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authorDaniel Borkmann <dborkman@redhat.com>2013-06-19 12:51:20 +0200
committerDavid S. Miller <davem@davemloft.net>2013-06-19 21:16:53 -0700
commiteea86af6b1e18d6fa8dc959e3ddc0100f27aff9f (patch)
treea8f200392d1671a058311009aa360226c22b5da8 /include/net/sock.h
parentdc25c676f54addb10e598daa9da9b8dd4fd487ab (diff)
net: sock: adapt SOCK_MIN_RCVBUF and SOCK_MIN_SNDBUF
The current situation is that SOCK_MIN_RCVBUF is 2048 + sizeof(struct sk_buff)) while SOCK_MIN_SNDBUF is 2048. Since in both cases, skb->truesize is used for sk_{r,w}mem_alloc accounting, we should have both sizes adjusted via defining a TCP_SKB_MIN_TRUESIZE. Further, as Eric Dumazet points out, the minimal skb truesize in transmit path is SKB_TRUESIZE(2048) after commit f07d960df33c5 ("tcp: avoid frag allocation for small frames"), and tcp_sendmsg() tries to limit skb size to half the congestion window, meaning we try to build two skbs at minimum. Thus, having SOCK_MIN_SNDBUF as 2048 can hit a small regression for some applications setting to low SO_SNDBUF / SO_RCVBUF. Note that we define a TCP_SKB_MIN_TRUESIZE, because SKB_TRUESIZE(2048) adds SKB_DATA_ALIGN(sizeof(struct skb_shared_info)), but in case of TCP skbs, the skb_shared_info is part of the 2048 bytes allocation for skb->head. The minor adaption in sk_stream_moderate_sndbuf() is to silence a warning by using a typed max macro, as similarly done in SOCK_MIN_RCVBUF occurences, that would appear otherwise. Suggested-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/sock.h')
-rw-r--r--include/net/sock.h15
1 files changed, 9 insertions, 6 deletions
diff --git a/include/net/sock.h b/include/net/sock.h
index 21db792bffa..ea6206ccc89 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2047,18 +2047,21 @@ static inline void sk_wake_async(struct sock *sk, int how, int band)
sock_wake_async(sk->sk_socket, how, band);
}
-#define SOCK_MIN_SNDBUF 2048
-/*
- * Since sk_rmem_alloc sums skb->truesize, even a small frame might need
- * sizeof(sk_buff) + MTU + padding, unless net driver perform copybreak
+/* Since sk_{r,w}mem_alloc sums skb->truesize, even a small frame might
+ * need sizeof(sk_buff) + MTU + padding, unless net driver perform copybreak.
+ * Note: for send buffers, TCP works better if we can build two skbs at
+ * minimum.
*/
-#define SOCK_MIN_RCVBUF (2048 + sizeof(struct sk_buff))
+#define TCP_SKB_MIN_TRUESIZE (2048 + sizeof(struct sk_buff))
+
+#define SOCK_MIN_SNDBUF (TCP_SKB_MIN_TRUESIZE * 2)
+#define SOCK_MIN_RCVBUF TCP_SKB_MIN_TRUESIZE
static inline void sk_stream_moderate_sndbuf(struct sock *sk)
{
if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) {
sk->sk_sndbuf = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
- sk->sk_sndbuf = max(sk->sk_sndbuf, SOCK_MIN_SNDBUF);
+ sk->sk_sndbuf = max_t(u32, sk->sk_sndbuf, SOCK_MIN_SNDBUF);
}
}