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I think you got the point most people miss - apple had a unique ability to profile every app on the Mac and iOS App Store, possibly in an automated way, as part

I think you got the point most people miss - apple had a unique ability to profile every app on the Mac and iOS App Store, possibly in an automated way, as part of the app submission pipeline. Intel and AMD could go out and profile real work applications, and I’m sure they do, but to get to the same level of breadth is probably not possible.

pvg 5y ago
Is that really such a unique advantage for Apple? Intel and AMD can work with Microsoft to achieve something similar, for instance.
- bch 5y ago
  I’m only speculating, but I’d think they wouldn’t even “have to work with” anybody - couldn’t they just instrument whatever they want?
  - pvg 5y ago
    Sure, I just meant there's a Microsoft store so if the there was something particularly advantageous to having access to an app store, Intel or AMD are not completely in the wilderness here.
    - zsmi 5y ago
      Not completely in the wilderness sure. But they also have many operating systems to consider. The other obvious ones are Linux, BSD, and, until very recently, macOS. Are you sure it's possible to do a micro-optimization for one without nerfing the others?
      - ygra 5y ago
        Does the actual machine code doing computations really differ that much based on the OS? I'd guess the differences are just that you call different libraries and maybe a different calling convention, but nothing that would impact code running single-threaded without preemptions much.
        zsmi 5y ago
        How the architecture handles the memory hierarchy is hugely important, but your example of calling conventions is a good one too. Keep in mind what calling conversions are: "Calling conventions act as a contract between subroutines at the assembly level." https://levelup.gitconnected.com/x86-calling-conventions-a34812afe097 https://levelup.gitconnected.com/x86-calling-conventions-a34...
- simondotau 5y ago
  It's also worth noting that Apple truly has the whole stack under their roof, including the team that maintains their C compiler and optimises LLVM's ARM machine code output. Intel has their own C compiler too, but one wonders to what extent they can profile real commercial software compiled using it, and feed that profiling knowledge back to the silicon designers in a useful way. The existence of AVX-512 makes me doubtful of that. Let's enumerate what Apple has access to in more detail: - third-party apps (in bytecode form) - first-party apps - the kernel - a vast array of performance-critical libraries - c/swift compilers - machine code optimizers - silicon design - product stakeholders The difference is that with Apple, the interaction between the various layers in the stack would be much lower friction than between Intel, AMD and Microsoft. The Apple Silicon team are truly single-customer. Equally as importantly, the Apple Product teams are truly single-buyer (eventually) and unlike Microsoft which has to split loyalties between Intel, AMD, ARM, and three dozen OEMs with their own motherboard designs tying all these bits together. And unlike Intel or Microsoft, everyone at every layer of Apple knows that their success will ultimately be judged on the same, singular metric: the quality/performance of the Apple product being released in September, and then the Apple product being released next March. That kind of unified focus is almost unheard of in the commodity PC space.
  - Mathnerd314 5y ago
    It's true that having a single stack makes things more efficient, but it also makes the process less adaptive. Although Apple seems to have a policy of buying out/copying successful software and integrating them into the OS, they can't buy everything. So eventually the more open/diverse ecosystem is going to have the better value proposition - a computer is a general-purpose device, and the less it can do the less useful it is. Of course this assumes Apple never gets market dominance where it surpasses all other companies combined, but phone sales are maybe 20% of the market and the laptop sales are only 8% of the market, so this doesn't seem likely to happen. tl;dr 80 developers working on an open stack, even with coordination friction, are going to outperform 20 developers on a closed stack.
    - zsmi 5y ago
      > are going to outperform Using what metric?
Traster 5y ago
I'm a little skeptical of this, this is the same as saying Tesla is going to have self-driving because they can record all the decisions current Teslas make. The truth is that it's very path dependent. For Tesla this means you can't optmize getting into the scenario in the first place and for Apple it means you can't actually know which code path will actually be regularly used.
- munk-a 5y ago
  For the general market perhaps - but let's say you're contracted to build self-driving trucks for UPS in particular and realize that UPS trucks almost never turn left[1] you could probably leverage that to decrease sensor density on one area of the vehicle since it's not as often used by your expected market - the vehicle might occasionally need to pause and do some extra work to make up for that deficiency but when the vehicle is on the happy path it can save some time. This example is pretty artificial - I can't really think of an optimization you could make knowing that you rarely turn left (maybe something with the axel?) but yea - more data means that you can turn your product to behave better in optimal situations - this comes at a cost but if you have a big stack of data you can make it so that your product generally wins that trade off most of the time. 1. https://www.bromfordlab.com/lab-diary/2019/4/9/why-do-ups-trucks-only-turn-right https://www.bromfordlab.com/lab-diary/2019/4/9/why-do-ups-tr...
  - rootusrootus 5y ago
    > This example is pretty artificial - I can't really think of an optimization you could make knowing that you rarely turn left (maybe something with the axel?) A real-world example are old NASCAR race cars. Optimized heavily for turning left, they were quite good at it at the expense of turning right.
stephencanon 5y ago
This is almost perfectly backwards. Intel does this sort of profiling _extensively_, and it guides their decision making to a fault. Apple's advantage in this regard is that the CPU architects can (and do) ask people writing software "if we made X faster, what could you do with it that you don't do today because it is slow?" That will never show up in a trace.

pvg 5y ago

Is that really such a unique advantage for Apple? Intel and AMD can work with Microsoft to achieve something similar, for instance.

bch 5y ago
I’m only speculating, but I’d think they wouldn’t even “have to work with” anybody - couldn’t they just instrument whatever they want?
- pvg 5y ago
  Sure, I just meant there's a Microsoft store so if the there was something particularly advantageous to having access to an app store, Intel or AMD are not completely in the wilderness here.
  - zsmi 5y ago
    Not completely in the wilderness sure. But they also have many operating systems to consider. The other obvious ones are Linux, BSD, and, until very recently, macOS. Are you sure it's possible to do a micro-optimization for one without nerfing the others?
    - ygra 5y ago
      Does the actual machine code doing computations really differ that much based on the OS? I'd guess the differences are just that you call different libraries and maybe a different calling convention, but nothing that would impact code running single-threaded without preemptions much.
      - zsmi 5y ago
        How the architecture handles the memory hierarchy is hugely important, but your example of calling conventions is a good one too. Keep in mind what calling conversions are: "Calling conventions act as a contract between subroutines at the assembly level." https://levelup.gitconnected.com/x86-calling-conventions-a34812afe097 https://levelup.gitconnected.com/x86-calling-conventions-a34...
simondotau 5y ago
It's also worth noting that Apple truly has the whole stack under their roof, including the team that maintains their C compiler and optimises LLVM's ARM machine code output. Intel has their own C compiler too, but one wonders to what extent they can profile real commercial software compiled using it, and feed that profiling knowledge back to the silicon designers in a useful way. The existence of AVX-512 makes me doubtful of that. Let's enumerate what Apple has access to in more detail: - third-party apps (in bytecode form) - first-party apps - the kernel - a vast array of performance-critical libraries - c/swift compilers - machine code optimizers - silicon design - product stakeholders The difference is that with Apple, the interaction between the various layers in the stack would be much lower friction than between Intel, AMD and Microsoft. The Apple Silicon team are truly single-customer. Equally as importantly, the Apple Product teams are truly single-buyer (eventually) and unlike Microsoft which has to split loyalties between Intel, AMD, ARM, and three dozen OEMs with their own motherboard designs tying all these bits together. And unlike Intel or Microsoft, everyone at every layer of Apple knows that their success will ultimately be judged on the same, singular metric: the quality/performance of the Apple product being released in September, and then the Apple product being released next March. That kind of unified focus is almost unheard of in the commodity PC space.
- Mathnerd314 5y ago
  It's true that having a single stack makes things more efficient, but it also makes the process less adaptive. Although Apple seems to have a policy of buying out/copying successful software and integrating them into the OS, they can't buy everything. So eventually the more open/diverse ecosystem is going to have the better value proposition - a computer is a general-purpose device, and the less it can do the less useful it is. Of course this assumes Apple never gets market dominance where it surpasses all other companies combined, but phone sales are maybe 20% of the market and the laptop sales are only 8% of the market, so this doesn't seem likely to happen. tl;dr 80 developers working on an open stack, even with coordination friction, are going to outperform 20 developers on a closed stack.
  - zsmi 5y ago
    > are going to outperform Using what metric?

Traster 5y ago

I'm a little skeptical of this, this is the same as saying Tesla is going to have self-driving because they can record all the decisions current Teslas make. The truth is that it's very path dependent. For Tesla this means you can't optmize getting into the scenario in the first place and for Apple it means you can't actually know which code path will actually be regularly used.

munk-a 5y ago
For the general market perhaps - but let's say you're contracted to build self-driving trucks for UPS in particular and realize that UPS trucks almost never turn left[1] you could probably leverage that to decrease sensor density on one area of the vehicle since it's not as often used by your expected market - the vehicle might occasionally need to pause and do some extra work to make up for that deficiency but when the vehicle is on the happy path it can save some time. This example is pretty artificial - I can't really think of an optimization you could make knowing that you rarely turn left (maybe something with the axel?) but yea - more data means that you can turn your product to behave better in optimal situations - this comes at a cost but if you have a big stack of data you can make it so that your product generally wins that trade off most of the time. 1. https://www.bromfordlab.com/lab-diary/2019/4/9/why-do-ups-trucks-only-turn-right https://www.bromfordlab.com/lab-diary/2019/4/9/why-do-ups-tr...
- rootusrootus 5y ago
  > This example is pretty artificial - I can't really think of an optimization you could make knowing that you rarely turn left (maybe something with the axel?) A real-world example are old NASCAR race cars. Optimized heavily for turning left, they were quite good at it at the expense of turning right.

stephencanon 5y ago

This is almost perfectly backwards. Intel does this sort of profiling _extensively_, and it guides their decision making to a fault. Apple's advantage in this regard is that the CPU architects can (and do) ask people writing software "if we made X faster, what could you do with it that you don't do today because it is slow?" That will never show up in a trace.