Collectl is a lightweight performance monitoring tool capable of reporting interactively as well as logging to disk. It reports statistics on cpu, disk, infiniband, lustre, memory, network, nfs, process, quadrics, slabs and more in easy to read format. Read more
ExtreMon is a tool that allows you to visualize the CollectD output as things are happening, in a full-screen fully customizable visualization of the data.
netdata is a highly optimized Linux daemon providing real-time performance monitoring for Linux systems, Applications, SNMP devices, over the web!
perf began as a tool for using the performance counters subsystem in Linux, and has had various enhancements to add tracing capabilities.
Upsilon is a distributed, flexible and extensible system monitoring application.
WhoisUP monitors hosts via ICMP and shows the status in a web page. When a host is down, the script can send mail, syslog message, open a popup message or play a sound.
Moreover, the script checks if the host exceeds the latency threshold limit.