On 10/28/2010 09:24 AM, Avi Kivity wrote: > On 10/28/2010 01:54 PM, Ian Molton wrote: >>> Well, I like to review an implementation against a spec. >> >> >> True, but then all that would prove is that I can write a spec to >> match the code. > > It would also allow us to check that the spec matches the > requirements. Those two steps are easier than checking that the code > matches the requirements. I'm extremely sceptical of any GL passthrough proposal. There have literally been half a dozen over the years and they never seem to leave proof-of-concept phase. My (limited) understanding is that it's a fundamentally hard problem that no one has adequately solved yet. A specifically matters an awful lot less than an explanation of how the problem is being solved in a robust fashion such that it can be reviewed by people with a deeper understanding of the problem space. Regards, Anthony Liguori >> The code is proof of concept. the kernel bit is pretty simple, but >> I'd like to get some idea of whether the rest of the code will be >> accepted given that theres not much point in having any one (or two) >> of these components exist without the other. > > I guess some graphics people need to be involved. > >> >>> Better, but still unsatisfying. If the server is busy, the caller would >>> block. I guess it's expected since it's called from ->fsync(). I'm not >>> sure whether that's the best interface, perhaps aio_writev is better. >> >> The caller is intended to block as the host must perform GL rendering >> before allowing the guests process to continue. > > Why is that? Can't we pipeline the process? > >> >> The only real bottleneck is that processes will block trying to >> submit data if another process is performing rendering, but that will >> only be solved when the renderer is made multithreaded. The same >> would happen on a real GPU if it had only one queue too. >> >> If you look at the host code, you can see that the data is already >> buffered per-process, in a pretty sensible way. if the renderer >> itself were made a seperate thread, then this problem magically >> disappears (the queuing code on the host is pretty fast). > > Well, this is out of my area of expertise. I don't like it, but if > it's acceptable to the gpu people, okay. > >> >> In testing, the overhead of this was pretty small anyway. Running a >> few dozen glxgears and a copy of ioquake3 simultaneously on an intel >> video card managed the same framerate with the same CPU utilisation, >> both with the old code and the version I just posted. Contention >> during rendering just isn't much of an issue. > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
