[CM] file ops

Kjetil Svalastog Matheussen k.s.matheussen@notam02.no
Fri, 25 May 2007 16:35:12 +0200 (CEST)

On Fri, 25 May 2007, Bill Schottstaedt wrote:

> Since several people seem to be worrying about disk accesses --
> I think that modern OS's (linux in particular) 
> automatically cache files in RAM -- what appear to be disk ops are
> actually references to memory.  In the bad old days you had to use
> mmap or something -- I forget how it used to work. 
> This info itself may be out-of-date -- I am not an OS wizard!
> My first thought when I hear about dropouts is not "disk ops", but
> "garbage collection", and then "X server traffic", and then "some
> background process".   I believe the latter is one thing that
> Fernando's real-time kernel deals with.  And Motif generates
> at least an order of magnitude less X traffic than Gtk. 
> As I say, I don't actually know anything...

Yes, garbage collecting and gtk traffic is what I have found to be the two 
largest causes for dropouts in snd as well.

But if the sound processing had been handled in a seperate high priority
thread instead, it would have been possible to increase buffer size
without getting high response time as well, which is what the
<snd-rt-player> instrument does. The <snd-rt-player> instrument does use
some more memory though, but memory is cheap.