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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

#121

Post by girvo »

horsawlarway wrote: post #73
chubot wrote: post #60

Earlier quoted context omitted.

What item #3 tells you is that any performance gains in the last decade and a half you've experienced have been driven by multi-core, not faster processors. And that means Amdahl's Law is more important than Moore's Law these days. Uh or storage and networking? Not sure why you would leave that out, since they're the bottleneck in many programs. The slowest things are the first things you should optimize

Yeah... SSDs are so much faster than spinning disk it's not even funny. I literally refuse to run a machine that boots its main OS from spinning disk anymore. The 60 bucks to throw an SSD into it is so incredibly cheap for what you get. My wife's work gave her a (fairly basic but still fine) thinkpad - except they left the main drive as a fucking 5400rpm hdd. Then acted like assclowns when we repeatedly showed them t…

Lusting after those 10k VelociRaptor drives back in high school... man I have a funny amount of nostalgia for, in hindsight, pretty average hardware once the world moved forward!

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

#122

Post by opportune »

efuquen wrote: post #78
TillE wrote: post #56

Earlier quoted context omitted.

It's pretty remarkable that, for efficient data processing, it's super super important to care about memory layout / cache locality in intimate detail, and this will probably be true until something fundamental changes about our computing model. Yet somehow this is fairly obscure knowledge unless you're into serious game programming or a similar field.

> Yet somehow this is fairly obscure knowledge unless you're into serious game programming or a similar field. Because the impact in optimizing hardware like that can be not so important in many applications. Getting the absolute most out of your hardware is very clearly important in game programming, but web apps where scale being served is not huge (vast majority)? Not so much. And in this context developer time is…

IMO we are only scratching the surface of cloud gaming so far. Right now it’s pretty much exclusively lift-and-shift, hosted versions of the same game, in many cases running on consumer GPUs. Cloud gaming allows for the development of cloud-native games that are so resource intensive (potentially architected so that more game state is shared across users) that they would not possible to implement on consumer hardware. They could also use new types of GPUs that are designed for more multi tenant use cases. We could even see ASICS developed for individual games!

I think the biggest challenge is that designing these new types of games is going to be extremely hard. Very few people are actually able to design performance intensive applications from the ground up outside of well-scoped paradigms (at least web servers, databases, and desktop games have a lot of prior art and existing tools). Cloud native games have almost no prior art and almost limitless possibilities for how they could be designed and implemented, including as I mentioned even novel hardware.

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

#123

Post by Gigachad »

themacguffinman wrote: post #103
Gigachad wrote: post #88

Earlier quoted context omitted.

TBH I don't think cloud gaming is a long term solution. It might be a medium term solution for people with cheap laptops but eventually the chip in cheap laptops will be able to produce photo realistic graphics and there will be no point going any further than that

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 sufficient and the average user would never buy an actual sound card or usb dac. Even though the dedicated one is better, it isn’t that much better.

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

#124

Post by fouc »

dgl wrote: post #90
jandrese wrote: post #31

The "commodity network" thing is kind of weird. I'd expect that to make a 10x jump when switches went from Fast Ethernet to Gigabit (mid-late 2000s?) and then nothing. I certainly don't feel like they've been smoothly increasing in speed year after year. I'm also curious about those slow 1990s SSDs.

I was curious too, the network one is a TODO: https://github.com/colin-scott/interactive_latencies/blob/ma... Although I'd expect more jumps than Fast Ethernet to Gigabit, it's true the consumer space is kind of stuck on Gigabit (with 2.5 GbE just becoming more common now). Datacenters have had at least 10 GbE for many years.

It seems to be entirely based on NIC bandwidth, rather than the actual time it takes for information to travel between servers via ethernet or optics within a LAN.

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

#125

Post by opportune »

Gigachad wrote: post #88
efuquen wrote: post #78

Earlier quoted context omitted.

> Yet somehow this is fairly obscure knowledge unless you're into serious game programming or a similar field. Because the impact in optimizing hardware like that can be not so important in many applications. Getting the absolute most out of your hardware is very clearly important in game programming, but web apps where scale being served is not huge (vast majority)? Not so much. And in this context developer time is…

TBH I don't think cloud gaming is a long term solution. It might be a medium term solution for people with cheap laptops but eventually the chip in cheap laptops will be able to produce photo realistic graphics and there will be no point going any further than that

Cloud gaming allows for more shared state and computationally intensive games (beyond just graphics). Maybe eventually clients will easily be able to render 4k with tons of shaders but the state they’re rendering could still be computed remotely. In a way that’s kind of what multiplayer games are like already

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

#126

Post by lucb1e »

If it was an hour earlier I'd save everyone time with a graph instead of trying to get an idea by eyeballing blocks while playing with a slider, but alas it's 1:09am and I really should sleep. I think a simple multi-line plot/graph made using a simple spreadsheet or whatever would be a lot more useful than having to keep in mind different values and moving time forwards manually, so if anyone else feels encouraged...

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

#128

Post by ip26 »

greggsy wrote: post #39
gameswithgo wrote: post #25

An instructive thing here is that a lot of stuff has not improved since ~2004 or so, and working around those things that have not improved (memory latency from ram all the way down to l1 cache really) requires fine control of memory layout and minimizing cache pollution, which is difficult to do with all of our popular garbage collected languages, even harder with languages that don't offer memory layout controls, a…

It’s interesting that L2 cache has basically been steady at 2MB/core since 2004 aswell. It hasn’t changed speed in that time, but is still an order of magnitude faster than memory across that whole timeframe. Does this suggest that the memory speed bottleneck means that there simply hasn’t been a need to increase availability of that faster cache?

Every level of cache strikes a balance between latency & capacity. Bigger caches have higher latency; it's a fundamental property of caches.

What you can conclude is that 0.5MB-2MB and 12-15 cycles of latency has been a steady sweet spot for L2 size for twenty years.

Sidebar: it was a property of caches. 3D assembly may upend the local optima.

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

#130

Post by ip26 »

TillE wrote: post #56
gameswithgo wrote: post #25

An instructive thing here is that a lot of stuff has not improved since ~2004 or so, and working around those things that have not improved (memory latency from ram all the way down to l1 cache really) requires fine control of memory layout and minimizing cache pollution, which is difficult to do with all of our popular garbage collected languages, even harder with languages that don't offer memory layout controls, a…

It's pretty remarkable that, for efficient data processing, it's super super important to care about memory layout / cache locality in intimate detail, and this will probably be true until something fundamental changes about our computing model. Yet somehow this is fairly obscure knowledge unless you're into serious game programming or a similar field.

The logical conclusion is that most fields have so much data processing capacity relative to the problem size, they don't need to worry about efficient data processing.
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