ServerBuddies Support Blog

Linux performance tuning -vm.swappiness

Linux kernel has improved memory subsystem, with which administrators now have a simple interface to fine-tune the swapping behavior of the kernel.  The linux kernel tunable parameter vm.swappiness (/proc/sys/vm/swappiness) can be used to define how aggressively memory pages are swapped to disk.

Linux moves memory pages that have not been accessed for some time to the swap space even if there is enough free memory available. By changing the percentage in /proc/sys/vm/swappiness you can control the swapping behavior, depending on the system configuration.

A high swappiness value means that the kernel will be more apt to unmap mapped pages. A low swappiness value means the opposite, the kernel will be less apt to unmap mapped pages. In other words, the higher the vm.swappiness value, the more the system will swap.

Performance Improved in cPanel 11.25 DNS Clustering

cPanel DNS clustering utility, DNSAdmin, now sends updates in batches with a single call, reducing the server’s memory consumption during DNS synchronization.

cPanel have also added a feature that will automatically disable unresponsive cluster members, preventing outdated information from being sent to up-to-date servers when the unresponsive server come back online. Plus, cPanel simplified reconfiguring and restarting BIND into a single call, speeding up the process.