> There should definitely be a nice API for an in-kernel AltiVec context > save/restore. When preemption happens doesn't it do some equivalent of > the userspace context switch? Why can't the preemption system take care > of it? > > At worst case you make the worst case latency bigger, but at best case > you gain performance across the board.
Do you ? Can you prove this assertion with numbers ? > One thing which is worrying me is that now that Ben has thrown down the > gauntlet (note, I'm not going to be coding a line, but I know a man who > can :) how on earth do we benchmark the differences here? Precisely :-) So again, let's start by having somebody pick up something that you believe is worth altivec-ifying, eat the preempt_disable/enable for now, and if we see that indeed, it's worth the pain, then we can look into adding a way to context switch altivec in a kernel thread upon explicit request or something like that. As to how to benchmark the difference ? Well, I would suggest first a couple of very simple things that give a good indication, and from there, if it looks promising, we can torture more and see whether we can find regressions etc.. For example, I personally use kernel compile times (with make -jN on SMP), I find it a good overall exercise, but if you feel like a network benchmark might be better at advertising your improvements, then go for that too, though expect us to also do some other tests to verify they didn't regress. Cheers, Ben. _______________________________________________ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
