netdev_rx_queue表示对应的接收队列,很多网卡硬件上已经支持多个队列,此时就会有多个netdev_rx_queue队列,这个结构是挂在net_device,初始化接收队列的函数:netif_alloc_rx_queues
netif_alloc_rx_queues
-
static int netif_alloc_rx_queues(struct net_device *dev)
-
{
-
/*获取接收队列的个数*/
-
unsigned int i, count = netdev_extended(dev)->rps_data.num_rx_queues;
-
struct netdev_rx_queue *rx;
-
-
BUG_ON(count < 1);
-
/*分配netdev_rx_queue 空间*/
-
rx = kcalloc(count, sizeof(struct netdev_rx_queue), GFP_KERNEL);
-
if (!rx) {
-
pr_err("netdev: Unable to allocate %u rx queues.\n", count);
-
return -ENOMEM;
-
}
-
/* netdev_rx_queue 和net_device关联起来。*/
-
netdev_extended(dev)->rps_data._rx = rx;
-
/*对netdev_rx_queue 中net_device进行赋值操作*/
-
for (i = 0; i < count; i++)
-
rx[i].dev = dev;
-
return 0;
-
}
-
-
struct netdev_rx_queue {
-
/*保存当前队列的rps map*/
-
struct rps_map *rps_map;
-
/* //每个设备的队列保存了一个rps_dev_flow_table */
-
struct rps_dev_flow_table *rps_flow_table;
-
//对应的kobject
-
struct kobject kobj;
-
/*所属的net_device*/
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struct net_device *dev;
-
} ____cacheline_aligned_in_smp;
-
-
-
struct rps_map {
-
/*CPU的个数,也就是CPU数组的个数*/
-
unsigned int len;
-
struct rcu_head rcu;
-
/*保存了CPU的ID*/
-
u16 cpus[0];
-
};
get_rps_cpu
-
static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
-
struct rps_dev_flow **rflowp)
-
{
-
struct ipv6hdr *ip6;
-
struct iphdr *ip;
-
struct netdev_rx_queue *rxqueue;
-
struct rps_map *map;
-
struct rps_dev_flow_table *flow_table;
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struct rps_sock_flow_table *sock_flow_table;
-
struct netdev_rps_info *rpinfo = &netdev_extended(dev)->rps_data;
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int cpu = -1;
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int tcpu;
-
u8 ip_proto;
-
u32 addr1, addr2, ports, ihl;
-
-
rcu_read_lock();
-
-
if (skb_rx_queue_recorded(skb)) {
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/*获取设备对应的rx队列。*/
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u16 index = skb_get_rx_queue(skb);
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if (unlikely(index >= rpinfo->num_rx_queues)) {
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WARN_ONCE(rpinfo->num_rx_queues > 1, "%s received packet "
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"on queue %u, but number of RX queues is %u\n",
-
dev->name, index, rpinfo->num_rx_queues);
-
goto done;
-
}
-
rxqueue = rpinfo->_rx + index;
-
} else
-
rxqueue = rpinfo->_rx;
-
-
if (!rxqueue->rps_map && !rxqueue->rps_flow_table)
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goto done;
-
-
if (skb->rxhash) //如果硬件已经计算过,则直接跳过,不需要计算HASH值
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goto got_hash; /* Skip hash computation on packet header */
-
-
switch (skb->protocol) { /*根据不同的IP协议获取源IP和目的IP*/
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case __constant_htons(ETH_P_IP):
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if (!pskb_may_pull(skb, sizeof(*ip)))
-
goto done;
-
-
ip = (struct iphdr *) skb->data;
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ip_proto = ip->protocol;
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addr1 = ip->saddr;
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addr2 = ip->daddr;
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ihl = ip->ihl;
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break;
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case __constant_htons(ETH_P_IPV6):
-
if (!pskb_may_pull(skb, sizeof(*ip6)))
-
goto done;
-
-
ip6 = (struct ipv6hdr *) skb->data;
-
ip_proto = ip6->nexthdr;
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addr1 = ip6->saddr.s6_addr32[3];
-
addr2 = ip6->daddr.s6_addr32[3];
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ihl = (40 >> 2);
-
break;
-
default:
-
goto done;
-
}
-
ports = 0;
-
switch (ip_proto) {
-
case IPPROTO_TCP:
-
case IPPROTO_UDP:
-
case IPPROTO_DCCP:
-
case IPPROTO_ESP:
-
case IPPROTO_AH:
-
case IPPROTO_SCTP:
-
case IPPROTO_UDPLITE:
-
if (pskb_may_pull(skb, (ihl * 4) + 4))
-
ports = *((u32 *) (skb->data + (ihl * 4))); /*获取四层协议的端口号,tcp头的前4个字节就是源和目的端口,因此这里跳过ip头得到tcp头的前4个字节*/
-
break;
-
-
default:
-
break;
-
}
-
/*根据获取到的SIP和DIP,PORT计算HSAH值,*/
-
skb->rxhash = jhash_3words(addr1, addr2, ports, hashrnd) >> 16;
-
if (!skb->rxhash)
-
skb->rxhash = 1;
-
-
got_hash:
-
/* rps_sock_flow_table和rps_dev_flow_table 是为了解决RFS而添加的两张表,rps_sock_flow_table是一个全局的hash表,这个表针对socket的,映射了socket对应的cpu,这里的cpu就是应用层期待软中断所在的cpu ,rps_dev_flow_table,这个是针对设备的,每个设备队列都含有一个rps_dev_flow_table(这个表主要是保存了上次处理相同链接上的skb所在的cpu),这个hash表中每一个元素包含了一个cpu id,一个tail queue的计数器*/
-
flow_table = rcu_dereference(rxqueue->rps_flow_table);
-
sock_flow_table = rcu_dereference(rps_sock_flow_table);
-
if (flow_table && sock_flow_table) {
-
u16 next_cpu;
-
struct rps_dev_flow *rflow;
-
-
rflow = &flow_table->flows[skb->rxhash & flow_table->mask];
-
tcpu = rflow->cpu;
-
-
next_cpu = sock_flow_table->ents[skb->rxhash &
-
sock_flow_table->mask];
-
-
/*首先会得到两个flow table,一个是sock_flow_table,另一个是设备的rps_flow_table(skb对应的设备队列中对应的flow table),这里的逻辑是这样子的取出来两个cpu,一个是根据rps计算数据包前一次被调度过的cpu(tcpu),一个是应用程序期望的cpu(next_cpu),然后比较这两个值,如果 1 tcpu未设置(等于RPS_NO_CPU) 2 tcpu是离线的 3 tcpu的input_queue_head大于rps_flow_table中的last_qtail 的话就调度这个skb到next_cpu.而这里第三点input_queue_head大于rps_flow_table则说明在当前的dev flow table中的数据包已经发送完毕,否则的话为了避免乱序就还是继续使用tcpu
-
* If the desired CPU (where last recvmsg was done) is
-
* different from current CPU (one in the rx-queue flow
-
* table entry), switch if one of the following holds:
-
* - Current CPU is unset (equal to RPS_NO_CPU).
-
* - Current CPU is offline.
-
* - The current CPU's queue tail has advanced beyond the
-
* last packet that was enqueued using this table entry.
-
* This guarantees that all previous packets for the flow
-
* have been dequeued, thus preserving in order delivery.
-
*/
-
if (unlikely(tcpu != next_cpu) &&
-
(tcpu == RPS_NO_CPU || !cpu_online(tcpu) ||
-
((int)(per_cpu(softnet_data, tcpu).input_queue_head -
-
rflow->last_qtail)) >= 0)) {
-
tcpu = rflow->cpu = next_cpu;
-
if (tcpu != RPS_NO_CPU)
-
rflow->last_qtail = per_cpu(softnet_data,
-
tcpu).input_queue_head;
-
}
-
if (tcpu != RPS_NO_CPU && cpu_online(tcpu)) {
-
*rflowp = rflow;
-
/*设置返回的CPU*/
-
cpu = tcpu;
-
goto done;
-
}
-
}
-
/*当第一次进来时tcpu是RPS_NO_CPU,并且next_cpu也是RPS_NO_CPU,此时会导致跳过rfs处理,而是直接使用rps的处理, */
-
map = rcu_dereference(rxqueue->rps_map);
-
if (map) {
-
tcpu = map->cpus[((u32) (skb->rxhash * map->len)) >> 16];
-
/*如果cpu是online的,则返回计算出的这个cpu */
-
if (cpu_online(tcpu)) {
-
cpu = tcpu;
-
goto done;
-
}
-
}
-
-
done:
-
rcu_read_unlock();
-
return cpu;
-
}
-
-
/*将skb挂在到对应cpu的input queue上的, enqueue_to_backlog接受一个skb和cpu为参数,通过cpu来判断skb如何处理。要么加入所属的input_pkt_queue中,要么schecule 软中断*/
enqueue_to_backlog
-
static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
-
unsigned int *qtail)
-
{
-
struct softnet_data *queue;
-
unsigned long flags;
-
/*根据传递过来的CPU,获取softnet_data结构体*/
-
queue = &per_cpu(softnet_data, cpu);
-
-
local_irq_save(flags);
-
__get_cpu_var(netdev_rx_stat).total++;
-
-
spin_lock(&queue->input_pkt_queue.lock);
-
if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {
-
if (queue->input_pkt_queue.qlen) {
-
enqueue:/*将数据包添加到input_pkt_queue队列中*/
-
__skb_queue_tail(&queue->input_pkt_queue, skb);
-
*qtail = queue->input_queue_head +
-
queue->input_pkt_queue.qlen;
-
-
spin_unlock_irqrestore(&queue->input_pkt_queue.lock,
-
flags);
-
return NET_RX_SUCCESS;
-
}
-
-
/* Schedule NAPI for backlog device 可以调度软中断*/
-
if (napi_schedule_prep(&queue->backlog)) {
-
if (cpu != smp_processor_id()) {/*判断该SKB是否该CPU处理*/
-
struct rps_remote_softirq_cpus *rcpus =
-
&__get_cpu_var(rps_remote_softirq_cpus);
-
-
cpu_set(cpu, rcpus->mask[rcpus->select]);
-
__raise_softirq_irqoff(NET_RX_SOFTIRQ);
-
} else
-
/*应该当前cpu处理,则直接schedule 软中断,这里可以看到传递进去的是backlog */
-
____napi_schedule(queue, &queue->backlog);
-
}
-
goto enqueue;
-
}
-
-
spin_unlock(&queue->input_pkt_queue.lock);
-
-
__get_cpu_var(netdev_rx_stat).dropped++;
-
local_irq_restore(flags);
-
-
kfree_skb(skb);
-
return NET_RX_DROP;
-
}
enqueue_to_backlog
-
static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
-
unsigned int *qtail)
-
{
-
struct softnet_data *queue;
-
unsigned long flags;
-
/*根据传递过来的CPU,获取softnet_data结构体*/
-
queue = &per_cpu(softnet_data, cpu);
-
-
local_irq_save(flags);
-
__get_cpu_var(netdev_rx_stat).total++;
-
-
spin_lock(&queue->input_pkt_queue.lock);
-
if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {
-
if (queue->input_pkt_queue.qlen) {
-
enqueue:/*将数据包添加到input_pkt_queue队列中*/
-
__skb_queue_tail(&queue->input_pkt_queue, skb);
-
*qtail = queue->input_queue_head +
-
queue->input_pkt_queue.qlen;
-
-
spin_unlock_irqrestore(&queue->input_pkt_queue.lock,
-
flags);
-
return NET_RX_SUCCESS;
-
}
-
-
/* Schedule NAPI for backlog device 可以调度软中断*/
-
if (napi_schedule_prep(&queue->backlog)) {
-
if (cpu != smp_processor_id()) {/*判断该SKB是否该CPU处理*/
-
struct rps_remote_softirq_cpus *rcpus =
-
&__get_cpu_var(rps_remote_softirq_cpus);
-
-
cpu_set(cpu, rcpus->mask[rcpus->select]);
-
__raise_softirq_irqoff(NET_RX_SOFTIRQ);
-
} else
-
/*应该当前cpu处理,则直接schedule 软中断,这里可以看到传递进去的是backlog */
-
____napi_schedule(queue, &queue->backlog);
-
}
-
goto enqueue;
-
}
-
-
spin_unlock(&queue->input_pkt_queue.lock);
-
-
__get_cpu_var(netdev_rx_stat).dropped++;
-
local_irq_restore(flags);
-
-
kfree_skb(skb);
-
return NET_RX_DROP;
-
}
inet_recvmsg
-
int inet_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
-
size_t size, int flags)
-
{
-
struct sock *sk = sock->sk;
-
int addr_len = 0;
-
int err;
-
-
inet_rps_record_flow(sk);//设置HASH表
-
-
err = sk->sk_prot->recvmsg(iocb, sk, msg, size, flags & MSG_DONTWAIT,
-
flags & ~MSG_DONTWAIT, &addr_len);
-
if (err >= 0)
-
msg->msg_namelen = addr_len;
-
return err;
-
}
这个函数主要是得到全局的rps_sock_flow_table,然后调用rps_record_sock_flow来对rps_sock_flow_table进行设置,这里会将socket的sk_rxhash传递进去当作hash的索引,而这个sk_rxhash其实就是skb里面的rxhash,skb的rxhash就是rps中设置的hash值,这个值是根据四元组进行hash的。这里用这个当索引一个是为了相同的socket都能落入一个index。而且下面的软中断上下文也比较容易存取这个hash表
inet_rps_record_flow
-
static inline void inet_rps_record_flow(struct sock *sk)
-
{
-
struct rps_sock_flow_table *sock_flow_table;
-
-
rcu_read_lock();
-
sock_flow_table = rcu_dereference(rps_sock_flow_table);
-
rps_record_sock_flow(sock_flow_table, inet_sk_rxhash(sk));
-
rcu_read_unlock();
-
}
rps_record_sock_flow
-
static inline void rps_record_sock_flow(struct rps_sock_flow_table *table,
-
u32 hash)
-
{
-
if (table && hash) {
-
/*获取索引*/
-
unsigned int cpu, index = hash & table->mask;
-
-
/* We only give a hint, preemption can change cpu under us 获取CPU */
-
cpu = raw_smp_processor_id();
-
/*保存对应的cpu,如果等于当前cpu,则说明已经设置过了*/
-
if (table->ents[index] != cpu)
-
table->ents[index] = cpu;
-
}
-
}
图:内核代码流程
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