@Trent,
[quote user="Trent Rolf"] just as a gut feel, do you agree that that seems like a lot for just one biquad filter? Or does it seem reasonable?[/quote]
It is pretty hard to have an accurate guess without knowing what _blocksize is or how fast the processor is running or where everything is located relative to internal/external/cache for program and data.
One pass through the assembly code shown above would take about 40 CPU cycles if there were no stalls. The most common stalls come from memory accesses, and it is common to have caching disabled or data in the wrong location.
Our online training material is the best to find a more comprehensive list of things to do to get your code performing well. It would be good for us to be able to address questions you have from that material, and for you to see anything that might apply to your implementation.
Your benchmarking method may be including a lot of overhead. Have you tried replacing the biquad with a simple assignment out=in and see what the time measurements are?
Regards,
RandyP