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net: rps: change input_queue_tail_incr_save()

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input_queue_tail_incr_save() is incrementing the sd queue_tail
and save it in the flow last_qtail.

Two issues here :

- no lock protects the write on last_qtail, we should use appropriate
  annotations.

- We can perform this write after releasing the per-cpu backlog lock,
  to decrease this lock hold duration (move away the cache line miss)

Also move input_queue_head_incr() and rps helpers to include/net/rps.h,
while adding rps_ prefix to better reflect their role.

v2: Fixed a build issue (Jakub and kernel build bots)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2024-03-29 15:42:23 +00:00 committed by David S. Miller
parent f7efd01fe2
commit 36b83ffcf2
3 changed files with 35 additions and 23 deletions
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15
include/linux/netdevice.h
View file

@ -3250,21 +3250,6 @@ struct softnet_data {
call_single_data_t defer_csd;
};
static inline void input_queue_head_incr(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
sd->input_queue_head++;
#endif
}
static inline void input_queue_tail_incr_save(struct softnet_data *sd,
unsigned int *qtail)
{
#ifdef CONFIG_RPS
*qtail = ++sd->input_queue_tail;
#endif
}
DECLARE_PER_CPU_ALIGNED(struct softnet_data, softnet_data);
static inline int dev_recursion_level(void)

23
include/net/rps.h
View file

@ -122,4 +122,27 @@ static inline void sock_rps_record_flow(const struct sock *sk)
#endif
}
static inline u32 rps_input_queue_tail_incr(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
return ++sd->input_queue_tail;
#else
return 0;
#endif
}
static inline void rps_input_queue_tail_save(u32 *dest, u32 tail)
{
#ifdef CONFIG_RPS
WRITE_ONCE(*dest, tail);
#endif
}
static inline void rps_input_queue_head_incr(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
sd->input_queue_head++;
#endif
}
#endif /* _NET_RPS_H */

20
net/core/dev.c
View file

@ -4611,7 +4611,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
if (unlikely(tcpu != next_cpu) &&
(tcpu >= nr_cpu_ids || !cpu_online(tcpu) ||
((int)(per_cpu(softnet_data, tcpu).input_queue_head -
rflow->last_qtail)) >= 0)) {
READ_ONCE(rflow->last_qtail))) >= 0)) {
tcpu = next_cpu;
rflow = set_rps_cpu(dev, skb, rflow, next_cpu);
}
@ -4666,7 +4666,7 @@ bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index,
cpu = READ_ONCE(rflow->cpu);
if (rflow->filter == filter_id && cpu < nr_cpu_ids &&
((int)(per_cpu(softnet_data, cpu).input_queue_head -
rflow->last_qtail) <
READ_ONCE(rflow->last_qtail)) <
(int)(10 * flow_table->mask)))
expire = false;
}
@ -4801,6 +4801,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
unsigned long flags;
unsigned int qlen;
int max_backlog;
u32 tail;
reason = SKB_DROP_REASON_DEV_READY;
if (!netif_running(skb->dev))
@ -4825,8 +4826,11 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
napi_schedule_rps(sd);
}
__skb_queue_tail(&sd->input_pkt_queue, skb);
input_queue_tail_incr_save(sd, qtail);
tail = rps_input_queue_tail_incr(sd);
backlog_unlock_irq_restore(sd, &flags);
/* save the tail outside of the critical section */
rps_input_queue_tail_save(qtail, tail);
return NET_RX_SUCCESS;
}
@ -5904,7 +5908,7 @@ static void flush_backlog(struct work_struct *work)
if (skb->dev->reg_state == NETREG_UNREGISTERING) {
__skb_unlink(skb, &sd->input_pkt_queue);
dev_kfree_skb_irq(skb);
input_queue_head_incr(sd);
rps_input_queue_head_incr(sd);
}
}
backlog_unlock_irq_enable(sd);
@ -5913,7 +5917,7 @@ static void flush_backlog(struct work_struct *work)
if (skb->dev->reg_state == NETREG_UNREGISTERING) {
__skb_unlink(skb, &sd->process_queue);
kfree_skb(skb);
input_queue_head_incr(sd);
rps_input_queue_head_incr(sd);
}
}
local_bh_enable();
@ -6041,7 +6045,7 @@ static int process_backlog(struct napi_struct *napi, int quota)
rcu_read_lock();
__netif_receive_skb(skb);
rcu_read_unlock();
input_queue_head_incr(sd);
rps_input_queue_head_incr(sd);
if (++work >= quota)
return work;
@ -11455,11 +11459,11 @@ static int dev_cpu_dead(unsigned int oldcpu)
/* Process offline CPU's input_pkt_queue */
while ((skb = __skb_dequeue(&oldsd->process_queue))) {
netif_rx(skb);
input_queue_head_incr(oldsd);
rps_input_queue_head_incr(oldsd);
}
while ((skb = skb_dequeue(&oldsd->input_pkt_queue))) {
netif_rx(skb);
input_queue_head_incr(oldsd);
rps_input_queue_head_incr(oldsd);
}
return 0;