Re: [PATCH 3/3] IPI: Avoid to use 2 cache lines for one call_single_data

[Huang\, Ying]

Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:
[snip]
> diff --git a/include/linux/smp.h b/include/linux/smp.h
> index 68123c1fe549..8d817cb80a38 100644
> --- a/include/linux/smp.h
> +++ b/include/linux/smp.h
> @@ -14,13 +14,16 @@
>  #include <linux/llist.h>
>  
>  typedef void (*smp_call_func_t)(void *info);
> -struct call_single_data {
> +struct __call_single_data {
>  	struct llist_node llist;
>  	smp_call_func_t func;
>  	void *info;
>  	unsigned int flags;
>  };
>  
> +typedef struct __call_single_data call_single_data_t
> +	__aligned(sizeof(struct __call_single_data));
> +

Another requirement of the alignment is that it should be the power of
2.  Otherwise, for example, if someone adds a field to struct, so that
the size becomes 40 on x86_64.  The alignment should be 64 instead of
40.

Best Regards,
Huang, Ying

>  /* total number of cpus in this system (may exceed NR_CPUS) */
>  extern unsigned int total_cpus;
>  
[snip]