Re: [GIT PULL] Ceph updates for 5.20-rc1

[Nick Desaulniers]

On Sun, Aug 14, 2022 at 1:29 PM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> I dug into it some more, and it is really "load_unaligned_zeropad()"
> that makes clang really uncomfortable.
>
> The problem ends up being that clang sees that it's inside that inner
> loop, and tries very hard to optimize the shift-and-mask that happens
> if the exception happens.
>
> The fact that the exception *never* happens unless DEBUG_PAGEALLOC is
> enabled - and very very seldom even then - is not something we can
> really explain to clang.

Probably if we could express that the do_exception label in
load_unaligned_zeropad was cold then that might help.
https://github.com/llvm/llvm-project/issues/46831

Otherwise, could we put the exceptional case statements in a noinline
or cold attributed function?
-- 
Thanks,
~Nick Desaulniers