[RFC PATCH 4/5] Adjust alpha according to RTT timing

[Baruch Even <baruch@xxxxxxxxx>]

Do RTT scaling on alpha.

Signed-Off-By: Douglas Leith <doug.leith@xxxxxxx>
Signed-Off-By: Baruch Even <baruch@xxxxxxxxx>

Index: 2.6.12-rc/net/ipv4/tcp_input.c
===================================================================
--- 2.6.12-rc.orig/net/ipv4/tcp_input.c
+++ 2.6.12-rc/net/ipv4/tcp_input.c
@@ -107,6 +107,7 @@ int sysctl_tcp_htcp = 1;
 int sysctl_tcp_htcp_modeswitch = 1;
 int sysctl_tcp_htcp_alpha_func = 1;
 int sysctl_tcp_htcp_alpha_adjust = 1;
+int sysctl_tcp_htcp_rtt_scaling = 1;
 
 #define FLAG_DATA              0x01 /* Incoming frame contained data.          
*/
 #define FLAG_WIN_UPDATE                0x02 /* Incoming ACK was a window 
update.       */
@@ -2132,6 +2133,16 @@ static inline void reno_cong_avoid(struc
                                }
                        }
 
+                       if (sysctl_tcp_htcp_rtt_scaling) {
+                               __u32 RTT_Scaling;
+                               /* refer current RTT to design point, clamping 
ratio to interval [0.5,10] */
+                               RTT_Scaling = 
max((HZ<<3)/(10*tp->htcp.snd_minRTT), (__u32)1<<2);
+                               RTT_Scaling = min(RTT_Scaling,(__u32)10<<3);
+                               alpha = (alpha<<3)/RTT_Scaling;
+                               if (!alpha)
+                                       alpha = 1;
+                       }
+
                        if (sysctl_tcp_htcp_alpha_adjust) {
                                alpha = alpha*2*((1<<7)-tp->htcp.snd_beta);
                                if (!alpha)
Index: 2.6.12-rc/net/ipv4/sysctl_net_ipv4.c
===================================================================
--- 2.6.12-rc.orig/net/ipv4/sysctl_net_ipv4.c
+++ 2.6.12-rc/net/ipv4/sysctl_net_ipv4.c
@@ -722,6 +722,14 @@ ctl_table ipv4_table[] = {
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,
        },
+       {
+               .ctl_name       = NET_TCP_HTCP_RTT_SCALING,
+               .procname       = "tcp_htcp_rtt_scaling",
+               .data           = &sysctl_tcp_htcp_rtt_scaling,
+               .maxlen         = sizeof(int),
+               .mode           = 0644,
+               .proc_handler   = &proc_dointvec,
+       },
        { .ctl_name = 0 }
 };
 
Index: 2.6.12-rc/include/linux/sysctl.h
===================================================================
--- 2.6.12-rc.orig/include/linux/sysctl.h
+++ 2.6.12-rc/include/linux/sysctl.h
@@ -350,6 +350,7 @@ enum
        NET_TCP_HTCP_MODESWITCH=110,
        NET_TCP_HTCP_ALPHA_FUNC=111,
        NET_TCP_HTCP_ALPHA_ADJUST=112,
+       NET_TCP_HTCP_RTT_SCALING=113,
 };
 
 enum {
Index: 2.6.12-rc/include/net/tcp.h
===================================================================
--- 2.6.12-rc.orig/include/net/tcp.h
+++ 2.6.12-rc/include/net/tcp.h
@@ -616,6 +616,7 @@ extern int sysctl_tcp_htcp;
 extern int sysctl_tcp_htcp_modeswitch;
 extern int sysctl_tcp_htcp_alpha_func;
 extern int sysctl_tcp_htcp_alpha_adjust;
+extern int sysctl_tcp_htcp_rtt_scaling;
 
 extern atomic_t tcp_memory_allocated;
 extern atomic_t tcp_sockets_allocated;