Re: [TECH TOPIC] Reaching consensus on CONFIG_HIGHMEM phaseout

H. Peter Anvin
2025-09-09T22:39:37Z

On September 9, 2025 3:24:29 PM PDT, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>On Tue, 9 Sept 2025 at 14:39, H. Peter Anvin <hpa@zytor.com> wrote:
>>
>> 1 GB systems used highmem too, sadly. And 1 GB was the norm for a big chuck of the late 32-bit era.
>
>Well, while on x86 1GB systems did use highmem, they'd typically not
>use very much of it.
>
>IOW, they'd have about 900MB as lowmem (ok, I think it was 896MB to be
>exact), with something like 120MB highmem.
>
>So they'd either lose a bit of memory, or they'd use the 2G:2G split.
>
>Or - and I think this is the main point - they'd stay on old kernels
>like the ancient museum pieces they are.
>
>I'm not convinced it makes sense to have a modern kernel on a museum piece.
>
> Linus
>

Certainly. And the 2:2 split is probably the right thing for the old machines anyway.