Re: [Flightgear-devel] Defaulting /sim/rendering/database-pager/threads to 4

[James T. <ja...@fl...>]

> On 30 Jan 2023, at 15:57, TheFGFSEagle <the...@gm...> wrote:
> 
> Do you think setting the threads count to 4 is a good idea? I mean, not everyone (including me) has 4 cores, and if we have 2 threads per core, that might degrade performance rather than increase it, right ? I don't know much about threading etc., so sorry if I'm talking nonsense.
> 

The issue is if the threads are IO constrained or CPU constrained : I suspect the pager threads are not CPU constrained for most people, but they do have phases that might be (the BVH building and effect-node building). Even if you only have dual cores, I’d suspect 4 pager threads would be give better over utilisation than 2, but as ever, this is a guess, needs real testing, blah blah :)

This is also why I’d ask if the goal here is experimentation / data-collection or an end user UI: if we do lots of experimentation, we might discover a good heuristic is ‘number of CPU cores * 2’ or ‘number of CPU cores * 1.5, rounded down’. At which point the UI should probably be:

	[*] automatically select threads used for loading scenery
	[  ] use [NNNNN] threads for loading scenery 

(where NNNN is a numerical edit box, or similar, and the first option uses the best heuristic we can find)

With the new GUI system (!!) we could even do a mode which opens the property inspector at a particular branch of the property tree, and have a:

	[*] manually select loading settings [click here to edit values]

… to keep the power tweakers happy without having a custom dialog box for every set of properties. (We do need to ensure they get auto-saved though, for this UI flow to be non-annoying)

Kind regards,
James