Hi Kouichi, In general I would discourage use of compile contexts except for very narrow usage models. The main issue comes down to shadred contexts having the potential for conflicts when reading/writing to shared GL objects. The OSG doesn't have mutexes built into access of GL objects so can only do shared context/compile context if no GL objects will be accessed by the two contexts concurrently. Adding such mutexes would add a huge burden on all OSG applications.
Robert. On 7 November 2015 at 23:29, Kouichi Yoshizawa < [email protected]> wrote: > Hello, > > I would like to learn the status of shared compile context threads in > OpenSceneGraph, as I would like to make use of them for performance > reasons. My platform is Linux with Nvidia Quadro GPUs that should have > good support for shared contexts for GPU transfers. > > In 2010 Robert Osfield seems to suggest that shared compile contexts are > indeed supported by OSG, although GPU hardware/driver support might be > lacking: > > > > I implemented them [ie shared compile contexts] under Linux with NVidia > drivers and they worked as expected, but with other drivers and other OS's > reports back from the community haven't been so positive, so it looks like > it's a feature that driver developers don't put much effort in to make sure > it's solid. > > > However, in 2014 he seems to be discouraging their use, maybe due to > thread safety issues in OSG, or am I reading this wrong? > > > > The OSG's is written to handling multi-theading of shared contexts as > > handling this special case would require us to add lots of mutex locks > > to all OpenGL code that is setting or using OpenGL objects. > > > > It's better to avoid shared contexts. > > > > > Inspecting the source code, of particular concern to me is the > creation/deletion of GL objects. It appears that the GL object orphan list > is accessed without mutual exclusion, from the flush functions as well as > the orphan reuse functions during object creation. Therefore these two > operations must then never be performed in different threads, but if they > are only called from the same thread (the compile context thread in my > case) is thread safety then guaranteed? I would be very grateful for > clarifications regarding this. > > Thank you! > > Cheers, > Kouichi[/quote] > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=65576#65576 > > > > > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org >
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