From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Herbert Subject: Re: [PATCH v4 1/1] rps: core implementation Date: Wed, 6 Jan 2010 14:54:02 -0800 Message-ID: <65634d661001061454v389d311fjb245de21e0ab8092@mail.gmail.com> References: <65634d660911201528k5a07135el471b65fff9dd7c9d@mail.gmail.com> <20091120154046.67252d23@nehalam> <65634d660912171304p751e1698mbc9de50dade4317d@mail.gmail.com> <65634d661001051732qd64e79dt37e6247f8b0dc863@mail.gmail.com> <4B44258C.2050302@gmail.com> <4B44D89B.8070006@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: David Miller , Linux Netdev List To: Eric Dumazet Return-path: Received: from smtp-out.google.com ([216.239.33.17]:1028 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756501Ab0AFWyL (ORCPT ); Wed, 6 Jan 2010 17:54:11 -0500 Received: from kpbe19.cbf.corp.google.com (kpbe19.cbf.corp.google.com [172.25.105.83]) by smtp-out.google.com with ESMTP id o06Ms4Ef001365 for ; Wed, 6 Jan 2010 22:54:05 GMT Received: from pxi4 (pxi4.prod.google.com [10.243.27.4]) by kpbe19.cbf.corp.google.com with ESMTP id o06Ms3O8027194 for ; Wed, 6 Jan 2010 14:54:03 -0800 Received: by pxi4 with SMTP id 4so802705pxi.33 for ; Wed, 06 Jan 2010 14:54:03 -0800 (PST) In-Reply-To: <4B44D89B.8070006@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Eric, thanks again for your good comments. Here is my patch that addresses them, including: - Added softnet counter for number of rps softirq triggers - Force at least one map entry for devices with no napi's - Replace rcu_read_lock_bh with rtnl_lock when assigning dev_rps_maps pointer in store_rps_cpus - Replaced get_cpu_var with __get_cpu_var in enqueue_to_backlog (fix unmatched preempt_disable) - Restored calling napi_receive_skb in napi_gro_complete, napi_skb_finish, and napi_frags_finish. This fixes the problem with GRO that I had described previously. Patch should now work with drivers that call napi_gro_receive (verified with e1000e) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 97873e3..078cb55 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -222,6 +222,7 @@ struct netif_rx_stats { unsigned dropped; unsigned time_squeeze; unsigned cpu_collision; + unsigned received_rps; }; DECLARE_PER_CPU(struct netif_rx_stats, netdev_rx_stat); @@ -676,6 +677,29 @@ struct net_device_ops { }; /* + * Structure for Receive Packet Steering. Length of map and array of CPU ID's. + */ +struct rps_map { + int len; + u16 map[0]; +}; + +/* + * Structure that contains the rps maps for various NAPI instances of a device. + */ +struct dev_rps_maps { + int num_maps; + struct rcu_head rcu; + struct rps_map maps[0]; +}; + +/* Bound number of CPUs that can be in an rps map */ +#define MAX_RPS_CPUS (num_possible_cpus() < 256 ? num_possible_cpus() : 256) + +/* Maximum size of RPS map (for allocation) */ +#define RPS_MAP_SIZE (sizeof(struct rps_map) + (MAX_RPS_CPUS * sizeof(u16))) + +/* * The DEVICE structure. * Actually, this whole structure is a big mistake. It mixes I/O * data with strictly "high-level" data, and it has to know about @@ -861,6 +885,9 @@ struct net_device { struct netdev_queue rx_queue; + struct dev_rps_maps *dev_rps_maps; /* Per-NAPI maps for + receive packet steeing */ + struct netdev_queue *_tx ____cacheline_aligned_in_smp; /* Number of TX queues allocated at alloc_netdev_mq() time */ @@ -1274,10 +1301,12 @@ static inline int unregister_gifconf(unsigned int family) */ struct softnet_data { struct Qdisc *output_queue; - struct sk_buff_head input_pkt_queue; struct list_head poll_list; struct sk_buff *completion_queue; + /* Elements below can be accessed between CPUs for RPS */ + struct call_single_data csd ____cacheline_aligned_in_smp; + struct sk_buff_head input_pkt_queue; struct napi_struct backlog; }; diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 63f4742..f188301 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -267,6 +267,7 @@ typedef unsigned char *sk_buff_data_t; * @mac_header: Link layer header * @_skb_dst: destination entry * @sp: the security path, used for xfrm + * @rxhash: the packet hash computed on receive * @cb: Control buffer. Free for use by every layer. Put private vars here * @len: Length of actual data * @data_len: Data length @@ -323,6 +324,8 @@ struct sk_buff { #ifdef CONFIG_XFRM struct sec_path *sp; #endif + __u32 rxhash; + /* * This is the control buffer. It is free to use for every * layer. Please put your private variables there. If you diff --git a/net/core/dev.c b/net/core/dev.c index 9977288..732efe3 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1834,7 +1834,7 @@ out_kfree_skb: return rc; } -static u32 skb_tx_hashrnd; +static u32 hashrnd __read_mostly; u16 skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb) { @@ -1852,7 +1852,7 @@ u16 skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb) else hash = skb->protocol; - hash = jhash_1word(hash, skb_tx_hashrnd); + hash = jhash_1word(hash, hashrnd); return (u16) (((u64) hash * dev->real_num_tx_queues) >> 32); } @@ -2073,6 +2073,149 @@ int weight_p __read_mostly = 64; /* old backlog weight */ DEFINE_PER_CPU(struct netif_rx_stats, netdev_rx_stat) = { 0, }; +/* + * get_rps_cpu is called from netif_receive_skb and returns the target + * CPU from the RPS map of the receiving NAPI instance for a given skb. + */ +static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb) +{ + u32 addr1, addr2, ports; + struct ipv6hdr *ip6; + struct iphdr *ip; + u32 ihl; + u8 ip_proto; + int cpu = -1; + struct dev_rps_maps *drmap; + struct rps_map *map = NULL; + u16 index; + + rcu_read_lock(); + + drmap = rcu_dereference(dev->dev_rps_maps); + if (!drmap) + goto done; + + index = skb_get_rx_queue(skb); + if (index >= drmap->num_maps) + index = 0; + + map = (struct rps_map *) + ((void *)drmap->maps + (RPS_MAP_SIZE * index)); + if (!map->len) + goto done; + + if (skb->rxhash) + goto got_hash; /* Skip hash computation on packet header */ + + switch (skb->protocol) { + case __constant_htons(ETH_P_IP): + if (!pskb_may_pull(skb, sizeof(*ip))) + goto done; + + ip = (struct iphdr *) skb->data; + ip_proto = ip->protocol; + addr1 = ip->saddr; + addr2 = ip->daddr; + ihl = ip->ihl; + break; + case __constant_htons(ETH_P_IPV6): + if (!pskb_may_pull(skb, sizeof(*ip6))) + goto done; + + ip6 = (struct ipv6hdr *) skb->data; + ip_proto = ip6->nexthdr; + addr1 = ip6->saddr.s6_addr32[3]; + addr2 = ip6->daddr.s6_addr32[3]; + 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))); + break; + + default: + break; + } + + skb->rxhash = jhash_3words(addr1, addr2, ports, hashrnd); + if (!skb->rxhash) + skb->rxhash = 1; + +got_hash: + cpu = map->map[((u64) skb->rxhash * map->len) >> 32]; + + if (!cpu_online(cpu)) + cpu = -1; +done: + rcu_read_unlock(); + return cpu; +} + +static DEFINE_PER_CPU(cpumask_t, rps_remote_softirq_cpus); + +/* Called from hardirq (IPI) context */ +static void trigger_softirq(void *data) +{ + struct softnet_data *queue = data; + __napi_schedule(&queue->backlog); + __get_cpu_var(netdev_rx_stat).received_rps++; +} + +/* + * enqueue_to_backlog is called to queue an skb to a per CPU backlog + * queue (may be a remote CPU queue). + */ +static int enqueue_to_backlog(struct sk_buff *skb, int cpu) +{ + struct softnet_data *queue; + unsigned long flags; + + 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: + __skb_queue_tail(&queue->input_pkt_queue, skb); + spin_unlock_irqrestore(&queue->input_pkt_queue.lock, + flags); + return NET_RX_SUCCESS; + } + + /* Schedule NAPI for backlog device */ + if (napi_schedule_prep(&queue->backlog)) { + if (cpu != smp_processor_id()) { + cpu_set(cpu, + __get_cpu_var(rps_remote_softirq_cpus)); + __raise_softirq_irqoff(NET_RX_SOFTIRQ); + } else + __napi_schedule(&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; +} /** * netif_rx - post buffer to the network code @@ -2091,8 +2234,7 @@ DEFINE_PER_CPU(struct netif_rx_stats, netdev_rx_stat) = { 0, }; int netif_rx(struct sk_buff *skb) { - struct softnet_data *queue; - unsigned long flags; + int cpu; /* if netpoll wants it, pretend we never saw it */ if (netpoll_rx(skb)) @@ -2101,31 +2243,12 @@ int netif_rx(struct sk_buff *skb) if (!skb->tstamp.tv64) net_timestamp(skb); - /* - * The code is rearranged so that the path is the most - * short when CPU is congested, but is still operating. - */ - local_irq_save(flags); - queue = &__get_cpu_var(softnet_data); - - __get_cpu_var(netdev_rx_stat).total++; - if (queue->input_pkt_queue.qlen <= netdev_max_backlog) { - if (queue->input_pkt_queue.qlen) { -enqueue: - __skb_queue_tail(&queue->input_pkt_queue, skb); - local_irq_restore(flags); - return NET_RX_SUCCESS; - } - - napi_schedule(&queue->backlog); - goto enqueue; - } - __get_cpu_var(netdev_rx_stat).dropped++; - local_irq_restore(flags); + cpu = get_rps_cpu(skb->dev, skb); + if (cpu < 0) + cpu = smp_processor_id(); - kfree_skb(skb); - return NET_RX_DROP; + return enqueue_to_backlog(skb, cpu); } EXPORT_SYMBOL(netif_rx); @@ -2363,10 +2486,10 @@ void netif_nit_deliver(struct sk_buff *skb) } /** - * netif_receive_skb - process receive buffer from network + * __netif_receive_skb - process receive buffer from network * @skb: buffer to process * - * netif_receive_skb() is the main receive data processing function. + * __netif__napireceive_skb() is the main receive data processing function. * It always succeeds. The buffer may be dropped during processing * for congestion control or by the protocol layers. * @@ -2377,7 +2500,8 @@ void netif_nit_deliver(struct sk_buff *skb) * NET_RX_SUCCESS: no congestion * NET_RX_DROP: packet was dropped */ -int netif_receive_skb(struct sk_buff *skb) + +int __netif_receive_skb(struct sk_buff *skb) { struct packet_type *ptype, *pt_prev; struct net_device *orig_dev; @@ -2475,6 +2599,16 @@ out: } EXPORT_SYMBOL(netif_receive_skb); +int netif_receive_skb(struct sk_buff *skb) +{ + int cpu = get_rps_cpu(skb->dev, skb); + + if (cpu < 0) + return __netif_receive_skb(skb); + else + return enqueue_to_backlog(skb, cpu); +} + /* Network device is going away, flush any packets still pending */ static void flush_backlog(void *arg) { @@ -2799,16 +2933,16 @@ static int process_backlog(struct napi_struct *napi, int quota) do { struct sk_buff *skb; - local_irq_disable(); + spin_lock_irq(&queue->input_pkt_queue.lock); skb = __skb_dequeue(&queue->input_pkt_queue); if (!skb) { __napi_complete(napi); - local_irq_enable(); + spin_unlock_irq(&queue->input_pkt_queue.lock); break; } - local_irq_enable(); + spin_unlock_irq(&queue->input_pkt_queue.lock); - netif_receive_skb(skb); + __netif_receive_skb(skb); } while (++work < quota && jiffies == start_time); return work; @@ -2897,6 +3031,21 @@ void netif_napi_del(struct napi_struct *napi) } EXPORT_SYMBOL(netif_napi_del); +/* + * net_rps_action sends any pending IPI's for rps. This is only called from + * softirq and interrupts must be enabled. + */ +static void net_rps_action(void) +{ + int cpu; + + /* Send pending IPI's to kick RPS processing on remote cpus. */ + for_each_cpu_mask_nr(cpu, __get_cpu_var(rps_remote_softirq_cpus)) { + struct softnet_data *queue = &per_cpu(softnet_data, cpu); + cpu_clear(cpu, __get_cpu_var(rps_remote_softirq_cpus)); + __smp_call_function_single(cpu, &queue->csd, 0); + } +} static void net_rx_action(struct softirq_action *h) { @@ -2968,6 +3117,8 @@ static void net_rx_action(struct softirq_action *h) out: local_irq_enable(); + net_rps_action(); + #ifdef CONFIG_NET_DMA /* * There may not be any more sk_buffs coming right now, so push @@ -3212,10 +3363,10 @@ static int softnet_seq_show(struct seq_file *seq, void *v) { struct netif_rx_stats *s = v; - seq_printf(seq, "%08x %08x %08x %08x %08x %08x %08x %08x %08x\n", + seq_printf(seq, "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x\n", s->total, s->dropped, s->time_squeeze, 0, 0, 0, 0, 0, /* was fastroute */ - s->cpu_collision); + s->cpu_collision, s->received_rps); return 0; } @@ -5341,6 +5492,8 @@ void free_netdev(struct net_device *dev) /* Flush device addresses */ dev_addr_flush(dev); + kfree(dev->dev_rps_maps); + list_for_each_entry_safe(p, n, &dev->napi_list, dev_list) netif_napi_del(p); @@ -5793,6 +5946,10 @@ static int __init net_dev_init(void) queue->completion_queue = NULL; INIT_LIST_HEAD(&queue->poll_list); + queue->csd.func = trigger_softirq; + queue->csd.info = queue; + queue->csd.flags = 0; + queue->backlog.poll = process_backlog; queue->backlog.weight = weight_p; queue->backlog.gro_list = NULL; @@ -5831,7 +5988,7 @@ subsys_initcall(net_dev_init); static int __init initialize_hashrnd(void) { - get_random_bytes(&skb_tx_hashrnd, sizeof(skb_tx_hashrnd)); + get_random_bytes(&hashrnd, sizeof(hashrnd)); return 0; } diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c index 157645c..4bf4851 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -18,6 +18,9 @@ #include #include +#include +#include + #include "net-sysfs.h" #ifdef CONFIG_SYSFS @@ -253,6 +256,134 @@ static ssize_t store_tx_queue_len(struct device *dev, return netdev_store(dev, attr, buf, len, change_tx_queue_len); } +static char *get_token(const char **cp, size_t *len) +{ + const char *bp = *cp; + char *start; + + while (isspace(*bp)) + bp++; + + start = (char *)bp; + while (!isspace(*bp) && *bp != '\0') + bp++; + + if (start != bp) + *len = bp - start; + else + start = NULL; + + *cp = bp; + return start; +} + +static void dev_map_release(struct rcu_head *rcu) +{ + struct dev_rps_maps *drmap = + container_of(rcu, struct dev_rps_maps, rcu); + + kfree(drmap); +} + +static ssize_t store_rps_cpus(struct device *dev, + struct device_attribute *attr, const char *buf, size_t len) +{ + struct net_device *net = to_net_dev(dev); + struct napi_struct *napi; + cpumask_t mask; + int err, cpu, index, i; + int cnt = 0; + char *token; + const char *cp = buf; + size_t tlen; + struct dev_rps_maps *drmap, *old_drmap; + + if (!capable(CAP_NET_ADMIN)) + return -EPERM; + + cnt = 0; + list_for_each_entry(napi, &net->napi_list, dev_list) + cnt++; + if (cnt == 0) + cnt = 1; /* For devices with no napi instances */ + + drmap = kzalloc(sizeof(struct dev_rps_maps) + + RPS_MAP_SIZE * cnt, GFP_KERNEL); + if (!drmap) + return -ENOMEM; + + drmap->num_maps = cnt; + + cp = buf; + for (index = 0; index < cnt && + (token = get_token(&cp, &tlen)); index++) { + struct rps_map *map = (struct rps_map *) + ((void *)drmap->maps + (RPS_MAP_SIZE * index)); + err = bitmap_parse(token, tlen, cpumask_bits(&mask), + nr_cpumask_bits); + + if (err) { + kfree(drmap); + return err; + } + + cpus_and(mask, mask, cpu_online_map); + i = 0; + for_each_cpu_mask(cpu, mask) { + if (i >= MAX_RPS_CPUS) + break; + map->map[i++] = cpu; + } + map->len = i; + } + + rtnl_lock(); + old_drmap = rcu_dereference(net->dev_rps_maps); + rcu_assign_pointer(net->dev_rps_maps, drmap); + rtnl_unlock(); + + if (old_drmap) + call_rcu(&old_drmap->rcu, dev_map_release); + + return len; +} + +static ssize_t show_rps_cpus(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct net_device *net = to_net_dev(dev); + size_t len = 0; + cpumask_t mask; + int i, j; + struct dev_rps_maps *drmap; + + rcu_read_lock_bh(); + drmap = rcu_dereference(net->dev_rps_maps); + + if (drmap) { + for (j = 0; j < drmap->num_maps; j++) { + struct rps_map *map = (struct rps_map *) + ((void *)drmap->maps + (RPS_MAP_SIZE * j)); + cpus_clear(mask); + for (i = 0; i < map->len; i++) + cpu_set(map->map[i], mask); + + len += cpumask_scnprintf(buf + len, PAGE_SIZE, &mask); + if (PAGE_SIZE - len < 3) { + rcu_read_unlock(); + return -EINVAL; + } + if (j < drmap->num_maps) + len += sprintf(buf + len, " "); + } + } + + rcu_read_unlock_bh(); + + len += sprintf(buf + len, "\n"); + return len; +} + static ssize_t store_ifalias(struct device *dev, struct device_attribute *attr, const char *buf, size_t len) { @@ -309,6 +440,7 @@ static struct device_attribute net_class_attributes[] = { __ATTR(flags, S_IRUGO | S_IWUSR, show_flags, store_flags), __ATTR(tx_queue_len, S_IRUGO | S_IWUSR, show_tx_queue_len, store_tx_queue_len), + __ATTR(rps_cpus, S_IRUGO | S_IWUSR, show_rps_cpus, store_rps_cpus), {} };