Created attachment 138436 [details]
System Load Viewer in Plasma 5.18

This feature request/report was borne out of the discussion in https://invent.kde.org/plasma/kdeplasma-addons/-/merge_requests/68, which itself was a result of System Load Viewer being 'killed' off in https://invent.kde.org/plasma/kdeplasma-addons/-/merge_requests/27. It appears System Load Viewer is no longer desirable and future use/development should be on this System Monitor widget instead, which unfortunately does not (yet) quite match the old viewer in terms of appearance nor functionality.

Summary:
1. Restore ability to configure update interval (refresh rate of the viewer).
2. Restore Compact Bar view.

For point 1, this should be self-explanatory.

For point 2, this involves a number of things:
* Compact Bar greatly reduces the space taken by the widget (very important, for example, with CPUs with many cores/threads, such as Threadripper).
* The System Monitor uses colour only to represent different cores/threads, but the old System Load Viewer used consistent colours to represent user/system/nice/io CPU usage per core/thread which provides much more information in less space.
* Additionally, while the old System Load Viewer showed both CPU and Memory usage together in one widget, replicating this functionality with System Monitor requires at least two widgets - one for CPU and one for Memory - with the latter taking up far too much room in terms of width (I recognise pie chart is the default). Likewise with CPU, it only shows overall memory usage and does not distinguish between application data and disk buffers/cache. At least allow the bar chart view to use less space if there's only a single data point, or perhaps allow for configurable width.

This report may well be a duplicate of, or at least overlap with, https://bugs.kde.org/show_bug.cgi?id=437114

Kubuntu 20.04 vs 21.04
Plasma 5.18 vs 5.21