netdev - Re: [PATCH net-next] net: minor optimization in qdisc_qstats_cpu

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Message-ID: <f4e3fe14-ddbb-5b37-d003-46f28f7d8750@hpe.com>
Date:   Wed, 24 Aug 2016 11:04:43 -0700
From:   Rick Jones <rick.jones2@....com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        John Fastabend <john.r.fastabend@...el.com>
Subject: Re: [PATCH net-next] net: minor optimization in
 qdisc_qstats_cpu_drop()

On 08/24/2016 10:23 AM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> per_cpu_inc() is faster (at least on x86) than per_cpu_ptr(xxx)++;

Is it possible it is non-trivially slower on other architectures?

rick jones

>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  include/net/sch_generic.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index 0d501779cc68f9426e58da6d039dd64adc937c20..52a2015667b49c8315edbb26513a98d4c677fee5 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -592,7 +592,7 @@ static inline void qdisc_qstats_drop(struct Qdisc *sch)
>
>  static inline void qdisc_qstats_cpu_drop(struct Qdisc *sch)
>  {
> -	qstats_drop_inc(this_cpu_ptr(sch->cpu_qstats));
> +	this_cpu_inc(sch->cpu_qstats->drops);
>  }
>
>  static inline void qdisc_qstats_overlimit(struct Qdisc *sch)
>