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authorEric Dumazet <eric.dumazet@gmail.com>2012-03-18 11:07:47 +0000
committerDavid S. Miller <davem@davemloft.net>2012-03-19 16:53:08 -0400
commitc8628155ece363487b57d33441ea0359018c0fa7 (patch)
treea3a4e89d3f66208f4145bb2ed401e464474a8d9f /net/ipv4/proc.c
parente86b291962cbf477e35d983d312428cf737bc0f8 (diff)
downloadlinux-stericsson-c8628155ece363487b57d33441ea0359018c0fa7.tar.gz
tcp: reduce out_of_order memory use
With increasing receive window sizes, but speed of light not improved that much, out of order queue can contain a huge number of skbs, waiting to be moved to receive_queue when missing packets can fill the holes. Some devices happen to use fat skbs (truesize of 4096 + sizeof(struct sk_buff)) to store regular (MTU <= 1500) frames. This makes highly probable sk_rmem_alloc hits sk_rcvbuf limit, which can be 4Mbytes in many cases. When limit is hit, tcp stack calls tcp_collapse_ofo_queue(), a true latency killer and cpu cache blower. Doing the coalescing attempt each time we add a frame in ofo queue permits to keep memory use tight and in many cases avoid the tcp_collapse() thing later. Tested on various wireless setups (b43, ath9k, ...) known to use big skb truesize, this patch removed the "packets collapsed in receive queue due to low socket buffer" I had before. This also reduced average memory used by tcp sockets. With help from Neal Cardwell. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: H.K. Jerry Chu <hkchu@google.com> Cc: Tom Herbert <therbert@google.com> Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/proc.c')
-rw-r--r--net/ipv4/proc.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 02d61079f08b..8af0d44e4e22 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -257,6 +257,7 @@ static const struct snmp_mib snmp4_net_list[] = {
SNMP_MIB_ITEM("TCPReqQFullDoCookies", LINUX_MIB_TCPREQQFULLDOCOOKIES),
SNMP_MIB_ITEM("TCPReqQFullDrop", LINUX_MIB_TCPREQQFULLDROP),
SNMP_MIB_ITEM("TCPRetransFail", LINUX_MIB_TCPRETRANSFAIL),
+ SNMP_MIB_ITEM("TCPRcvCoalesce", LINUX_MIB_TCPRCVCOALESCE),
SNMP_MIB_SENTINEL
};