On 15-07-02 06:07 AM, Eric Dumazet wrote:
> Final step for gact RCU operation :
>
> 1) Use percpu stats
> 2) update lastuse only every clock tick
> 3) Remove spinlock acquisition, as it is no longer needed.
>
> Since this is the last contended lock in packet RX when tc gact is used,
> this gives impressive gain.
>
> My host with 8 RX queues was handling 5 Mpps before the patch,
> and more than 10 Mpps after patch.
>
> Tested:
>
> On receiver :
> IP=ip
> TC=tc
> dev=eth0
>
> $TC qdisc del dev $dev ingress 2>/dev/null
> $TC qdisc add dev $dev ingress
> $TC filter del dev $dev root pref 10 2>/dev/null
> $TC filter del dev $dev pref 10 2>/dev/null
> tc filter add dev $dev est 1sec 4sec parent ffff: protocol ip prio 1 \
> u32 match ip src 7.0.0.0/8 flowid 1:15 action drop
>
> Sender sends packets flood from 7/8 network
>
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Cc: Alexei Starovoitov <a...@plumgrid.com>
> Cc: Jamal Hadi Salim <j...@mojatatu.com>
> Cc: John Fastabend <john.fastab...@gmail.com>
> ---
> net/sched/act_gact.c | 14 ++++++--------
> 1 file changed, 6 insertions(+), 8 deletions(-)
[...]
> @@ -121,9 +121,8 @@ static int tcf_gact(struct sk_buff *skb, const struct
> tc_action *a,
> struct tcf_result *res)
> {
> struct tcf_gact *gact = a->priv;
> - int action = gact->tcf_action;
> + int action = READ_ONCE(gact->tcf_action);
>
> - spin_lock(&gact->tcf_lock);
> #ifdef CONFIG_GACT_PROB
> {
> u32 ptype = READ_ONCE(gact->tcfg_ptype);
> @@ -132,12 +131,11 @@ static int tcf_gact(struct sk_buff *skb, const struct
> tc_action *a,
> action = gact_rand[ptype](gact);
> }
> #endif
> - gact->tcf_bstats.bytes += qdisc_pkt_len(skb);
> - gact->tcf_bstats.packets++;
> + bstats_cpu_update(this_cpu_ptr(gact->common.cpu_bstats), skb);
> if (action == TC_ACT_SHOT)
> - gact->tcf_qstats.drops++;
> - gact->tcf_tm.lastuse = jiffies;
> - spin_unlock(&gact->tcf_lock);
> + qstats_drop_inc(this_cpu_ptr(gact->common.cpu_qstats));
> + if (gact->tcf_tm.lastuse != jiffies)
> + gact->tcf_tm.lastuse = jiffies;
I'm missing the point of the if block. Is that really good enough
for the 32bit system case? I would have expected some wrapper to
handle it here something like u64_stats_() maybe _u64_jiffies(). Maybe
after a coffee I'll make sense of it.
>
> return action;
> }
>
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