FreeBSD phasing out 32-bit platforms

[Posted February 12, 2024 by jzb]

The FreeBSD Project has announced that it intends to deprecate 32-bit platforms "over the next couple of major releases".

We anticipate FreeBSD 15.0 will not include the armv6, i386, and powerpc platforms, and FreeBSD 16.0 will not include armv7. Support for executing 32-bit binaries on 64-bit kernels will be retained through at least the lifetime of the stable/16 branch if not longer.

The announcement notes that support for some 32-bit platforms "may be extended if there is both demand and commitment to increased developer resources". More details about the current plans for 32-bit platforms are available in the FreeBSD 14.0-RELEASE Release Notes.

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 0:58 UTC (Tue) by makendo (guest, #168314) [Link] (11 responses)

The use of new 32-bit-only designs seem to be in the embedded space only now. Can't gauge how many existing 32-bit general-purpose computers are still in use, though.

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 4:41 UTC (Tue) by wtarreau (subscriber, #51152) [Link] (10 responses)

I suspect it might still be common in high-densitiy containers or VM for the lower resource usage.

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 7:16 UTC (Tue) by WolfWings (subscriber, #56790) [Link] (6 responses)

For the broadly affected platforms (arm mostly) I just don't see that coming into play? There never were large-scale armv6 (most commonly Cortex M0 through M2) or even armv7 (most commonly Cortex M3 through M7) hypervisor scenarios AFAIK?

And on x86 even the 64-bit CPU modes run 32-bit data structures besides pointers, so outside of deeply pointer-centric workloads (which can still be worked around with relative addressing) there's no enormous difference in overall VM overcommit capacity, especially since FreeBSD doesn't have any sort of same-page merging support so it's just not used in that scenario compared to others?

And for high-density containerization the same applies even more-so from what I've seen, just normal library-sharing can offset a lot of the container base size for near-duplicate containers?

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 10:02 UTC (Tue) by pm215 (subscriber, #98099) [Link]

M0 is v6M and M3 to M7 are v7M - these M-profile CPUs are very different from v6 and v7 A-profile cores at the system level (exceptions, interrupts, etc), and there has never been any architectural support for virtualizing them. If you're using a hypervisor then your guest is A-profile, and these days almost certainly a 64 bit v8A guest, though some CPUs still have the support for virtualizing a 32-bit A-profile guest.

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 13:08 UTC (Tue) by wtarreau (subscriber, #51152) [Link] (4 responses)

I meant 32-bit userspace running in a 64-bit container mostly, though on x86 if you want to pack more VMs into the same machine, running smaller 32-bit VMs has its interest as well. And yes I agree that armv7 VMs are insignificant.

FreeBSD phasing out 32-bit platforms

Posted Feb 14, 2024 10:07 UTC (Wed) by taladar (subscriber, #68407) [Link]

That isn't really very useful considering how unmaintained x86 is now. Any small savings in the amount of memory used will be offset by the plethora of bugs you encounter on that platform only and the extra effort to compile code that upstream doesn't compile for that platform any more and similar problems.

FreeBSD phasing out 32-bit platforms

Posted Feb 15, 2024 15:30 UTC (Thu) by arnd (subscriber, #8866) [Link] (1 responses)

The release notes also say that "Support for executing 32-bit binaries on 64-bit platforms via the COMPAT_FREEBSD32 option will continue for at least the stable/15 and stable/16 branches", which means this remains possible for more than a decade, until FreeBSD 16 reaches its end of life, or they might keep it working if there is still demand.

Planning to end support for ARMv7 kernels and 32-bit userspace in the mid-2030s does not sound too aggressive.

FreeBSD phasing out 32-bit platforms

Posted Mar 1, 2024 4:07 UTC (Fri) by cgull (guest, #115681) [Link]

(Late to the party, but.)

Ah, you misunderstand. COMPAT_FREEBSD32 means loader and syscall shims for 32-bit executables in a 64-bit kernel. So 32-bit kernels are dead in FreeBSD, basically now, for development. I think even this 32-bit support might rot well before 2034.

FreeBSD is a much smaller project than Linux, and for most of its existence has been oriented more towards general-purpose servers and services, rather than small embedded platforms. It's not surprising to me that they'd drop 32-bit support now.

Personally, I'm fine with that. I started on the transition to 64-bit in 2009.

The only 32-bit Linux platform I'd somewhat trust now is ARM6/ARM7, because Raspberry Pi.

x64 VM needs motherboard support

Posted Feb 21, 2024 2:43 UTC (Wed) by gmatht (guest, #58961) [Link]

I seem to remember that I needed to flip an option on my motherboard to emulate x64 VMs. One small argument in favor of i386 VMs.

I also remember that Intel atoms got x64 support relatively late. I have an i386 only 2G laptop lying around. Still the last 32bit Lincroft atom came out in 2011, so they are reaching EOL now. Intel still makes 32bit chips but they aren't the sort of thing you'd run a distro on.

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 13:57 UTC (Tue) by makendo (guest, #168314) [Link] (2 responses)

I was talking about running 32-bit kernels on 64-bit-capable boxes, bare-metal. Still works in modern x86 processors (x86S is not here yet), but hardly meaningful given constraints on virtual memory (4GiB) and "physical" address space (64GiB in x86-32) -- for contemporary desktops, the former makes juggling between page entries and/or page tables a hard requirement, the latter places a low limit on the amount of RAM and set of devices you can use.

For VMs, many of them don't need a lot of memory to begin with, so the halved space requirement for pointers outweighs the potential page-table-thrashing concerns.

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 21:28 UTC (Tue) by willy (subscriber, #9762) [Link] (1 responses)

I forget, do you get NX bit in that configuration?

FreeBSD phasing out 32-bit platforms

Posted Feb 13, 2024 23:12 UTC (Tue) by intelfx (subscriber, #130118) [Link]

If I recall correctly, PAE is the _only_ way you get NX bit with non-amd64 x86.