feature update #5
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All the daemon creation/connection abstraction was extracted as a separate crate with_daemon and pidtree_mon now uses it as a dependency.
The previous algorithm would perfrom a measurement by collecting 2 samples of data from /proc some 100ms apart and comparing ticks used by various processes between the 2 samples, then cumulating the results over process trees. This didn't work very well for cases when the monitored processes spawned a lot of child processes that exited quickly, because: - about 90% of the information was lost during the wait - the reason a 100 ms interval was chosen in the first place was to lose as little information about spawned and killed processes as possible, while not having to update too frequently, but that meant an averaging window of 100ms, only once every 1000ms. - still, processes that both appeared and disappeared between 2 measurement points would get neglected, and so would the ticks consumed by processes that disappeared between measurements between the last measurement and the time the process disappeared. The new algorithm finally seems to account for all previously known problems, which was tested by comparing the output to the output of top/htop showing full CPU load when nothing much was running on the PC except for the measured process trees.
Now we are retrieving the time since boot in ticks instead of adding up ticks elapsed on all CPUs. This seems to have only one disadvantage: when running in a VM, this will not account for the time stolen by the host, so the calculated loads will be in relation to the one physical core, instead of one virtual core. At some point we might need a user option to control this behavior. Then we'll re-add the tick-counting code.
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