CpuMon

About CPU monitoring tools for Linux

This tools monitors CPU activity of a multi-core machine. This tools provides effective load report useful for debugging real-time software on common Posix operating system (tested on various OS such as Linux, FreeBSD and NetBSD).

Calibration process (usually on last core) can be done at start to obtain accurate measurements on non hyperthread CPU. However, calibration index is refine during all the program life time and store in a file (usually /var/lib/cpumon/calibration.txt on Linux or /var/cpumon/calibration.txt on *BSD systems) when exiting. Be careful that calibration will report bogus index on hyperthread CPU because of non homogeneous core speed. Then, a measurement process is launch on each core to estimate effective load and report this measure to a monitoring process assign to a specific core (first core). Consolidate measurement reports are displayed every 5 seconds.

Calibration

Calibration process is done if no calibration file exists, if calibration file contains unexpected value or if it force by user wishes. Calibration process need to schedule high priority real-time process to get accurate result on loaded computer; if cpumon is not owned by root, a degraded calibration is done instead. Anyway, calibration index is refined during every cycle. At the end, on user interrupt signal (ie Control-C), calibration index is be saved again.

Limits

Calibration process report bogus index on hyperthread processors, pleased avoid it when if the calculus convergence is slower.

No support for clock throttling CPU speed.

On NetBSD, bias could be close to 10% on certain (sic) load configuration.

On *BSD systems, pthread_setaffinity_np requires privileges. Only on NetBSD, ordinary users can be allowed to control CPU affinity via the security.models.extensions.user_set_cpu_affinity sysctl. On FreeBSD, one needs to be root to monitor CPU load.