Our new MC has a view of all the requests for all the clients over time. The "longer" the time view, the greater the latency the clients see but the higher the BW is (due to more efficient requests re-ordering). The MC also looks at the DRAM activity and settings, and since it can "look" into the future for all clients, it can be told different algorithms and parameters to help it decide how to best make use of the available BW.
As well, the MC gets direct feedback from all clients as to their "urgency" level (which refers to different things for different client, but, simplifying, tells the MC how well they are doing and how much they need their data back), and adjusts things dynamically (following programmed algorithms) to deal with this. Get feedback from the DRAM interface to see how well it's doing too.
We are able to download new parameters and new programs to tell the MC how to service the requests, which clients's urgency is more important, basically how to arbitrate between over 50 clients to the dram requests. The amount of programming available is very high, and it will take us some time to tune things.
In fact, we can see that per application (or groups of applications), we might want different algorithms and parameters. We can change these all in the driver updates. The idea is that we, generally, want to maximize BW from the DRAM and maximize shader usage. If we find an app that does not do that, we can change things. You can imagine that AA, for example, changes significantly the pattern of access and the type of requests that the different clients make (for example, Z requests jump up drastically, so do rops). We need to re-tune for different configs. In this case, the OGL was just not tuning AA performance well at all. We did a simple fix (it's just a registry change) to improve this significantly. In future drivers, we will do a much more proper job.
