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Message-ID: <4AF454B7.6050103@gmail.com>
Date: Fri, 06 Nov 2009 17:54:15 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: Lucian Adrian Grijincu <lgrijincu@...acom.com>
CC: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
opurdila@...acom.com
Subject: Re: [PATCH net-next-2.6] udp: Optimise multicast reception
Lucian Adrian Grijincu a écrit :
> În data de Vin 06 Noi 2009 17:59:51 ați scris:
>> +static void flush_stack(struct sock **stack, unsigned int count,
>> + struct sk_buff *skb, unsigned int final)
>> +{
>> + unsigned int i;
>> + struct sk_buff *skb1 = NULL;
>> +
>> + for (i = 0; i < count; i++) {
>> + if (likely(skb1 == NULL))
>> + skb1 = (i == final) ? skb : skb_clone(skb, GFP_ATOMIC);
>> +
>> + if (skb1 && udp_queue_rcv_skb(stack[i], skb1) <= 0)
>> + skb1 = NULL;
>> + }
>> + if (skb1)
>> + consume_skb(skb1);
>> +}
>
> consume_skb() assumes the skb was successfuly transmitted.
>
> free_skb() does the same thing, but assumes that the frame is being dropped
> after a failure and notes that.
>
> In your code, if (count == 0) you:
> * fail to remove the original skb (memory leak),
> * simply consume the last dropped skb, without noting the droping failure.
>
> I fixed these in the attached (untested) patch.
>
> One last issue: you silently ignore dropped failures (skb1 is reused in case
> of a failure).
>
> If this tracing must record all failures, I'd add an
> trace_kfree_skb(skb1, __builtin_return_address(0));
> if udp_queue_rcv_skb() fails.
>
> Other than this, nicely done!
>
Thanks !
Note, free_skb() doesnt exist ;)
And we should not call consume_skb() in this path.
I made the if (count == 0) done at the end of __udp4_lib_mcast_deliver()
[PATCH net-next-2.6] udp: Optimise multicast reception
UDP multicast rx path is a bit complex and can hold a spinlock
for a long time.
Using a small (32 or 64 entries) stack of socket pointers can help
to perform expensive operations (skb_clone(), udp_queue_rcv_skb())
outside of the lock, in most cases.
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Lucian Adrian Grijincu <lgrijincu@...acom.com>
---
net/ipv4/udp.c | 76 ++++++++++++++++++++++++++++++-----------------
1 files changed, 50 insertions(+), 26 deletions(-)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d5e75e9..45c73b1 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1190,49 +1190,73 @@ drop:
return -1;
}
+
+static void flush_stack(struct sock **stack, unsigned int count,
+ struct sk_buff *skb, unsigned int final)
+{
+ unsigned int i;
+ struct sk_buff *skb1 = NULL;
+
+ for (i = 0; i < count; i++) {
+ if (likely(skb1 == NULL))
+ skb1 = (i == final) ? skb : skb_clone(skb, GFP_ATOMIC);
+
+ if (skb1 && udp_queue_rcv_skb(stack[i], skb1) <= 0)
+ skb1 = NULL;
+ }
+ if (unlikely(skb1))
+ kfree_skb(skb1);
+}
+
/*
* Multicasts and broadcasts go to each listener.
*
- * Note: called only from the BH handler context,
- * so we don't need to lock the hashes.
+ * Note: called only from the BH handler context.
*/
static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
struct udphdr *uh,
__be32 saddr, __be32 daddr,
struct udp_table *udptable)
{
- struct sock *sk;
+ struct sock *sk, *stack[256 / sizeof(struct sock *)];
struct udp_hslot *hslot = udp_hashslot(udptable, net, ntohs(uh->dest));
int dif;
+ unsigned int i, count = 0;
spin_lock(&hslot->lock);
sk = sk_nulls_head(&hslot->head);
dif = skb->dev->ifindex;
sk = udp_v4_mcast_next(net, sk, uh->dest, daddr, uh->source, saddr, dif);
- if (sk) {
- struct sock *sknext = NULL;
-
- do {
- struct sk_buff *skb1 = skb;
-
- sknext = udp_v4_mcast_next(net, sk_nulls_next(sk), uh->dest,
- daddr, uh->source, saddr,
- dif);
- if (sknext)
- skb1 = skb_clone(skb, GFP_ATOMIC);
-
- if (skb1) {
- int ret = udp_queue_rcv_skb(sk, skb1);
- if (ret > 0)
- /* we should probably re-process instead
- * of dropping packets here. */
- kfree_skb(skb1);
- }
- sk = sknext;
- } while (sknext);
- } else
- consume_skb(skb);
+ while (sk) {
+ stack[count++] = sk;
+ sk = udp_v4_mcast_next(net, sk_nulls_next(sk), uh->dest,
+ daddr, uh->source, saddr, dif);
+ if (unlikely(count == ARRAY_SIZE(stack))) {
+ if (!sk)
+ break;
+ flush_stack(stack, count, skb, ~0);
+ count = 0;
+ }
+ }
+ /*
+ * 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);
+
+ /*
+ * 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);
+ }
return 0;
}
--
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