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Memory access on the Apple M1 processor

lemire.me

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Re: Memory access on the Apple M1 processor

#141

Post by FabHK »

namibj wrote: post #110
FabHK wrote: post #98

Earlier quoted context omitted.

FWIW, I ran it on a MacBook Pro (13-inch, 2019, Four Thunderbolt 3 ports), 2.4 GHz Quad-Core Intel Core i5, 8 GB 2133 MHz LPDDR3: two : 49.6 ns (x 5.5) two+ : 64.8 ns (x 5.2) three: 72.8 ns (x 5.6) EDIT to add: above was just `cc`. Below is with `cc -O3 -Wall`, as in Lemire's article: two : 62.8 ns (x 7.1) two+ : 69.2 ns (x 5.5) three: 95.3 ns (x 7.3)

You _need_ to use -mnative because it otherwise retains backwards compatibility to older x86.

  (base) Coding % cc -mnative two-three.c
  clang: error: unknown argument: '-mnative'

  (base) Coding % cc -v
  Apple clang version 12.0.0 (clang-1200.0.32.28)
  Target: x86_64-apple-darwin20.2.0
  Thread model: posix

Re: Memory access on the Apple M1 processor

#142

Post by FabHK »

africanboy wrote: post #132
FabHK wrote: post #98

Earlier quoted context omitted.

FWIW, I ran it on a MacBook Pro (13-inch, 2019, Four Thunderbolt 3 ports), 2.4 GHz Quad-Core Intel Core i5, 8 GB 2133 MHz LPDDR3: two : 49.6 ns (x 5.5) two+ : 64.8 ns (x 5.2) three: 72.8 ns (x 5.6) EDIT to add: above was just `cc`. Below is with `cc -O3 -Wall`, as in Lemire's article: two : 62.8 ns (x 7.1) two+ : 69.2 ns (x 5.5) three: 95.3 ns (x 7.3)

there must be something wrong there, on my late 2014 laptop that mounts Type: DDR4 Speed: 2133 MT/s I get two : 27.1 ns (3x) two+ : 28.6 ns (2.2x) three: 39.7 ns (3x) which is not much, considering this is an almost 6 years old system with 2x slower memor

Dunno, I didn't reboot and didn't close all other programs (browser, editor, mail, calendar, notes, editor)... Top shows

Load Avg: 2.36, 2.01, 1.97 CPU usage: 2.10% user, 3.39% sys, 94.49% idle

Re: Memory access on the Apple M1 processor

#143

Post by proverbialbunny »

jandrese wrote: post #101
pdpi wrote: post #20

Earlier quoted context omitted.

This seems to be a recurring theme with the M1, and one that, in a sense, actually baffles me even more than the alternative. There is no "magic" at play here, it's just lots and lots of raw muscle. They just seem to have a freakishly successful strategy for choosing what aspects of the processor to throw that muscle at. Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What en…

It seems like Apple listened when people talked about how all modern processors bottleneck on memory access and decided to focus heavily on getting those numbers better. Of course this leads to the question that if everyone in the industry knew this was the issue why weren't Intel and AMD pushing harder on it? They already both moved the memory controller onboard so they had the opportunity to aggressively optimize i…

My guess is it had to do with limitations tied to the x86_64 instruction set. It doesn't matter how much modifications you do, if you don't start with a good foundation, you're going to be limited to that foundation.

Re: Memory access on the Apple M1 processor

#144

Post by ogre_codes »

jeffbee wrote: post #114
coldtea wrote: post #91

Earlier quoted context omitted.

> Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What enabled/led them to make those choices where others haven't? The things people give them complains about: (a) keeping a walled garden, (b) moving fast and taking the platform to new directions all at once (c) controlling the whole stack Which means they're not beholden to compatibility with third party frameworks and big…

Neither A nor C makes any sense, are not supported by evidence. There is no aspect of the mac or macOS that can be realistically described as a "walled garden". It comes with a compiler toolchain and ... well, some docs. It natively runs software compiled for a foreign architecture. You can do whatever you want with it. It's pretty open. A "walled garden" is when there is a single source of software.

People seem to get creative about terminology. It's not remotely like what I'd consider a walled garden (xBox, iOS, Playstation, etc).

Re: Memory access on the Apple M1 processor

#145

Post by proverbialbunny »

martamorena2 wrote: post #135
jeffbee wrote: post #79

Earlier quoted context omitted.

I don't have any inside-Apple perspective, but my guess is having a tight feedback cycle between the profiles of their own software and the abilities of their own hardware has helped them greatly. The reason I think so is when I was at Google is was 7 years between when we told Intel what could be helpful, and when they shipped hardware with the feature. Also, when AMD first shipped the EPYC "Naples" it was crippled…

That's bizarre. As if CPU vendors were unable to run "realistic" workloads. If they truly aren't, that's because they are unwilling and then they are designing for failure and Apple can just eat their lunch.

As a data scientist, I feel this. Intel and AMD don't own an OS or an app store, and you might be surprised how hard it is to get good data. Data is the new gold. If a company that can corner a piece of the market, they can collect data no one else can, and from that companies are often forced to partner or they can't properly provide services that will keep them competitive.

Re: Memory access on the Apple M1 processor

#146

Post by coldtea »

jeffbee wrote: post #114
coldtea wrote: post #91

Earlier quoted context omitted.

> Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What enabled/led them to make those choices where others haven't? The things people give them complains about: (a) keeping a walled garden, (b) moving fast and taking the platform to new directions all at once (c) controlling the whole stack Which means they're not beholden to compatibility with third party frameworks and big…

Neither A nor C makes any sense, are not supported by evidence. There is no aspect of the mac or macOS that can be realistically described as a "walled garden". It comes with a compiler toolchain and ... well, some docs. It natively runs software compiled for a foreign architecture. You can do whatever you want with it. It's pretty open. A "walled garden" is when there is a single source of software.

Walled garden has many meanings, depending on context.

macOS promotes the App Store as the source of software (even if it's not the sole), and has walls like notarization requirements and the Gatekeeper to prevent weeds from intruding.

With the App Store Apple knew that there's a pool of N apps that follows its guidelines, has passed internal checks for API use, and can be converted quite easily to a different architecture, that it could count on.

Their control over the platform allowed them to enforce Metal and deprecate OpenGL pronto, to add a new combined iOS/macOS UI libs, to introduce Marzipan.

They have also added stuff like Universal Binary support, and most importantly Bitcode, which abstracts away parts of the underlying architecture.

All of those where steps towards the ARM/M1 (and future developments), and all were enabled via Apple's control of the hardward, software, and - sure, partial - control of third party apps.

Re: Memory access on the Apple M1 processor

#147

Post by coldtea »

fartcannon wrote: post #92
coldtea wrote: post #91

Earlier quoted context omitted.

> Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What enabled/led them to make those choices where others haven't? The things people give them complains about: (a) keeping a walled garden, (b) moving fast and taking the platform to new directions all at once (c) controlling the whole stack Which means they're not beholden to compatibility with third party frameworks and big…

They could still do all this shit without the walled garden. To me, it suggests they aren't willing to compete. They're anti-competitive.

>They could still do all this shit without the walled garden

With much slower adoption, pushback, and bike-shedding, like in the Microsoft and Linux world.

>To me, it suggests they aren't willing to compete.

Compete with what? With themselves? They compete with Windows (and to a degree Linux, though few care for that), and with Android. They'd compete with Windows Phone too if MS wasn't incompetent.

But they didn't do anything to preclude others from making their OS/hardware and selling it to customers. In fact, they have nowhere near a monopoly in either the desktop (10% or less) or the mobile space (40% or less).

Whereas MS for example, had 98% of the desktop (home and enterprise), and abused its power to threaten OEMs to do its bidding against Linux etc.

Re: Memory access on the Apple M1 processor

#148

Post by ogre_codes »

fartcannon wrote: post #92
coldtea wrote: post #91

Earlier quoted context omitted.

> Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What enabled/led them to make those choices where others haven't? The things people give them complains about: (a) keeping a walled garden, (b) moving fast and taking the platform to new directions all at once (c) controlling the whole stack Which means they're not beholden to compatibility with third party frameworks and big…

They could still do all this shit without the walled garden. To me, it suggests they aren't willing to compete. They're anti-competitive.

> They could still do all this shit without the walled garden.

They do. MacOS isn't a walled garden.

> They're anti-competitive

Have you heard of this little company from Washington called Microsoft? They have something like 85% of the PC market. There is another OS called Linux. About 85-90% of the internet runs on it.

I can understand a little where people get the idea the iPhone is anti-competitive, but we're talking about MacOS here.

Re: Memory access on the Apple M1 processor

#150

Post by alecco »

titzer wrote: post #123
jeffbee wrote: post #2

Great practical information. Nice to see people who know what they are talking about putting data out there. I hope eventually these persistent HN memes about M1 memory will die: that it's "on-die" (it's not), that it's the only CPU using LPDDR4X-4267 (it's not), or that it's faster because the memory is 2mm closer to the CPU (not that either). It's faster because it has more microarchitectural resources. It can load…

Frankly, I find Lemire does oversimplified, poor-quality control, back-of-the-envelope microbenchmarking all the time that provides little to no insight other than establishing a general trend. It's sophomoric and a poor demonstration about how to well-controlled benchmarking that might yield useful, repeatable, and transferrable results.

Can you give an example? I've seen Lemire correct his posts on many occasions and the source code is published. I don't know many blogs doing anything remotely like that.
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