Re: problems with mbuff in rtlinux-2.3

[Ray <rehenry-at-up.net>]

On Tue, 17 Oct 2000, eric wrote:
> Ray wrote:
> 
> > mbuff hangs into the kernel very often here and will sometimes cause
> > massive slowdowns and overwork on my system.  In fact my observation of
> > this problem is the only reason I would not recommend any 2.?.? version of
> > rtlinux and EMC as a stable production CNC.
> 
> This is very interesting, I get the impression that lots of the rtl
> developers
> out there are using mbuff with a reasonable amount of success.  I need
> to use
> it myself for my hydraulic fatigue testing machine controller, so i will
> have
> to look into it.
> How can you tell that it is hanging you up?  

I first found it with lsmod.  More recently, I added lines to the cleanup
process in the run script that removes the rt modules.  These lines 
reports whether or not the rt modules were cleaned out the last time.

>The thing that it may do is
> produce 
> memory starved system, since it allocates memory that can't be paged out
> to disk.
> Then all the other programs will get paged a lot more...

I wish that I knew more about how to troubleshoot this thing when it
happens!  I posted notes on this a while back and got some suggestions but
couldn't find a specific error.  The ownership of mbuff seems to get
transfered to some dummy process when EMC shuts down.

Ray