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Apple Starts Alerting Users That It Will End 32-Bit App Support On the Mac (techcrunch.com)
An anonymous reader quotes a report from TechCrunch: Tomorrow at midnight PT, Apple will begin issuing an alert box when you open a 32-bit app in MacOS 10.13.4. It's a one-time (per app) alert, designed to help MacOS make the full transition to 64-bit. At some unspecified time in the future, the operating system will end its support for 32-bit technology meaning those apps that haven't been updated just won't work. That time, mind you, is not tomorrow, but the company's hoping that this messaging will help light a fire under users and developers to upgrade before that day comes. Says the company on its help page, "To ensure that the apps you purchase are as advanced as the Mac you run them on, all future Mac software will eventually be required to be 64-bit." As the company notes, the transition's been a long time coming. The company started making it 10 or so years ago with the Power Mac G5 desktop, so it hasn't exactly been an overnight ask for developers. Of course, if you've got older, non-supported software in your arsenal, the eventual end-of-lifing could put a severe damper on your workflow. For those users, there will no doubt be some shades of the transition from OS 9 to OS X in all of this.
To save a few GB in system libs? I realize that there are arch improvements in amd64 but that's no reason to break compatibility.
It's probably actually to reduce testing. It's still dumb. You're gonna have to run a VM to run 32 bit software. Even Microsoft is better at back compatibility than that. But Apple has never been shy about forcing its customers to spend more money, because they repeatedly demonstrate a willingness to do that — and they often give it to Apple.
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Yes, your company should account for that when it purchases technology. Everything gets old and dies, from people to computer programs. Not accounting for that fact is a problem in your business model. Are you still using a PDP11?
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I realize that there are arch improvements in amd64 but that's no reason to break compatibility.
64-bit on x86 royally sucks. Beside unavoidable issues related to 64-bit in general (twice as big pointers, thus any pointer-heavy structure taking twice as much memory, thus cache lines), on x86 in particular it's a dirty hack.
To get slower than amd64, you'd need an ancient register-starved ABI that passes way too much on stack, can't use floating point efficiently, may not pass 64-bit arguments when you actually need them, etc -- ie, i386.
Compare this with a modern 32-bit ABI on x86 (ie, x32). An average program takes ~2/3 memory to run, speed depending on how much pointers you use, but +7% is typical, over 40% in certain cases.
On architecture families that were designed with 64-bit in mind, most of this benefit disappears, but on x86 sane 32-bit wins handily.
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I had a look in activity monitor and I have 3 32-bit processes running and I found 3. Two were part of novaterm, which I installed years ago to do HP TouchPad development and haven't used since HP abandoned WebOS, but which I apparently left installing some daemons. The remaining one was the Android File Transfer agent, because apparently I haven't updated Android File Transfer since 2012 and it doesn't auto-update. After a small cleanup, I am now running none.
There's actually only one 32-bit application that I do care about: WINE. There's no reason that WINE couldn't be made to launch 32-bit Windows apps as a 64-bit binary though: it already includes its own program launcher and thunks for calling from Windows libraries into host-system ones.
The benefit is not just saving a few GBs of system libs. It's not having to do QA on any 32-bit versions of software. Apple's 64-bit Objective-C ABI is very different to its 32-bit one (small objects are hidden in pointers, reference counts are embedded in isa pointers, and so on). Making sure that none of the 100MBs or so of Objective-C frameworks that they ship have different observable behaviour with the different pointer sizes is a significant testing overhead. It's also a noticeable memory overhead if you run one app that pulls in the 32-bit versions of all of the system libraries. Even just the small set that you need to link to for any GUI application that adds up to around 50MB of object code, which is not shared with any of the 64-bit processes and so consumes L1 icache and L2/L3 cache space, making everything else slower.
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Memory space has nothing to do with it. 64-bit means a lot more general-purpose registers, 64-bit registers (x86-32 uses pairs of registers for 64-bit operations and typically requires a stack spill for each one), and PC-relative addressing (makes anything that uses shared libraries faster). Less relevant for Apple, because they never supported anything older than a Core 1, but it also typically means being able to assume SSE.
In all except for a few rare circumstances, x86-64 code is faster than x86-32 code on the same processor (the same does not apply to all other 32/64-bit architecture pairs). On top of the underlying improvements, there are a number of 64-bit-only optimisations in Apple's Objective-C implementation (and Objective-C code accounts for a very large proportion of their total code). The class pointer has a load of spare bits at the top, so reference counts are stored inline there. Small objects can be embedded in pointers (including small ASCII strings, which account for a large proportion of dictionary keys and can significantly reduce memory usage and improve performance).
Oh, and it's worth noting that there was a very small window when Apple shipped 32-bit x86 machines. For the Mac Mini, February 2006 to August 2007. For the MacBook, May 2006 to November 2006. For the MacBook Pro, January 2006 to October 2006. The last version of OS X to support the 32-bit chips was 10.6.8, released 8 years ago and discontinued (no more support updates) in July 2011.
Most people buying x86 Macs around the transition held off until the 64-bit ones, because it was pretty obvious at launch that Apple would move to 64-bit quickly (the lack of 64-bit mobile PowerPC chips was one of the reasons for their switch to Intel). XCode was able to produce 64-bit binaries and 32/64-bit fat binaries prior to the Intel switch and most Mac apps moved to being 64-bit a long time ago.
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Actually, I am.
The 32bit x86 version of MacOS was very short lived and was arguably a mistake...
Availability of 64bit PPC hardware to run OSX predates the 32bit x86 version, so they actually took a step backwards. The only non 64bit x86 macs are the very first model laptops, IIRC even the first gen mac pro was 64bit from the start.
Apple should never have supported 32bit x86 at all, and should have moved directly from PPC64 to x86_64.
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Legacy unmaintained code is a significant security risk...
64bit is not a new thing, 64bit processors have been around for nearly 30 years and have been mainstream for more than 10, apple have not produced a 32bit mac for more than 10 years now, and they are just starting to deprecate 32bit support, so 32bit apps will continue to run and be supported for a few years yet.
If you're running software that hasn't been updated in such a long time then you should seriously be considering replacing it with something that is actively maintained for many reasons.
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Compare this with a modern 32-bit ABI on x86 (ie, x32). An average program takes ~2/3 memory to run, speed depending on how much pointers you use, but +7% is typical, over 40% in certain cases.
I'd be very interested in where you get those numbers from. I work on a research architecture that uses 128-bit pointers and we find that in most cases your DRAM traffic increases by under 10% going from 64-bit to 128-bit. A 7% performance delta sounds about what I'd expect, but 2/3 more memory doesn't. That implies that around 2/3 of your memory is pointers - our measurements indicate that for most workloads (including most of SPEC) it's closer to 10-20% and the number goes down for more performance-critical workloads because developers try very hard to avoid pointer chasing (because it doesn't play well with modern pipelines) in such code.
With my FreeBSD hat on, I did a little bit of analysis of the x32 ABI and concluded that it is better for most systems only if you don't use the x64 ABI for anything. The performance hit from reduced cache sharing between processes for common shared libraries was greater than the performance win from x32. This was the same result that Sun Research found on SPARC 20 years earlier: the 32-bit ABI was better if everything used it, but if you use 1-2 64-bit programs then you lose more then you gain.
This is even more true on something like macOS, where there's a big shared memory region where all of the common system libraries are pre-loaded and then accessed via a per-process offset (and where the kernel is set up so that all mappings of this region share leaf page table entries and so reduce cache pressure on TLB misses).
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Any macOS dev who is actively developing their code will already be developing a 64-bit version. XCode has defaulted to fat binary (32/64-bit) builds since 2006 and on all versions of OS X since 2011 and any older version on a 64-bit chip the system will launch the 64-bit version in preference. You have to explicitly opt out of 64-bit support. It's far more common for developers to not bother with the 32-bit version.
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Memory space has nothing to do with it.
Not quite "nothing", thank you.
64-bit means a lot more general-purpose registers, 64-bit registers (x86-32 uses pairs of registers for 64-bit operations and typically requires a stack spill for each one), and PC-relative addressing (makes anything that uses shared libraries faster).
I know. Just wrote a bit of 32bit assembly that keeps the entire program state in registers. It emulates a rather more simple stack machine CPU.
But yes, enlarging the register file is what brought the big improvement in speed. Apparently the "CISC but RISC underneath"-marketeering was so much bullshit and the register file is a big fat bottleneck on x86. The 64bit register width isn't even that important since you don't really need more for most office and other "consumer" tasks anyway. Certainly not since as soon as you do need more bits the task turns out to be one for which there already is some extension or other to do the heavy lifting. The many extensions in x86 don't use the general register file.
But really, that's hardly relevant. What this is about is having programs that you got as a 32bit binary that work but somehow aren't updateable. Of course, apple typically doesn't care and just tells you to "upgrade", to a competitor's application if you have to, regardless of its cost to you.
Oh, and it's worth noting that there was a very small window when Apple shipped 32-bit x86 machines.
They probably should have refrained from doing that. They could've gone full 64bit from the start and not have to slam the door later. A little thought beforehand, etc.
Most people buying x86 Macs around the transition held off until the 64-bit ones, because it was pretty obvious at launch that Apple would move to 64-bit quickly (the lack of 64-bit mobile PowerPC chips was one of the reasons for their switch to Intel).
"We can't have 64bit mobile PowerPC chips so we'll ship 32bit wintendo mobile chips instead." This makes no sense.
For PowerPC the register file argument doesn't hold, by the by. Which is really the only thing that causes a big win outside scientific computing for x86 going from 32 to 64bit, certainly if "memory space has nothing to do with it."
Anyway, all that is rationalisation to the net effect of being less responsible than they could be, and I'm saying, you don't get to shout at the users of your "ecosystem" if you created your "ecosystem" to be this way.
Games are an example of software that doesn't usually get updated, but you still want them to keep working.
Frankly I wish programmers like you (who don't have respect for backwards compatibility) would crawl into a ditch and die, but I don't get everything I want in this world.
"First they came for the slanderers and i said nothing."
Yeah, but x32 linux is faster for pretty much everything than amd64 or i386, so it's not the "64-bit" that makes it faster, it's the "extra registers and instructions" Ditching the 64 bit pointers makes programs faster.
A large part of the Apple software stack is Objective-C. On 32-bit platforms, every object has a 32-bit reference count, which is stored in a look-aside table (which I think is an llvm::DenseMap now). Every reference count manipulation (which happens on almost every heap assignment of an object pointer) requires locking the table (or, at least, one of the tables - I think there are 8 on the desktop builds), looking up the refcount indexed by the object, and modifying it. On 64-bit platforms, Apple stores the reference count in the top 16 bits of the class pointer. Updating it is an atomic instruction.
When you create an NSString or NSNumber instance on 32-bit Apple platforms, you are creating an object on the heap. This requires a reference count in the table if it is ever retained (i.e. a pointer to it is stored on the heap), a 32-bit class pointer and at least 32 bits for the value, typically more. This space is probably rounded up to 16 bytes, for alignment. When you create an NSNumber instance or a short NSString on 64-bit Apple platforms, the value is embedded in the pointer. Creation is some bit twiddling in a register, no memory allocation. When I profiled some desktop applications some years ago (before Apple implemented this optimisation), I found that around 10% of all object allocations were strings that could be stored in a pointer. That saving alone is worth the 64-bit switch for most Objective-C applications.
Most JavaScript implementations see similar benefits on 64-bit, though from quite different implementation techniques.
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