The below shell command can be used to check the amount of RAM in Ubuntu Linux.
$ dmesg | grep -in available | grep -in memory
The above command will show output similar to below line
3:150:[ 0.000000] Memory: 943092K/1044960K available
This line shows the amount to RAM installed on the system and usable RAM in Kilobytes.
TCP Selective Acknowledgment (SACK) has to be disabled on the Linux kernel. TCP Selective Acknowledgment (SACK) is used to improve performance of data transfer on TCP stack.
When TCP SACK is enabled the TCP packet capture will have TCP options similar to below screenshot
Disable TCP SACK
To disable SACK run the below command on Linux cli as root.
# sudo echo “net.ipv4.tcp_sack = 0” >> /etc/sysctl.conf
# sudo sysctl -p
After running the above commands the Linux server needs to be rebooted to apply the new configuration.
Once the server is rebooted the Linux server will not do TCP SACK any more.
Disabling TCP SACK will negatively effect the data transfer performance. The magnitude of performance hit depends on type of data transfer.