On Fri, Dec 12, 2008 at 11:12:46AM +0530, Balbir Singh wrote:
> * Dhaval Giani <[email protected]> [2008-12-12 10:06:06]:
> 
> > On Fri, Dec 12, 2008 at 09:59:54AM +0530, Balbir Singh wrote:
> > > * Dhaval Giani <[email protected]> [2008-12-12 09:47:13]:
> > > 
> > > > On Fri, Dec 12, 2008 at 02:53:44AM +0530, Balbir Singh wrote:
> > > > > Hi, All,
> > > > > 
> > > > > As discussed in the previous thread
> > > > > http://article.gmane.org/gmane.comp.lib.libcg.devel/139, we don't have
> > > > > the concept of default groups and tasks should be able to return back
> > > > > to their default group when done.
> > > > > 
> > > > > Here is a fix to the cgconfig script to fix the issue. Please review,
> > > > > comment on it.
> > > > > 
> > > > > Signed-off-by: Balbir Singh <[email protected]>
> > > > > 
> > > > > Index: scripts/init.d/cgconfig
> > > > > ===================================================================
> > > > > --- scripts/init.d/cgconfig   (revision 225)
> > > > > +++ scripts/init.d/cgconfig   (working copy)
> > > > > @@ -82,6 +82,56 @@
> > > > >                  #log_progress_msg "Starting cgconfig service: "
> > > > >                  cgconfigparser -l $CONFIG_FILE
> > > > >          fi
> > > > > +
> > > > > +        declare defaultcgroup
> > > > > +
> > > > > +        if [ -f /etc/cgrules.conf ]
> > > > > +        then
> > > > > +            read user ctrl defaultcgroup <<< \
> > > > > +                `grep -m1 ^\* /etc/cgrules.conf`
> > > > > +            if [[ -n $defaultcgroup && $defaultcgroup = "*" ]]
> > > > > +            then
> > > > > +                log_warning_msg "/etc/cgrules.conf incorrect"
> > > > > +                log_warning_msg "Overriding it"
> > > > > +                defaultcgroup=
> > > > > +            fi
> > > > > +        fi
> > > > > +
> > > > > +        if [ -z $defaultcgroup ]
> > > > > +        then
> > > > > +            defaultcgroup=sysdefault/
> > > > > +        fi
> > > > > +        #
> > > > > +        # Create a default class for tasks to return back to
> > > > > +        #
> > > > > +        parse_mounts
> > > > > +        for i in `seq 1 $maxindex`
> > > > > +        do
> > > > > +            #
> > > > > +            # Ignore if directory already exists
> > > > > +            #
> > > > > +            mkdir ${MOUNTPOINT[$i]}/$defaultcgroup 2> /dev/null
> > > > > +            chmod a+rw ${MOUNTPOINT[$i]}/$defaultcgroup/tasks
> > > > > +            #
> > > > > +            # special rule for cpusets
> > > > > +            #
> > > > 
> > > > Need a special rule for the group scheduler. You will not be able to
> > > > move in real time tasks into defaultcgroup.
> > > >
> > > 
> > > I expermented and tried with that, my movement fails already, which is
> > > expected. What special rule do we need?
> > > 
> > 
> > You will need to setup a non-zero cpu.sched_rt_runtime_us, but it is not
> > as simple as just copying the value from the parent (because than other
> > groups will not get any rt time)
> >
> 
> In that case, I'll let the system administrator setup
> cpu.sched_rt_runtime_us, if they really care to make sure that RT
> tasks should migrate to the default group. Otherwise, all RT tasks
> stay in root.
> 
> The combinations of controllers and their semantics are getting out of
> hand (honestly). This I think is a fair trade-off.
> 

:-)

We do need a solution though. Even the layer 2 APIs need to have this in
mind. I am working on those APIs, and a couple of other problems have
cropped up. I will probably post those APIs as an RFC very soon, and ask
for some design help then.

thanks,
-- 
regards,
Dhaval

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