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Message-Id: <1405481312-7790-3-git-send-email-drheld@google.com>
Date: Tue, 15 Jul 2014 23:28:32 -0400
From: David Held <drheld@...gle.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, eric.dumazet@...il.com, willemb@...gle.com,
David Held <drheld@...gle.com>
Subject: [PATCH net-next v3 2/2] udp: Use hash2 for long hash1 chains in __udp*_lib_mcast_deliver.
Many multicast sources can have the same port which can result in a very
large list when hashing by port only. Hash by address and port instead
if this is the case. This makes multicast more similar to unicast.
On a 24-core machine receiving from 500 multicast sockets on the same
port, before this patch 80% of system CPU was used up by spin locking
and only ~25% of packets were successfully delivered.
With this patch, all packets are delivered and kernel overhead is ~8%
system CPU on spinlocks.
Signed-off-by: David Held <drheld@...gle.com>
---
include/net/sock.h | 14 ++++++++++++++
net/ipv4/udp.c | 31 +++++++++++++++++++++----------
net/ipv6/udp.c | 30 ++++++++++++++++++++----------
3 files changed, 55 insertions(+), 20 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index cb84b2f..6734cab 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -660,6 +660,20 @@ static inline void sk_add_bind_node(struct sock *sk,
#define sk_for_each_bound(__sk, list) \
hlist_for_each_entry(__sk, list, sk_bind_node)
+/**
+ * sk_nulls_for_each_entry_offset - iterate over a list at a given struct offset
+ * @tpos: the type * to use as a loop cursor.
+ * @pos: the &struct hlist_node to use as a loop cursor.
+ * @head: the head for your list.
+ * @offset: offset of hlist_node within the struct.
+ *
+ */
+#define sk_nulls_for_each_entry_offset(tpos, pos, head, offset) \
+ for (pos = (head)->first; \
+ (!is_a_nulls(pos)) && \
+ ({ tpos = (typeof(*tpos) *)((void *)pos - offset); 1;}); \
+ pos = pos->next)
+
static inline struct user_namespace *sk_user_ns(struct sock *sk)
{
/* Careful only use this in a context where these parameters
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 1347a24..21ca57d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1616,6 +1616,8 @@ static void flush_stack(struct sock **stack, unsigned int count,
if (skb1 && udp_queue_rcv_skb(sk, skb1) <= 0)
skb1 = NULL;
+
+ sock_put(sk);
}
if (unlikely(skb1))
kfree_skb(skb1);
@@ -1648,10 +1650,20 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
unsigned short hnum = ntohs(uh->dest);
struct udp_hslot *hslot = udp_hashslot(udptable, net, hnum);
int dif = skb->dev->ifindex;
- unsigned int i, count = 0;
+ unsigned int count = 0, offset = offsetof(typeof(*sk), sk_nulls_node);
+ unsigned int hash2 = 0, hash2_any = 0, use_hash2 = (hslot->count > 10);
+
+ if (use_hash2) {
+ hash2_any = udp4_portaddr_hash(net, htonl(INADDR_ANY), hnum) &
+ udp_table.mask;
+ hash2 = udp4_portaddr_hash(net, daddr, hnum) & udp_table.mask;
+start_lookup:
+ hslot = &udp_table.hash2[hash2];
+ offset = offsetof(typeof(*sk), __sk_common.skc_portaddr_node);
+ }
spin_lock(&hslot->lock);
- sk_nulls_for_each(sk, node, &hslot->head) {
+ sk_nulls_for_each_entry_offset(sk, node, &hslot->head, offset) {
if (__udp_is_mcast_sock(net, sk,
uh->dest, daddr,
uh->source, saddr,
@@ -1661,24 +1673,23 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
count = 0;
}
stack[count++] = sk;
+ sock_hold(sk);
}
}
- /*
- * before releasing chain lock, we must take a reference on sockets
- */
- for (i = 0; i < count; i++)
- sock_hold(stack[i]);
spin_unlock(&hslot->lock);
+ /* Also lookup *:port if we are using hash2 and haven't done so yet. */
+ if (use_hash2 && hash2 != hash2_any) {
+ hash2 = hash2_any;
+ goto start_lookup;
+ }
+
/*
* do the slow work with no lock held
*/
if (count) {
flush_stack(stack, count, skb, count - 1);
-
- for (i = 0; i < count; i++)
- sock_put(stack[i]);
} else {
kfree_skb(skb);
}
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 6bcfbb8..21f4fe9 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -741,6 +741,7 @@ static void flush_stack(struct sock **stack, unsigned int count,
if (skb1 && udpv6_queue_rcv_skb(sk, skb1) <= 0)
skb1 = NULL;
+ sock_put(sk);
}
if (unlikely(skb1))
kfree_skb(skb1);
@@ -770,10 +771,20 @@ static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
unsigned short hnum = ntohs(uh->dest);
struct udp_hslot *hslot = udp_hashslot(udptable, net, hnum);
int dif = inet6_iif(skb);
- unsigned int i, count = 0;
+ unsigned int count = 0, offset = offsetof(typeof(*sk), sk_nulls_node);
+ unsigned int hash2 = 0, hash2_any = 0, use_hash2 = (hslot->count > 10);
+
+ if (use_hash2) {
+ hash2_any = udp6_portaddr_hash(net, &in6addr_any, hnum) &
+ udp_table.mask;
+ hash2 = udp6_portaddr_hash(net, daddr, hnum) & udp_table.mask;
+start_lookup:
+ hslot = &udp_table.hash2[hash2];
+ offset = offsetof(typeof(*sk), __sk_common.skc_portaddr_node);
+ }
spin_lock(&hslot->lock);
- sk_nulls_for_each(sk, node, &hslot->head) {
+ sk_nulls_for_each_entry_offset(sk, node, &hslot->head, offset) {
if (__udp_v6_is_mcast_sock(net, sk,
uh->dest, daddr,
uh->source, saddr,
@@ -787,21 +798,20 @@ static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
count = 0;
}
stack[count++] = sk;
+ sock_hold(sk);
}
}
- /*
- * before releasing the lock, we must take reference on sockets
- */
- for (i = 0; i < count; i++)
- sock_hold(stack[i]);
spin_unlock(&hslot->lock);
+ /* Also lookup *:port if we are using hash2 and haven't done so yet. */
+ if (use_hash2 && hash2 != hash2_any) {
+ hash2 = hash2_any;
+ goto start_lookup;
+ }
+
if (count) {
flush_stack(stack, count, skb, count - 1);
-
- for (i = 0; i < count; i++)
- sock_put(stack[i]);
} else {
kfree_skb(skb);
}
--
2.0.0.526.g5318336
--
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