Re: [PATCH 1/5] x86/percpu: Differentiate this_cpu_{}() and __this_cpu_{}()

From: Linus Torvalds
Date: Wed Feb 27 2019 - 12:38:28 EST

On Wed, Feb 27, 2019 at 9:34 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> But the ONCE thing defeats CSE (on purpose!) so for code-gen that
> likes/wants that we then have to use the __this_cpu crud.

Right. But I do think that if you want CSE on a percpu access, you
might want to write it as such (ie load the value once and then re-use
the value).

But I'm not sure exactly which accesses Nadav noticed to be a problem,
so.. I guess I should just look at the other patches, but I found them
rather nasty and ad-hoc too so I just skimmed them with an "eww" ;)