instrumenting cache followup and request for info

[Brian Thomson]

>From nsc!chuqui ...

> Our 4.2 780 is still
> running DZ's using the dma simulation code. We are getting an enormous
> number of interrupts generated (with 8 DZ boards, who wouldn't???). Each
> interrupt seems to be dropping through the Swtch process scheduler routine,
> which sets up a new process for the CPU to play with.

Are you sure you're not mistaking idle time for "setting up a new process"?
The idle loop is in the Swtch routine.  On a 4.2 780 here, I once put
25000 chars/sec out through the DZ pseudo-DMA code and had cpu to spare.
-- 
		    Brian Thomson,	    CSRI Univ. of Toronto
		    {linus,ihnp4,uw-beaver,floyd,utzoo}!utcsrgv!uthub!thomson