcosdumay wrote:
| That image would be better by having an year tag.
|
| Since then the ratios increased (L1 to RAM by quite a bit), SSD
| became common, and networks got intermingled with everything.
| usr1106 wrote:
| Or having a series of images every 5-10 years. Or have
| factors changed so little that not much additional would be
| shown?
| walrus01 wrote:
| This is one of the reasons why the hardcore retro gaming people
| are still paying big money for 32" Sony Trinitron analog CRT TVs
| and such. Ultra low latency from image source to display.
|
| If you have a good condition Trinitron like display these days
| (Mitsubishi diamondtron, sony pvm, etc) it is presently
| appreciating in value every year.
___________________________________________________________________
(page generated 2021-11-25 23:02 UTC)