Re: Novice questions.

[Michael_Paremski@NGC.COM writes:]

> 1. How small is smallest delay, which I can make by VSTa system calls.

You mean the time to switch into the kernel from user mode? I think we had
numbers ages ago, but you may as well just measure it with a current model
CPU.

> 2. How I can get chunk of memory in physical address space more than
> 4K. I need it to build descriptors ring and buffer pool.

There is no code in the distribution to do this... the initial answer is to
see if your ring descriptors can accomodate scatter/gather of 4k pages. If
not, I have written some contiguous allocation code which I'd be happy to
supply.

> 3. How I can calculate physical address from virtual address.

In the kernel, vtop() does it. From user mode, see how the floppy driver
sets up for a DMA transfer using page_wire()/page_release().

> 4. Have anyone information how fast massage passing from kernel
> interrupt routine to driver.

Again, you should probably get current numbers. It was in the single digit
microsecond range, I think.

                                                        Andy
Received on Mon Sep 29 10:52:19 1997