Re: [Flightgear-devel] Flight gear not utilising all cores of processor during initialisation

[Stuart B. <stu...@gm...>]

Hi Folks,

I've been spending a bit of time digging into the OSG DatabasePager as part
of the WS3.0 work. It's all a bit complicated, and I  behaviour has changed
since 2020.3

The OSG_NUM_DATABASE_THREADS and OSG_NUM_HTTP_DATABASE_THREADS
environmental can be used to set the number of threads used to load
objects, scenery etc.  The first is the total number of threads, and the
latter is the subset of those threads that are used for HTTP.  (I agree
that's not at all obvious - see OSG osgDB/DatabasePager.cxx line 1209)

(wkitty - setting both to 7 as you have below would result in just one
threads being created for general loading, which I don't think was your
intention.  I think you'd want OSG_NUM_DATABASE_THREADS=7 and
OSG_NUM_HTTP_DATABASE_THREADS=0)

That said, neither of the variables are relevant on next because FG
explicitly sets the number of threads in fg_init (I haven't checked
2020.3). I recently added code to next to support using
/sim/rendering/database-pager/threads to set the number of threads.  Note
that this is again the total threads, and one of those will we still set up
a single HTTP thread.  I suspect we should simply set the number of HTTP
threads to 0, as we don't use them.

-Stuart

PS: We also have separate threads for TTS, terrasync.
/sim/rendering/multithreading-mode can also be set for extra performance
and threading related crashes in OSG for the brave/foolhardy ;)