Agreed. There are a lot of other possible optimizations, from the often-mentioned buffer size settings:

  net.core.rmem_max / net.core.wmem_max
  net.ipv4.tcp_rmem / net.ipv4.tcp_wmem

to metric tunings like:

  net.ipv4.tcp_no_metrics_save / net.ipv4.tcp_moderate_rcvbuf

I've been playing around with these settings on very loaded machines:

  # Retry SYN/ACK only three times, instead of five
  net.ipv4.tcp_synack_retries = 3
  # Try to close things only twice
  net.ipv4.tcp_orphan_retries = 2
  # FIN-WAIT-2 for only 5 seconds
  net.ipv4.tcp_fin_timeout = 5
  # Increase syn socket queue size (default: 512)
  net.ipv4.tcp_max_syn_backlog = 2048
  # One hour keepalive with fewer probes (default: 7200 & 9)
  net.ipv4.tcp_keepalive_time = 3600
  net.ipv4.tcp_keepalive_probes = 5
  # Max packets the input can queue
  net.core.netdev_max_backlog = 2500
  # Keep fragments for 15 sec (default: 30)
  net.ipv4.ipfrag_time = 15
  # Use H-TCP congestion control
  net.ipv4.tcp_congestion_control = htcp