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authorEric Dumazet <edumazet@google.com>2013-04-12 11:31:52 +0000
committerDavid S. Miller <davem@davemloft.net>2013-04-12 18:17:06 -0400
commitd6a4a10411764cf1c3a5dad4f06c5ebe5194488b (patch)
tree54d1e4c0c92bc780d9e2f8a822c1c8dc271df70d /net/ipv4/tcp.c
parentd14a489a411937fb9420fe2b05168ee9e1e06c9c (diff)
downloadlinux-stericsson-d6a4a10411764cf1c3a5dad4f06c5ebe5194488b.tar.gz
tcp: GSO should be TSQ friendly
I noticed that TSQ (TCP Small queues) was less effective when TSO is turned off, and GSO is on. If BQL is not enabled, TSQ has then no effect. It turns out the GSO engine frees the original gso_skb at the time the fragments are generated and queued to the NIC. We should instead call the tcp_wfree() destructor for the last fragment, to keep the flow control as intended in TSQ. This effectively limits the number of queued packets on qdisc + NIC layers. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Tom Herbert <therbert@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Nandita Dukkipati <nanditad@google.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp.c')
-rw-r--r--net/ipv4/tcp.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index a96f7b586277..963bda18486f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2885,6 +2885,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
__be32 delta;
unsigned int oldlen;
unsigned int mss;
+ struct sk_buff *gso_skb = skb;
if (!pskb_may_pull(skb, sizeof(*th)))
goto out;
@@ -2953,6 +2954,17 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
th->cwr = 0;
} while (skb->next);
+ /* Following permits TCP Small Queues to work well with GSO :
+ * The callback to TCP stack will be called at the time last frag
+ * is freed at TX completion, and not right now when gso_skb
+ * is freed by GSO engine
+ */
+ if (gso_skb->destructor == tcp_wfree) {
+ swap(gso_skb->sk, skb->sk);
+ swap(gso_skb->destructor, skb->destructor);
+ swap(gso_skb->truesize, skb->truesize);
+ }
+
delta = htonl(oldlen + (skb->tail - skb->transport_header) +
skb->data_len);
th->check = ~csum_fold((__force __wsum)((__force u32)th->check +