> How do I write a program that will ask the kernel how much free
> physical memory there is available to me without causing a lot of
> swapping?
In "the old days" experiments showed that the syscall overhead was
negligibly different for 8k I/O buffers vs. 64k buffers. Nowadays you
can just use 1M buffers and assume the system can deal with it. Can
you really show that operating on 8M buffers gives you noticably
better performance than 1M buffers?