On Mon, Sep 04, 2006 at 09:26:22AM +0900, YAMAMOTO Takashi wrote:

> > But if that is
> > a problem, the feedback loop can be put into both vndread()/vndwrite().
> 
> why is it enough?

It is not enough, but it catches the case where the device is
accessed directly instead of through a filesystem.


> > >  I suspect
> > >  throttling the caller in vnd only hides the problem;
> > 
> > No, it prevents the problem. The writer needs to be throttled to
> > not overwhelm the consumer because in this case it just eats up
> > all memory. That necessary feedback loop is created by the patch.
> 
> can you explain how it prevents the problem while vndthread() already has
> the same check?

vndthread() does not have the same check. vndthread() is the consumer,
you have to stop the producer that allocates all the buffers.


> while vndthread is working on behalf of the pagedaemon here,
> it is not a pagedaemon.  so it can't get special treatment for pagedaemon
> from buffer cache etc and can deadlock.

In my case it is definitely not working on behalf of the pagedaemon.


Greetings,
-- 
                                Michael van Elst
Internet: mlelstv@serpens.de
                                "A potential Snark may lurk in every tree."