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authorEric Dumazet <eric.dumazet@gmail.com>2012-04-10 20:30:48 +0000
committerDavid S. Miller <davem@davemloft.net>2012-04-11 10:11:12 -0400
commita21d45726acacc963d8baddf74607d9b74e2b723 (patch)
tree7cd7e1409ac0242148a0a8117956d08572eb32cf /net/ipv4/tcp_output.c
parent87151b8689d890dfb495081f7be9b9e257f7a2df (diff)
downloadblackbird-op-linux-a21d45726acacc963d8baddf74607d9b74e2b723.tar.gz
blackbird-op-linux-a21d45726acacc963d8baddf74607d9b74e2b723.zip
tcp: avoid order-1 allocations on wifi and tx path
Marc Merlin reported many order-1 allocations failures in TX path on its wireless setup, that dont make any sense with MTU=1500 network, and non SG capable hardware. After investigation, it turns out TCP uses sk_stream_alloc_skb() and used as a convention skb_tailroom(skb) to know how many bytes of data payload could be put in this skb (for non SG capable devices) Note : these skb used kmalloc-4096 (MTU=1500 + MAX_HEADER + sizeof(struct skb_shared_info) being above 2048) Later, mac80211 layer need to add some bytes at the tail of skb (IEEE80211_ENCRYPT_TAILROOM = 18 bytes) and since no more tailroom is available has to call pskb_expand_head() and request order-1 allocations. This patch changes sk_stream_alloc_skb() so that only sk->sk_prot->max_header bytes of headroom are reserved, and use a new skb field, avail_size to hold the data payload limit. This way, order-0 allocations done by TCP stack can leave more than 2 KB of tailroom and no more allocation is performed in mac80211 layer (or any layer needing some tailroom) avail_size is unioned with mark/dropcount, since mark will be set later in IP stack for output packets. Therefore, skb size is unchanged. Reported-by: Marc MERLIN <marc@merlins.org> Tested-by: Marc MERLIN <marc@merlins.org> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_output.c')
-rw-r--r--net/ipv4/tcp_output.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 364784a91939..376b2cfbb685 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2060,7 +2060,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
/* Punt if not enough space exists in the first SKB for
* the data in the second
*/
- if (skb->len > skb_tailroom(to))
+ if (skb->len > skb_availroom(to))
break;
if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
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