use jack :) then you don't have to care about that.
iiuc, the buffer size is in samples, and period defines how many buffers
are used - i guess this is per hardware interrupt, but i may be wrong.
high-end cards can do bufsize=32 and p=2. most cards should be able to
easily do 512/3. if latency is not an issue, you can use 4096/3 to save
cycles.