Linux 5.14 Bringing A Major Cleanup To The x86 FPU Code

[phoronix]

Phoronix: Linux 5.14 Bringing A Major Cleanup To The x86 FPU Code

The Linux 5.14 kernel so far is running smoothly in my early tests across a variety of systems but coming in this morning is a pull request having the potential to cause some fall-out on x86/x86_64 systems but hopefully will not...

https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.14-x86-FPU-Cleanup

[tildearrow]

Typo:

but more pressing is a a major cleanup of the x86 FPU code.

[schmidtbag]

I imagine cleaning up such low level code would result in some performance increase. Probably not much, but maybe in some cases a noteworthy amount.

[Vorpal]

There is a lot of talk of Intel here, but has it been properly tested on the other major x86 implementation? I don't know how much these have in common when it comes to this (virtualisation differs for example), but at least the x87 instruction set should be old enough that there is a lot of commonality surely?

[coder]

I imagine cleaning up such low level code would result in some performance increase. Probably not much, but maybe in some cases a noteworthy amount.

It's kernel, though. So, the most it could affect would probably be just reducing the overhead of syscalls and context switches by a little.

[coder]

at least the x87 instruction set should be old enough that there is a lot of commonality surely?

They didn't say x87. Not in the article, anyhow.

[AlDunsmuir]

They didn't say x87. Not in the article, anyhow.

Reference would be back to 8086 days when the 8087 FPU was a separate optional IC.

[coder]

Reference would be back to 8086 days when the 8087 FPU was a separate optional IC.

I know about the 8087.

Anyway, the patch explicitly mentions AVX512. So, that proves it's not limited to x87.

http://lkml.iu.edu/hypermail/linux/kernel/2107.0/05120.html

[Vorpal]

Thanks for the clarifications, I did not delve into the details of the patch set given that I was reading this on my phone.