Modify TCP tuning settings in the networking module.

Signed-off-by: Hans Persson <hans@nsc.liu.se>

manifests/tcptuning/if10g.pp

@@ -2,13 +2,18 @@ class networking::tcptuning::if10g
 {
     sysctl {
 	# Increase TCP max buffer size settable using setsockopt().
+	#
 	# Bandwidth-in-bits-per-second * Round-trip-latency-in-seconds / 8 =
-	# TCP window size in bytes = 10000000000 * 60 / 8 = 75000000000
-	'net.core.rmem_max': value => '75000000';
-	'net.core.wmem_max': value => '75000000';
+	# TCP window size in bytes
+	#
+	# Calculate for 1Gbps and 30ms roundtrip time according to ping:
+	# 10000000000 * 0.030 / 8 = 37500000
+	#
+	'net.core.rmem_max': value => '37500000';
+	'net.core.wmem_max': value => '37500000';
 	# Increase Linux autotuning TCP buffer limit.
-	'net.ipv4.tcp_rmem': value => '4096 87380 75000000';
-	'net.ipv4.tcp_wmem': value => '4096 87380 75000000';
+	'net.ipv4.tcp_rmem': value => '4096 87380 37500000';
+	'net.ipv4.tcp_wmem': value => '4096 87380 37500000';
 	# Increase the length of the processor input queue.
 	'net.core.netdev_max_backlog': value => '30000';
     }

manifests/tcptuning/if1g.pp

@@ -2,13 +2,18 @@ class networking::tcptuning::if1g
 {
     sysctl {
 	# Increase TCP max buffer size settable using setsockopt().
+	#
 	# Bandwidth-in-bits-per-second * Round-trip-latency-in-seconds / 8 =
-	# TCP window size in bytes = 1000000000 * 60 / 8 = 7500000000
-	'net.core.rmem_max': value => '7500000';
-	'net.core.wmem_max': value => '7500000';
+	# TCP window size in bytes
+	#
+	# Calculate for 1Gbps and 30ms roundtrip time according to ping:
+	# 1000000000 * 0.030 / 8 = 3750000
+	#
+	'net.core.rmem_max': value => '3750000';
+	'net.core.wmem_max': value => '3750000';
 	# Increase Linux autotuning TCP buffer limit.
-	'net.ipv4.tcp_rmem': value => '4096 87380 7500000';
-	'net.ipv4.tcp_wmem': value => '4096 87380 7500000';
+	'net.ipv4.tcp_rmem': value => '4096 87380 3750000';
+	'net.ipv4.tcp_wmem': value => '4096 87380 3750000';
 	# Increase the length of the processor input queue.
 	'net.core.netdev_max_backlog': value => '30000';
     }

manifests/tcptuning/if40g.pp

@@ -2,13 +2,18 @@ class networking::tcptuning::if40g
 {
     sysctl {
 	# Increase TCP max buffer size settable using setsockopt().
+	#
 	# Bandwidth-in-bits-per-second * Round-trip-latency-in-seconds / 8 =
-	# TCP window size in bytes = 10000000000 * 60 / 8 = 75000000000
-	'net.core.rmem_max': value => '75000000';
-	'net.core.wmem_max': value => '75000000';
+	# TCP window size in bytes
+	#
+	# Calculate for 40Gbps and 30ms roundtrip time according to ping:
+	# 40000000000 * 0.030 / 8 = 150000000
+	#
+	'net.core.rmem_max': value => '150000000';
+	'net.core.wmem_max': value => '150000000';
 	# Increase Linux autotuning TCP buffer limit.
-	'net.ipv4.tcp_rmem': value => '4096 87380 75000000';
-	'net.ipv4.tcp_wmem': value => '4096 87380 75000000';
+	'net.ipv4.tcp_rmem': value => '4096 87380 150000000';
+	'net.ipv4.tcp_wmem': value => '4096 87380 150000000';
 	# Increase the length of the processor input queue.
 	'net.core.netdev_max_backlog': value => '30000';
     }