netdev - Re: [RFC PATCH 14/15] net: sched: make qstats per cpu

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Date:	Wed, 30 Apr 2014 10:08:01 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	Jamal Hadi Salim <jhs@...atatu.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [RFC PATCH 14/15] net: sched: make qstats per cpu

On Wed, Apr 30, 2014 at 9:40 AM, John Fastabend
<john.fastabend@...il.com> wrote:
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index 1a55e19..6d67a27 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -92,7 +92,10 @@ struct Qdisc {
>                 struct gnet_stats_basic_cpu __percpu *cpu_bstats;
>         } bstats_qdisc;
>         unsigned int            __state;
> -       struct gnet_stats_queue qstats;
> +       union {
> +               struct gnet_stats_queue qstats;
> +               struct gnet_stats_queue __percpu *cpu_qstats;
> +       } qstats_qdisc;
>         struct rcu_head         rcu_head;
>         int                     padded;
>         atomic_t                refcnt;


So only ingress qdisc uses ->cpu_qstats, the rest still uses
->qstats. Hmm, doesn't this mean ingress qdisc should init
->cpu_qstats in its ->init()?

[...]

> diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
> index 5700c27..2423d7b 100644
> --- a/net/sched/sch_ingress.c
> +++ b/net/sched/sch_ingress.c
> @@ -58,6 +58,7 @@ static struct tcf_proto **ingress_find_tcf(struct Qdisc *sch, unsigned long cl)
>  static int ingress_enqueue(struct sk_buff *skb, struct Qdisc *sch)
>  {
>         struct ingress_qdisc_data *p = qdisc_priv(sch);
> +       struct gnet_stats_queue *qstats;
>         struct tcf_result res;
>         struct tcf_proto *fl = rcu_dereference_bh(p->filter_list);
>         int result;
> @@ -68,7 +69,8 @@ static int ingress_enqueue(struct sk_buff *skb, struct Qdisc *sch)
>         switch (result) {
>         case TC_ACT_SHOT:
>                 result = TC_ACT_SHOT;
> -               sch->qstats.drops++;
> +               qstats = this_cpu_ptr(sch->qstats_qdisc.cpu_qstats);
> +               qstats->drops++;
>                 break;
>         case TC_ACT_STOLEN:
>         case TC_ACT_QUEUED:

I don't see you call alloc_percpu() and free_percpu() in sch_ingress.c.
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