@@ -252,14 +252,7 @@ struct netdev_hw_addr_list {
netdev_hw_addr_list_for_each(ha, &(dev)->mc)
struct hh_cache {
- atomic_t hh_refcnt; /* number of users */
-/*
- * We want hh_output, hh_len, hh_lock and hh_data be a in a separate
- * cache line on SMP.
- * They are mostly read, but hh_refcnt may be changed quite frequently,
- * incurring cache line ping pongs.
- */
- u16 hh_len ____cacheline_aligned_in_smp;
+ u16 hh_len;
u16 __pad;
int (*hh_output)(struct sk_buff *skb);
seqlock_t hh_lock;
@@ -273,12 +266,6 @@ struct hh_cache {
unsigned long hh_data[HH_DATA_ALIGN(LL_MAX_HEADER) / sizeof(long)];
};
-static inline void hh_cache_put(struct hh_cache *hh)
-{
- if (atomic_dec_and_test(&hh->hh_refcnt))
- kfree(hh);
-}
-
/* Reserve HH_DATA_MOD byte aligned hard_header_len, but at least that much.
* Alternative is:
* dev->hard_header_len ? (dev->hard_header_len +
@@ -38,7 +38,6 @@ struct dst_entry {
unsigned long expires;
struct dst_entry *path;
struct neighbour *neighbour;
- struct hh_cache *hh;
#ifdef CONFIG_XFRM
struct xfrm_state *xfrm;
#else
@@ -47,6 +46,14 @@ struct dst_entry {
int (*input)(struct sk_buff*);
int (*output)(struct sk_buff*);
+ int flags;
+#define DST_HOST 0x0001
+#define DST_NOXFRM 0x0002
+#define DST_NOPOLICY 0x0004
+#define DST_NOHASH 0x0008
+#define DST_NOCACHE 0x0010
+#define DST_NOCOUNT 0x0020
+
short error;
short obsolete;
unsigned short header_len; /* more space at head required */
@@ -62,7 +69,7 @@ struct dst_entry {
* (L1_CACHE_SIZE would be too much)
*/
#ifdef CONFIG_64BIT
- long __pad_to_align_refcnt[1];
+ long __pad_to_align_refcnt[2];
#endif
/*
* __refcnt wants to be on a different cache line from
@@ -71,13 +78,6 @@ struct dst_entry {
atomic_t __refcnt; /* client references */
int __use;
unsigned long lastuse;
- int flags;
-#define DST_HOST 0x0001
-#define DST_NOXFRM 0x0002
-#define DST_NOPOLICY 0x0004
-#define DST_NOHASH 0x0008
-#define DST_NOCACHE 0x0010
-#define DST_NOCOUNT 0x0020
union {
struct dst_entry *next;
struct rtable __rcu *rt_next;
@@ -108,7 +108,7 @@ struct neighbour {
__u8 dead;
seqlock_t ha_lock;
unsigned char ha[ALIGN(MAX_ADDR_LEN, sizeof(unsigned long))];
- struct hh_cache *hh;
+ struct hh_cache hh;
int (*output)(struct sk_buff *skb);
const struct neigh_ops *ops;
struct rcu_head rcu;
@@ -343,14 +343,16 @@ static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
{
struct nf_bridge_info *nf_bridge = skb->nf_bridge;
+ struct neighbour *neigh;
struct dst_entry *dst;
skb->dev = bridge_parent(skb->dev);
if (!skb->dev)
goto free_skb;
dst = skb_dst(skb);
- if (dst->hh) {
- neigh_hh_bridge(dst->hh, skb);
+ neigh = dst->neighbour;
+ if (neigh->hh.hh_len) {
+ neigh_hh_bridge(&neigh->hh, skb);
skb->dev = nf_bridge->physindev;
return br_handle_frame_finish(skb);
} else if (dst->neighbour) {
@@ -172,7 +172,6 @@ void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
dst->expires = 0UL;
dst->path = dst;
dst->neighbour = NULL;
- dst->hh = NULL;
#ifdef CONFIG_XFRM
dst->xfrm = NULL;
#endif
@@ -226,19 +225,13 @@ struct dst_entry *dst_destroy(struct dst_entry * dst)
{
struct dst_entry *child;
struct neighbour *neigh;
- struct hh_cache *hh;
smp_rmb();
again:
neigh = dst->neighbour;
- hh = dst->hh;
child = dst->child;
- dst->hh = NULL;
- if (hh)
- hh_cache_put(hh);
-
if (neigh) {
dst->neighbour = NULL;
neigh_release(neigh);
@@ -297,6 +297,7 @@ static struct neighbour *neigh_alloc(struct neigh_table *tbl)
n->updated = n->used = now;
n->nud_state = NUD_NONE;
n->output = neigh_blackhole;
+ seqlock_init(&n->hh.hh_lock);
n->parms = neigh_parms_clone(&tbl->parms);
setup_timer(&n->timer, neigh_timer_handler, (unsigned long)n);
@@ -702,14 +703,11 @@ void neigh_destroy(struct neighbour *neigh)
if (neigh_del_timer(neigh))
printk(KERN_WARNING "Impossible event.\n");
- hh = neigh->hh;
- if (hh) {
- neigh->hh = NULL;
-
+ hh = &neigh->hh;
+ if (hh->hh_len) {
write_seqlock_bh(&hh->hh_lock);
hh->hh_output = neigh_blackhole;
write_sequnlock_bh(&hh->hh_lock);
- hh_cache_put(hh);
}
skb_queue_purge(&neigh->arp_queue);
@@ -737,8 +735,8 @@ static void neigh_suspect(struct neighbour *neigh)
neigh->output = neigh->ops->output;
- hh = neigh->hh;
- if (hh)
+ hh = &neigh->hh;
+ if (hh->hh_len)
hh->hh_output = neigh->ops->output;
}
@@ -755,8 +753,8 @@ static void neigh_connect(struct neighbour *neigh)
neigh->output = neigh->ops->connected_output;
- hh = neigh->hh;
- if (hh)
+ hh = &neigh->hh;
+ if (hh->hh_len)
hh->hh_output = neigh->ops->hh_output;
}
@@ -1017,7 +1015,7 @@ out_unlock_bh:
}
EXPORT_SYMBOL(__neigh_event_send);
-static void neigh_update_hhs(const struct neighbour *neigh)
+static void neigh_update_hhs(struct neighbour *neigh)
{
struct hh_cache *hh;
void (*update)(struct hh_cache*, const struct net_device*, const unsigned char *)
@@ -1027,8 +1025,8 @@ static void neigh_update_hhs(const struct neighbour *neigh)
update = neigh->dev->header_ops->cache_update;
if (update) {
- hh = neigh->hh;
- if (hh) {
+ hh = &neigh->hh;
+ if (hh->hh_len) {
write_seqlock_bh(&hh->hh_lock);
update(hh, neigh->dev, neigh->ha);
write_sequnlock_bh(&hh->hh_lock);
@@ -1214,62 +1212,29 @@ struct neighbour *neigh_event_ns(struct neigh_table *tbl,
}
EXPORT_SYMBOL(neigh_event_ns);
-static inline bool neigh_hh_lookup(struct neighbour *n, struct dst_entry *dst)
-{
- struct hh_cache *hh;
-
- smp_rmb(); /* paired with smp_wmb() in neigh_hh_init() */
- hh = n->hh;
- if (hh) {
- atomic_inc(&hh->hh_refcnt);
- if (unlikely(cmpxchg(&dst->hh, NULL, hh) != NULL))
- hh_cache_put(hh);
- return true;
- }
- return false;
-}
-
/* called with read_lock_bh(&n->lock); */
-static void neigh_hh_init(struct neighbour *n, struct dst_entry *dst,
- __be16 protocol)
+static void neigh_hh_init(struct neighbour *n, struct dst_entry *dst)
{
- struct hh_cache *hh;
struct net_device *dev = dst->dev;
-
- if (likely(neigh_hh_lookup(n, dst)))
- return;
-
- /* slow path */
- hh = kzalloc(sizeof(*hh), GFP_ATOMIC);
- if (!hh)
- return;
-
- seqlock_init(&hh->hh_lock);
- atomic_set(&hh->hh_refcnt, 2);
-
- if (dev->header_ops->cache(n, hh, protocol)) {
- kfree(hh);
- return;
- }
+ __be16 prot = dst->ops->protocol;
+ struct hh_cache *hh = &n->hh;
write_lock_bh(&n->lock);
- /* must check if another thread already did the insert */
- if (neigh_hh_lookup(n, dst)) {
- kfree(hh);
+ /* Only one thread can come in here and initialize the
+ * hh_cache entry.
+ */
+ if (hh->hh_len)
+ goto end;
+
+ if (dev->header_ops->cache(n, hh, prot))
goto end;
- }
if (n->nud_state & NUD_CONNECTED)
hh->hh_output = n->ops->hh_output;
else
hh->hh_output = n->ops->output;
- smp_wmb(); /* paired with smp_rmb() in neigh_hh_lookup() */
- n->hh = hh;
-
- if (unlikely(cmpxchg(&dst->hh, NULL, hh) != NULL))
- hh_cache_put(hh);
end:
write_unlock_bh(&n->lock);
}
@@ -1312,10 +1277,8 @@ int neigh_resolve_output(struct sk_buff *skb)
struct net_device *dev = neigh->dev;
unsigned int seq;
- if (dev->header_ops->cache &&
- !dst->hh &&
- !(dst->flags & DST_NOCACHE))
- neigh_hh_init(neigh, dst, dst->ops->protocol);
+ if (dev->header_ops->cache && !neigh->hh.hh_len)
+ neigh_hh_init(neigh, dst);
do {
seq = read_seqbegin(&neigh->ha_lock);
@@ -182,6 +182,7 @@ static inline int ip_finish_output2(struct sk_buff *skb)
struct rtable *rt = (struct rtable *)dst;
struct net_device *dev = dst->dev;
unsigned int hh_len = LL_RESERVED_SPACE(dev);
+ struct neighbour *neigh;
if (rt->rt_type == RTN_MULTICAST) {
IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
@@ -203,11 +204,14 @@ static inline int ip_finish_output2(struct sk_buff *skb)
skb = skb2;
}
- if (dst->hh)
- return neigh_hh_output(dst->hh, skb);
- else if (dst->neighbour)
- return dst->neighbour->output(skb);
-
+ neigh = dst->neighbour;
+ if (neigh) {
+ struct hh_cache *hh = &neigh->hh;
+ if (hh->hh_len)
+ return neigh_hh_output(hh, skb);
+ else
+ return dst->neighbour->output(skb);
+ }
if (net_ratelimit())
printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
kfree_skb(skb);
@@ -426,9 +426,10 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v)
(int)((dst_metric(&r->dst, RTAX_RTT) >> 3) +
dst_metric(&r->dst, RTAX_RTTVAR)),
r->rt_key_tos,
- r->dst.hh ? atomic_read(&r->dst.hh->hh_refcnt) : -1,
- r->dst.hh ? (r->dst.hh->hh_output ==
- dev_queue_xmit) : 0,
+ -1,
+ (r->dst.neighbour ?
+ (r->dst.neighbour->hh.hh_output ==
+ dev_queue_xmit) : 0),
r->rt_spec_dst, &len);
seq_printf(seq, "%*s\n", 127 - len, "");
@@ -100,6 +100,7 @@ static int ip6_finish_output2(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
struct net_device *dev = dst->dev;
+ struct neighbour *neigh;
skb->protocol = htons(ETH_P_IPV6);
skb->dev = dev;
@@ -134,11 +135,14 @@ static int ip6_finish_output2(struct sk_buff *skb)
skb->len);
}
- if (dst->hh)
- return neigh_hh_output(dst->hh, skb);
- else if (dst->neighbour)
- return dst->neighbour->output(skb);
-
+ neigh = dst->neighbour;
+ if (neigh) {
+ struct hh_cache *hh = &neigh->hh;
+ if (hh->hh_len)
+ return neigh_hh_output(hh, skb);
+ else
+ return dst->neighbour->output(skb);
+ }
IP6_INC_STATS_BH(dev_net(dst->dev),
ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
kfree_skb(skb);
Now that there is a one-to-one correspondance between neighbour and hh_cache entries, we no longer need: 1) dynamic allocation 2) attachment to dst->hh 3) refcounting Initialization of the hh_cache entry is indicated by hh_len being non-zero, and such initialization is always done with the neighbour's lock held as a writer. Signed-off-by: David S. Miller <davem@davemloft.net> -- This passes a bunch of basic testing I've done, and shaves a few seconds off of the udpflood test. Eric, I tried to do something reasonable with the resulting dst_entry layout wrt. the 64-byte alignment thing. I'm open to suggestions. And also notice how we don't need that DST_NOCACHE test any more, since we now don't do atomics or modify dst_entry state just to setup the hh_cache entry. I hadn't really thought about this aspect of DST_NOCACHE before, but it means that with the routing cache removal patches applied, HH caching was completely disabled :-/ Well, at least now that will be fixed :)) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html