On Mon, Mar 17, 2003 at 04:23:46PM +0100, Johnny Billquist wrote:

 > Like I said, I haven't really checked anything up, it's just some
 > semi-unqualified guessing.
 > 
 > Since you probably know for sure, you might as well settle this once and
 > for all. Is the file caching totally zero-copy stuff?

Right, the data is DMA'd directly into the cache page if the controller
can do DMA.

Note that in UBC, the cache isn't something bolted onto the side; it's
fundamentally a part of how all file I/O works.

 > If so, do you have any other good ideas why I see peaks of over 70% system
 > time when running build.sh. (And this is not when running gcc).

You could be paging a lot; see my comment about bad defaults on small-memory
machines.  Search the mailing list archives for a post from Simon Burge
on the subject.

-- 
        -- Jason R. Thorpe <thorpej@wasabisystems.com>