ansible sysctl for ec2. perferrably used for 1g nics.

sysctl.yml

- hosts: localhost
  tasks:
    - name: update sysctl
      action: sysctl state=present reload=yes {{ item }}
      with_items:
      # max open files
      - name=fs.file-max value=65535
      # lets not use swap. 
      - name=vm.swappiness value=0
      # enable syn coockies. this can actually cause overhead.
      - name=net.ipv4.tcp_syncookies value=1
      # This allows reusing sockets in TIME_WAIT state for new connections when it is safe from protocol viewpoint.
      - name=net.ipv4.tcp_tw_reuse value=1
      # Max rx/tx buffer size (16M) - defaults high but can scale down.
      - name=net.core.rmem_max value=16777216
      - name=net.core.wmem_max value=16777216
      - name=net.core.rmem_default value=16777216
      - name=net.core.wmem_default value=16777216
      - name=net.ipv4.tcp_rmem value="4096 87380 16777216"
      - name=net.ipv4.tcp_wmem value="4096 65536 16777216"
      # Increase the maximum amount of option memory buffers // specifies the maximum buffer size allowed per socket.
      - name=net.core.optmem_max value=40960
      # Increase max number of sockets allowed in TIME_WAIT
      - name=net.ipv4.tcp_max_tw_buckets value=2000000
      # Increase max half-open connections
      - name=net.ipv4.tcp_max_syn_backlog value=30000
      # Increase max TCP orphans
      # These are sockets which have been closed and no longer have a file handle attached to them
      - name=net.ipv4.tcp_max_orphans value=262144
      # Max listen queue backlog
      - name=net.core.somaxconn value=4096
      # Max number of packets that can be queued on interface input
      # If kernel is receiving packets faster than can be processed
      # this queue increases
      - name=net.core.netdev_max_backlog value=50000
      # Only retry creating TCP connections twice
      # Minimize the time it takes for a connection attempt to fail
      - name=net.ipv4.tcp_synack_retries value=2
      - name=net.ipv4.tcp_syn_retries value=2
      # Timeout closing of TCP connections after 7 seconds
      - name=net.ipv4.tcp_fin_timeout value=7
      # Avoid falling back to slow start after a connection goes idle
      # keeps our cwnd(congestion window size) large with the keep alive connections
      - name=net.ipv4.tcp_slow_start_after_idle value=0
      # determines the number of probes before timing out
      - name=net.ipv4.tcp_keepalive_probes value=5
      # Determines the wait time between isAlive interval probes
      - name=net.ipv4.tcp_keepalive_intvl value=3
      # Disable TCP timestamps -- saves 12 bytes
      - name=net.ipv4.tcp_timestamps value=0
      # Selective acknowledgements - This option selectively acknowledges each segment in a TCP window.
      # This is especially good on very lossy connections (connections that loose a lot of data in the transfer)
      # since this makes it possible to only retransmit specific parts of the TCP window which lost data and not
      # the whole TCP window as the old standards told us to do.
      - name=net.ipv4.tcp_sack value=1
      # Enabling tcp window scaling 
      # Enabling tcp_window_scaling enables a special TCP option which makes it possible to scale these windows to a larger size,
      # and hence reduces bandwidth losses due to not utilizing the whole connection.
      - name=net.ipv4.tcp_window_scaling value=1
      # Causes the kernel to actively send RST packets when a service is overloaded. So no data is dropped.
      - name=net.ipv4.tcp_abort_on_overflow value=1