Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 11 Oct 2023 14:54:45 -0700 | Subject | Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr() |
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On Wed, 11 Oct 2023 at 14:33, Uros Bizjak <ubizjak@gmail.com> wrote: > > Reading the above, it looks to me that we don't want to play games > with "const aliased" versions of current_task [1], as proposed by > Nadav in his patch series.
Well, maybe I'd like it if I saw what the effect of it was, but that patch mentions "sync_mm_rss()" which doesn't actually exist (SPLIT_RSS_COUNTING is never defined, the split version is gone and hasn't existed since commit f1a7941243c1 "mm: convert mm's rss stats into percpu_counter")
I'm not sure why gcc used to get code generation wrong there, and I don't see what could be improved in the current implementation of 'current_task', but I guess there could be things that could be done to make gcc more likely to CSE the cases..
IOW, I don't understand why Navad's patch would improve gcc code gen. It presumably depends on some gcc internal issue (ie "gcc just happens to be better at optimization X").
Which is obviously a valid thing in general.
Linus
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