Re: [PATCH net-next] net/sched: get rid of qdisc->padded

[Jakub Kicinski]

On Wed,  7 Oct 2020 09:51:11 -0700 Eric Dumazet wrote:
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index 
> 6c762457122fd0091cb0f2bf41bda73babc4ac12..d8fd8676fc724110630904909f64d7789f3a4b47
>  100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -91,7 +91,7 @@ struct Qdisc {
>       struct net_rate_estimator __rcu *rate_est;
>       struct gnet_stats_basic_cpu __percpu *cpu_bstats;
>       struct gnet_stats_queue __percpu *cpu_qstats;
> -     int                     padded;
> +     int                     pad;
>       refcount_t              refcnt;
>  
>       /*

Hi Eric!

Why keep the pad field? the member to lines down is
__cacheline_aligned, so we shouldn't have to manually 
push things out?

        struct gnet_stats_queue __percpu *cpu_qstats;                           
        int                     pad;                                            
        refcount_t              refcnt;                                         
                                                                                
        /*                                                                      
         * For performance sake on SMP, we put highly modified fields at the 
end                                                                             
  
         */                                                                     
        struct sk_buff_head     gso_skb ____cacheline_aligned_in_smp;