On Mon, Aug 24, 2020 at 10:11:05AM -0500, Yazen Ghannam wrote:
> Thanks. Yeah, they're identical:
> text data bss dec hex filename
> 15710076 13519306 5398528 34627910 2106146
> vmlinux-32banks
> 15710076 13519306 5398528 34627910 2106146
> vmlinux-64banks
So I went crazy here and built allmodconfigs for hypothetical CPUs which
support up to 4K MCA banks:
text data bss dec hex filename
24618040 27211906 35409988 87239934 5332cfe
vmlinux-32banks
24618040 27211906 35409988 87239934 5332cfe
vmlinux-64banks
24618040 27211906 35409988 87239934 5332cfe
vmlinux-128banks
For the first three - up to 128 banks, the sizes don't change.
24618000 27216002 35401796 87235798 5331cd6
vmlinux-256banks
Somewhere after 128 banks, it grows the data section but by exactly 4K,
i.e., one more page:
27216002 - 27211906 = 4096
The last page is not full, of course.
27216002 % 4096 = 2178
27211906 % 4096 = 2178
24618000 27220098 35401796 87239894 5332cd6
vmlinux-512banks
The same happens here.
27220098 - 27216002 = 4096
27220098 % 4096 = 2178
And so on:
24618000 27228290 35393604 87239894 5332cd6
vmlinux-1024banks
24618000 27244674 35377220 87239894 5332cd6
vmlinux-2048banks
24618000 27277442 35344452 87239894 5332cd6
vmlinux-4Kbanks
So what I think happens is, the first 128 banks fit within the same
.data section page thus vmlinux doesn't increase.
I guess there might be a .config which could cause that data increase
when the 32->64 banks move won't fit in the last .data page. It depends
on where those ~2K you computed and I snipped, land.
But since most kernels are allmodconfig builds, I guess we should be
fine.
So yeah, I guess we can take this one after you summarize the findings
of this thread in v2's commit message. :-)
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
