ipv4: Use binary search to choose tcp PMTU probe_size

Current probe_size is chosen by doubling mss_cache,
the probing process will end shortly with a sub-optimal
mss size, and the link mtu will not be taken full
advantage of, in return, this will make user to tweak
tcp_base_mss with care.

Use binary search to choose probe_size in a fine
granularity manner, an optimal mss will be found
to boost performance as its maxmium.

In addition, introduce a sysctl_tcp_probe_threshold
to control when probing will stop in respect to
the width of search range.

Test env:
Docker instance with vxlan encapuslation(82599EB)
iperf -c 10.0.0.24  -t 60

before this patch:
1.26 Gbits/sec

After this patch: increase 26%
1.59 Gbits/sec

Signed-off-by: Fan Du <fan.du@intel.com>
Acked-by: John Heffner <johnwheffner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 1085e12..e051d39 100644 (file)
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -87,6 +87,7 @@ struct netns_ipv4 {
        int sysctl_tcp_fwmark_accept;
        int sysctl_tcp_mtu_probing;
        int sysctl_tcp_base_mss;
+       int sysctl_tcp_probe_threshold;
 
        struct ping_group_range ping_group_range;
 

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 834089b..1ad82e3 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -67,6 +67,9 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
 /* The least MTU to use for probing */
 #define TCP_BASE_MSS           1024
 
+/* Specify interval when tcp mtu probing will stop */
+#define TCP_PROBE_THRESHOLD    8
+
 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 #define TCP_FASTRETRANS_THRESH 3
 

diff --cc net/ipv4/sysctl_net_ipv4.c
Simple merge

diff --cc net/ipv4/tcp_ipv4.c
Simple merge

diff --cc net/ipv4/tcp_output.c
Simple merge