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SubjectRe: [PATCH] numa: mark __next_node() as __always_inline to fix section mismatch
On Mon, Dec 6, 2021 at 8:19 AM Alexander Lobakin
<alexandr.lobakin@intel.com> wrote:
>
> Clang (13) uninlines __next_node() which emits the following warning
> due to that this function is used in init code (amd_numa_init(),
> sched_init_numa() etc.):
>
> WARNING: modpost: vmlinux.o(.text+0x927ee): Section mismatch
> in reference from the function __next_node() to the variable
> .init.data:numa_nodes_parsed
> The function __next_node() references
> the variable __initdata numa_nodes_parsed.
> This is often because __next_node lacks a __initdata
> annotation or the annotation of numa_nodes_parsed is wrong.
>
> Mark __next_node() as __always_inline() so it won't get uninlined.
> bloat-o-meter over x86_64 binaries says this:
>
> scripts/bloat-o-meter -c vmlinux.baseline vmlinux
> add/remove: 1/1 grow/shrink: 2/7 up/down: 446/-2166 (-1720)
> Function old new delta
> apply_wqattrs_cleanup - 410 +410
> amd_numa_init 814 842 +28
> sched_init_numa 1338 1346 +8
> find_next_bit 38 19 -19
> __next_node 45 - -45
> apply_wqattrs_prepare 1069 799 -270
> wq_nice_store 688 414 -274
> wq_numa_store 805 433 -372
> wq_cpumask_store 789 402 -387
> apply_workqueue_attrs 538 147 -391
> workqueue_set_unbound_cpumask 947 539 -408
> Total: Before=14422603, After=14420883, chg -0.01%
>
> So it's both win-win in terms of resolving section mismatch and
> saving some text size (-1.7 Kb is quite nice).
>
> Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>

Thanks for the patch. See this thread:
https://github.com/ClangBuiltLinux/linux/issues/1302

There's a lot more instances of these based on config. Something like
https://github.com/ClangBuiltLinux/linux/issues/1302#issuecomment-807260475
would be more appropriate for fixing all instances, but I think this
is more so an issue with the inline cost model in LLVM.

I need to finish off https://reviews.llvm.org/D111456, and request
that https://reviews.llvm.org/D111272 which landed in clang-14 get
backported to the 13.0.1 release which should also help.

> ---
> include/linux/nodemask.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> index 567c3ddba2c4..55ba2c56f39b 100644
> --- a/include/linux/nodemask.h
> +++ b/include/linux/nodemask.h
> @@ -266,7 +266,7 @@ static inline int __first_node(const nodemask_t *srcp)
> }
>
> #define next_node(n, src) __next_node((n), &(src))
> -static inline int __next_node(int n, const nodemask_t *srcp)
> +static __always_inline int __next_node(int n, const nodemask_t *srcp)
> {
> return min_t(int,MAX_NUMNODES,find_next_bit(srcp->bits, MAX_NUMNODES, n+1));
> }
> --
> 2.33.1
>


--
Thanks,
~Nick Desaulniers

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