Changeset 2457 in orxonox.OLD

Automatically added by cvs2svntracking:
Date: 2004-09-13 22:48
Author: kpreslan
This should be a fix for bug #126531.

The issue has to do with the fact that GFS locking is only invoked by
a mmap during the page fault. There is no way for GFS to know that
the process causing the page fault has finished reading or writing to
the page for now. The way GFS has worked in the past is that as soon
as the page fault has completed, the lock protecting the file is
available to be demoted or dropped at the request of a callback from
another machine. This means that a newly faulted-in page could get
yanked out from under a process before it gets a chance to do
sufficient work on the page.

This checking provides a way for the page fault code to make a
machine be greedy with a lock for a certain period of time. This
means that after the fault, GFS will ignore callbacks for a certain
period of time. After that time, GFS will respond to any callbacks
that have arrived and then mark the files lock as being able to be
made greedy again. The code is setup so that the amount of time that
the lock is marked greedy is dependent on how much page faults traffic
there is on that file. When there is a lot of traffic, the time
increases. When there is a little traffic, the time decreases.